Prof.
Michael Mueller-Preussker
(Humboldt-Universitaet zu Berlin)
23/06/2014, 11:15
Talk
Alexei Bazavov
(University of California/University of Iowa)
23/06/2014, 11:45
Talk
Kim Maltman
(York University, Toronto)
23/06/2014, 14:15
Talk
We propose a hybrid strategy for the lattice evaluation of the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon. The strategy combines direct numerical integration of lattice data for Q^2 greater than Q^2_min with the use of fit forms to handle the lattice data in the low-Q^2 region Q^2 less than Q^2_min. Using a physical model for the I=1...
Mr
David Scheffler
(TU Darmstadt)
23/06/2014, 14:15
We study chiral restoration and deconfinement in two-color QCD with two flavors of staggered quarks using a RHMC algorithm on GPUs. We measure the chiral condensate and the corresponding chiral susceptibility over the lattice coupling across the finite temperature transition. Using Ferrenberg-Swendsen reweighting we extract the maxima of the chiral susceptibility in order to determine...
Dr
Leonardo Cosmai
(INFN)
23/06/2014, 14:15
We present results on the curvature of the critical line of QCD with 2+1 HISQ fermions at nonzero temperature and quark density obtained by analytic continuation from imaginary chemical potentials. Monte Carlo simulations are performed by means of the MILC code suitably modified to include a nonzero imaginary baryon chemical potential. We set the chemical potential at the same value for the...
Dr
Donald Sinclair
(Argonne National Laboratory)
23/06/2014, 14:15
We perform lattice simulations gauge theories with fermions in non-fundamental representations of the gauge group, which might be models for Walking Technicolor theories. In particular we update results reported earlier on SU(3) gauge theory with colour-sextet quarks. In addition we will report on results (if any) obtained for SU(2) gauge theory with colour-adjoint fermions.
Dr
Mario Kieburg
(University Bielefeld)
23/06/2014, 14:15
A finite lattice spacing may have a crucial impact on the phase diagram of QCD. The existence of the Aoki phase for Wilson fermions underlines this point. Sharpe and Wu already showed that this kind of lattice artifacts carry over to finite twisted mass. The next task is the calculation of the phase diagram at finite chemical potential. I will present the phase diagram of Wilson fermions of...
Mr
Brendan Fahy
(Carnegie Mellon University)
23/06/2014, 14:15
Progress in calculating scattering phase shifts on Nf=2+1 anisotropic clover Wilson lattices is described. The stochastic LapH method facilitates computations in large volumes and for light pion masses. Results for pion masses down to 250 MeV, keeping m_pi L > 4, are presented.
Dr
Meifeng Lin
(Brookhaven National Laboratory)
23/06/2014, 14:35
Lattice QCD has entered the era of simulations directly at the physical quark masses thanks to the increasing computing power and algorithmic advancement. But the computational cost for such simulations is still extremely high, both for the gauge field generation and the measurements of physical observables. Adaptive multi grid (MG) algorithm has proven to be quite effective in reducing the...
Mr
Philipp Scior
(TU Darmstadt)
23/06/2014, 14:35
We compare SU(2) Polyakov loop models with different actions with data from full two-color QCD simulations around and above the critical Temperature [1,2].
We then apply the effective theory at finite temperature and density to
extract quantities like Polyakov loop correlators, effective Polyakov loop potentials and baryon density.
[1] Smith et al. , Phys. Rev. D88 (2013) 054020
[2]...
Derek Horkel
(University of Washington)
23/06/2014, 14:35
In this talk, I will summarize recent work with Prof. Stephen Sharpe in mapping out the phase diagram and pion spectrum for chiral perturbation theory with twisted-mass fermions in the presence of non-degeneracy between the up and down quark and discretization errors. I will show how the CP-violating phase of the continuum theory, which occurs for sufficiently large non-degeneracy, is...
Ms
Cynthia Yu-Han Huang
(National Chiao-Tung University, Taiwan)
23/06/2014, 14:35
We present the phase structure for SU(2) lattice gauge theory with 8 flavours of staggered fermions in the fundamental representation. One bulk phase transition is observed through the measurement of the plaquette, smeared Polyakov loops, as well as the Dirac operator eigenvalue spectrum. To further identify the order of the bulk phase transition pertaining to confinement and deconfinement, we...
Dr
Bastian Knippschild
(HISKP, University Bonn)
23/06/2014, 14:35
Pi-Pi scattering is investigated for the first time for N_f=2+1+1
dynamical quark flavours using Wilson twisted mass fermions. Lüschers
finite size method is used to relate energy shifts in finite volume
to scattering quantities like the scattering length in the I=2
channel. The computation is performed at several pion masses and lattice
spacings utilysing the stochastic LapH method,...
Michele Mesiti
(University of Pisa & INFN)
23/06/2014, 14:35
We present preliminary results regarding the curvature of the critical line of N_f = 2+1 QCD with physical quark masses. We make use of the stout improved staggered fermions formulation, with a tree level improved Symanzik gauge action.
Dr
Anthony Francis
(Helmholtz-Institut Mainz)
23/06/2014, 14:35
Talk
We extend our analysis of the leading hadronic contribution to the anomalous magnetic moment of the muon using the mixed representation method to approach the physical point. We present results derived from local-conserved two-point lattice vector correlation functions, computed on a subset of light two-flavor ensembles made available to us through the CLS effort with pion masses as low as...
Mr
Greg McGlynn
(Columbia University)
23/06/2014, 14:55
We determine the scaling behavior of the autocorrelation times of observables constructed from the topological charge density on lattices with periodic and open boundary conditions using a series of high-statistics numerical simulations. The autocorrelation functions of such observables turn out to obey a simple differential equation which allows the motion of topological charge in hybrid...
Dr
Shinsuke M. Nishigaki
(Shimane University)
23/06/2014, 14:55
We evaluate the individual distributions of four smallest eigenvalues from chiral random matrix ensembles interpolating chGSE and chGUE by the quadrature method applied to the Fredholm Pfaffian of dynamical Bessel kernel containing a crossover parameter. These distributions are then fitted with the staggered Dirac spectra of the quenched SU(2) lattice gauge theory in the presence of...
Mr
Thibaut METIVET
(CEA Saclay)
23/06/2014, 14:55
for the BMW Collaboration.
We use 2HEX smeared gauge configurations generated with the Nf=2+1 clover improved Wilson action to investigate pion-pion scattering in the rho channel. The range of lattice spacings (0.054 fm to 0.12 fm) and space-like extents (32 and 48) allows us to extract the scattering parameters through the volume dependence of the effective mass according to Luscher's...
Prof.
Chiho Nonaka
(Nagoya University)
23/06/2014, 14:55
We investigate the structure of the phase diagram of QCD at finite isospin chemical
potential with Wilson fermions.
From the behavior of meson correlators in temporal and spatial directions, Polyakov loop,
isospin density and susceptibilities as a function of isospin chemical potential
at zero and finite temperature, we extract the QCD phases at finite isospin chemical
potential...
Dr
Hideo Matsufuru
(High Energy Accelerator Research Organization (KEK))
23/06/2014, 14:55
We numerically study the SU(2) gauge theory with many flavors.
Dynamical simulation is performed with the standard domain-wall
fermions in fundamental representation at numbers of flavors
Nf=2,4,6, and 8. Nf dependence of the static potential, meson
spectrum, and the eigenvalue spectrum of the Dirac operator
is investigated so as to determine the phase structure.
Dr
Georg Bergner
(ITP Goethe University Frankfurt)
23/06/2014, 14:55
The effective Polyakov loop theory reproduces the main features of the
Yang-Mills theory and QCD at finite temperature. A systematic derivation of the effective theory is a combined strong coupling and hopping parameter expansion. It includes a systematic ordering principle of the effective couplings. I will review this approach as well as results and possible applications.
Furthermore, I...
Ms
Vera Guelpers
(University of Mainz)
23/06/2014, 14:55
Talk
The hadronic vacuum polarization can be determined from the vector
correlator in a mixed time-momentum representation. We explicitly
calculate the disconnected contribution to the vector correlator, both in the $N_f = 2$ theory and with an additional quenched strange quark, using non-perturbatively $O(a)$-improved Wilson fermions. All-to-all propagators are computed using stochastic...
Mr
Tiago Jose Nunes da Silva
(University of Groningen)
23/06/2014, 15:15
We discuss our results on the thermal phase transition in color $SU(3)$ QCD with a large number $N_f$ of fundamental fermions using lattice gauge theory. We study the dependence of the critical temperature $T_c$ of the transition and of the coupling at $T_c$ on $N_f$. These results are used to investigate precursory effects of conformality associated with the emergence of a non-trivial fixed...
Mr
Tadeusz Janowski
(University of Southampton)
23/06/2014, 15:15
I will present preliminary results on K-pi scattering lengths obtained by the RBC-UKQCD
collaboration. The results are obtained using one of our domain wall fermion ensembles with physical quark masses.
I will argue that the large "around-the-world" effects which are present with such light quark masses can be controlled.
Prof.
Lorenz von Smekal
(TU Darmstadt and JLU Giessen)
23/06/2014, 15:15
In G2-QCD the SU(3) gauge group of QCD is replaced by the exceptional Lie group G2. This replacement leads to a theory that does not have a sign problem and can be simulated at finite baryon density using standard lattice techniques. The price to pay is that it contains bosonic as well as fermionic baryons. The physics of the light bosonic baryons is expected to be analogous to other QCD-like...
Mr
Mikhail Denissenya
(University of Graz)
23/06/2014, 15:15
We study the iso-scalar and iso-vector mesons under the exclusion of the low-lying Dirac modes from valence quarks with the overlap operator within the two flavour lattice QCD. We study mesonic correlators and extract states at each level of such low-mode truncation. Our observations support a simultaneous restoration of both SU(2)_L \times SU(2)_R and U(1)_A symmetries. We finally observe...
Mr
Matthias Rottmann
(University of Wuppertal)
23/06/2014, 15:15
The overlap lattice discretization of the Dirac operator preserves the important physical property of chiral symmetry, at the expense of requiring much more effort when solving systems with this operator. We present a preconditioning technique based on another lattice discretization, the Wilson-Dirac operator. Recently, close to normal operators have gained popularity in numerical simulations....
Mr
Tobias Rindlisbacher
(ETH Zurich)
23/06/2014, 15:15
We study QCD with Wilson fermions in the presence of an isospin chemical potential mu_I.
At zero temperature, condensation of iso-positive pions is expected to occur as soon as mu_I reaches half the pion mass.
By looking at the isospin density and the mass spectrum of mesons as a function of mu_I, we investigate this pion condensation on the lattice and extend the study to non-zero...
Ms
Bipasha Chakraborty
(SUPA, School of Physics and Astronomy, University of Glasgow)
23/06/2014, 15:15
Talk
We describe a new technique (presented in arXiv:1403.1778) to determine the contribution to the anomalous magnetic moment (g-2) of the muon coming from the hadronic vacuum polarization using lattice QCD. Our method uses Padé approximants to reconstruct the Adler function from its derivatives at q^2=0. These are obtained simply and accurately from time-moments of the vector current-current...
Dr
Junichi Noaki
(KEK)
23/06/2014, 15:35
We report the status of 2+1-flavor simulations with the Mobius
domain-wall fermions on fine lattices of 1/a = 2.4 and 3.6 GeV.
The violation of the Ginsparg-Wilson relation is controlled at the
level of 0.5 MeV or better. Analyses of the Wilson flow observables,
heavy quark potential and light-hadron correlator are presented.
Mr
Luchang Jin
(Columbia University)
23/06/2014, 15:35
Talk
The anomalous magnetic moment of muon, g-2, is a very precisely
measured quantity. However, the current measurement disgrees with
standard model by about 3σ. Hadronic vaccum polarization and hadronic
light by light are the two types of processes that contribute most to
the theorectial uncertainty. We will discuss the light by light
lattice calculation and some strategies of including QED...
Dr
Bjoern Wellegehausen
(JLU Giessen)
23/06/2014, 15:35
G2-QCD is a QCD-like theory with fermionic baryons and fundamental quarks.
Unlike QCD it does not suffer from a fermion sign problem at finite baryon density and
therefore allows to investigate effects of fermionic baryons on the G2-QCD phase
diagram with standard Monte-Carlo methods.
In the talk we present recent results on the phase diagram at zero and
non-zero temperature with an...
Dr
David Wilson
(Old Dominion University)
23/06/2014, 15:35
We have obtained clear signals of resonances in coupled-channel pi K - eta K scattering. Using distillation and a large basis of operators we are able to extract a precise spectrum of energy levels using the variational method. These energies are analysed using inelastic extensions of the Luescher method to obtain scattering amplitudes that clearly describe S, P and D wave resonances,...
Prof.
Bernd Berg
(Florida State University)
23/06/2014, 15:35
We compare the non-perturbative SU(3) lambada scale of Necco and Sommer with the lambda scale derived by Bazavov et al. from deconfining phase transition data of the Bielefeld group and others. Though the relative discrepancy is never larger than 2%, it matters in some applications. Differences are encountered between results from the set of smaller lattices of Necco and Sommer and ...
Mr
Oscar Akerlund
(ETH Zurich)
23/06/2014, 15:35
We study two exactly solvable conformal models, the critical 2d Ising
model and the
Sommerfield model on the lattice. We find that some conditions on the
geometry of the
lattice must be fulfilled in order to obtain results free of systematic
errors. In the Sommerfield model we also
introduce a mass deformation and measure the mass anomalous dimension,
$\gamma_m$. We find that the...
Dr
Naruhito Ishizuka
(University of Tsukuba)
23/06/2014, 16:30
We presnet our results of the $K\to\pi\pi$ decay amplitudes
for both the $\Delta I=1/2$ and $3/2$ channels.
Calculations are carried out with $N_f=2+1$ gauge configurations
previously generated by the PACS-CS Collaboration
with the Iwasaki gauge action and nonperturbatively
$O(a)$-improved Wilson fermion
at $a=0.091\,{\rm fm}$ and $m_\pi=280\,{\rm MeV}$
on a $32^3\times 64$ ($La=2.9...
Prof.
Ting-Wai Chiu
(National Taiwan University)
23/06/2014, 16:30
We study the charm physics in two-flavors lattice QCD with optimal domain-wall fermion. The gauge ensembles are generated on the $24^3 \times 48 $ lattice with the extent in the fifth dimension $ N_s = 16 $, and the plaquette gauge action at $ \beta = 6.10 $,
for three sea-quark masses corresponding to the pion masses in the range 265-465 MeV. We determine the lattice spacing by the Wilson...
Dr
Piotr Korcyl
(DESY Zeuthen)
23/06/2014, 16:30
We report on the status of large volume simulations with 2+1 dynamical quarks which are being performed by the CLS collaboration. The algorithmic details include: open boundary conditions, twisted mass reweighting and the rational approximation for the strange quark, whereas the main feature of the simulation strategy is the approach to the physical point along a trajectory of constant trace...
Mrs
Ekaterina Mastropas
(College of William and Mary)
23/06/2014, 16:30
Talk
We present a lattice QCD calculation of the ratios of decay constants of the excited states of the pion, to that of the pion ground state. We use an anisotropic clover fermion action with three flavors of quarks, and study the pion decay constants at three values of the light-quark masses, corresponding to pion masses of 391, 524 and 702 MeV. We find that the decay constant of the first...
Masanori Hanada
(Stanford/Kyoto)
23/06/2014, 16:30
In the gauge/gravity duality, the deconfinement transition in the gauge theory is identified with a formation of black hole in the dual gravity theory. In this talk, firstly we give quantitative evidence for this identification from the thermodynamic study of the supersymmetric theory. Then we consider generic gauge theories, including QCD, and show that the deconfinement transition is the...
Dr
Szabolcs Borsanyi
(Bergische Universität Wuppertal)
23/06/2014, 16:30
We present the continuum extrapolated kurtosis, skewness and variance
of the electric charge in a grand canonical ensemble with zero or small chemical
potential. This observable his a particular relevance in Heavy Ion Physics since
ratios of such fluctuations have been measured in experiment at the chemical freeze-out.
We discuss how lattice results describe the STAR fluctuation data at...
Dr
Julius Kuti
(U.C. San Diego)
23/06/2014, 16:30
We will use the minimal composite Higgs model to discuss theoretically and phenomenologically important issues imposed on the low mass near-conformal composite scalar of BSM Higgs physics.
Tereza Mendes
(University of Sao Paulo)
23/06/2014, 16:50
We investigate the critical behavior of electric and magnetic gluon propagators around the deconfinement temperature of SU(2) gauge theory on large lattices, employing Landau gauge. In particular, we study the analytic properties of these propagators using several trial fitting functions.
Dr
Christopher Kelly
(Brookhaven National Laboratory)
23/06/2014, 16:50
The RBC & UKQCD collaborations have recently published lattice results for the K->pi pi decay amplitude in the I=2 channel, A_2, and improved results will be presented at this conference. In this presentation we discuss the determination of the I=0 channel amplitude, A_0. Combining this with A_2 provides epsilon', the measure of direct CP-violation in the Standard Model. In part I we provide...
Mr
chik him wong
(University of California, San Diego)
23/06/2014, 16:50
The widely discussed near-conformal gauge theory with two fermion flavors in the two index symmetric (sextet) representation of the SU(3) color gauge group is the minimal realization of the composite Higgs mechanism. A comprehensive study of flavor singlet scalar spectroscopy with Higgs quantum numbers is reported based on extended new data sets.
Prof.
Heng-Tong DING
(Central China Normal University)
23/06/2014, 16:50
Ratios of cumulants of conserved net charge fluctuations are sensitive to the degrees of freedom that are carriers of the corresponding quantum numbers in different phases of strong interaction matter. We calculate second and fourth order cumulants of net charm and strange fluctuations and their correlations with other conserved charges such as net baryon number and electric...
Prof.
Brian Tiburzi
(City College of New York)
23/06/2014, 16:50
Talk
The Rome method allows one to extract form factors using lattice computations performed strictly at zero momentum. We investigate the size of finite volume effects resulting from this method. As a test case, we focus on the pion charge radius and show how to ascertain the finite volume effect with the aid of chiral perturbation theory. The framework developed can easily be generalized to...
Dr
Christian Schmidt
(Universitaet Bielefeld)
23/06/2014, 17:10
Higher order cumulants of fluctuations of conserved charges are an important diagnostic tool for the thermodynamic properties of strong interacting matter close to freeze out at LHC energies as well as in the entire energy range covered with the beam energy scan (BES) at RHIC.
We present recent progress on the calculation of conserved charge fluctuations with highly improved staggered quarks...
Dr
Alexei Strelchenko
(Fermilab)
23/06/2014, 17:10
Realization of the Incremental eigCG algorithm for solving Hermitian linear systems with multiple right hand sides on the CUDA platform is reported. In particular, we present details of implementation of the algorithm in the QUDA library. Preliminary performance results are provided.
Mr
Daiqian Zhang
(Columbia University)
23/06/2014, 17:10
In continuation of part I, I will discuss our use of all-to-all propagators in order to construct pi-pi operators with reduced coupling to the vacuum, which helps to reduce the noise in the K->pipi(I=0) decay amplitude. I will also present preliminary results for the pipi(I=0) phase shift, decay amplitude A_0, both with physical kinematics. The precise value of A_0, once computed, will provide...
Prof.
Christian Fischer
(JLU Giessen)
23/06/2014, 17:10
I will give an overview on our recent results for the phase
diagram of QCD with Nf=2+1 and Nf=2+1+1 flavors. We use a combination
of lattice and Dyson-Schwinger methods to determine the chiral
and deconfinement order parameters at finite temperature and chemical
potential. We find a critical end-point at large chemical potential
in the vicinity of the chiral critical line extrapolated...
Prof.
Keh-Fei Liu
(University of Kentucky)
23/06/2014, 17:10
We report our calculation of the pi N sigma term and scalar form factor from the overlap fermion on 2+1 flavor domain wall fermion configurations on the 24^3 x 64 lattice at the sea quark mass which
corresponds to the pion mass at 330 MeV. The improvement of the nucleon propagator and the quark loop with low mode average will be discussed.
Dr
Padmanath Madanagopalan
(Institute of Physics, University of Graz)
23/06/2014, 17:10
We present the ground and excited state spectra of triply, doubly and singly-charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational...
Dr
Enrico Rinaldi
(Physics Division, Lawrence Livermore National Laboratory)
23/06/2014, 17:10
Composite Higgs dynamics due to a new gauge sector has recently attracted renewed interest both phenomenologically and on the lattice. In fact, while a scalar particle consistent with the Standard Model Higgs has been discovered at the LHC, the detailed nature of this particle remains unknown. One popular description is that the Higgs is a result of a strongly coupled composite framework, such...
Dr
Justin Foley
(Microway and Nvidia)
23/06/2014, 17:30
We describe recent additions to the QUDA software library that are
aimed at extending strong scaling in multi-GPU lattice calculations.
These include the addition of CPU-thread support in order to increase
concurrency and improve the overlap of computation and communication
in Krylov solver routines, as well as the modifications needed to enable the GPUDirect RDMA feature recently...
Mr
Terukazu Ichihara
(Yukawa Institute for Theoretical Physics and Kyoto University)
23/06/2014, 17:30
We investigate QCD phase diagram at strong coupling based on strong coupling expansion in auxiliary field Monte-Carlo (AFMC) method. The strong coupling expansion is one of the ways to reduce the sign problem since the effective action is described in hadronic degrees of freedom via analytic integration over link variables.
We have found that hadron phase is compressed (extended) at low...
Dr
Daniel Mohler
(Fermilab)
23/06/2014, 17:30
We present results for the mass splittings of low-lying charmonium states from a calculation of Wilson clover quarks with the Fermilab interpretation on an asqtad sea. We use five lattice spacings and two values of the light sea quarks to extrapolate our results to the physical point. Sources of systematic uncertainty in our calculation are discussed and we compare our results for the 1S...
Mr
Junichi Takahashi
(Kyushu University)
23/06/2014, 17:30
We evaluate quark number densities at imaginary chemical potential by doing lattice QCD calculations on an 8^2*16*4 lattice with clover-improved Wilson quarks of two flavors. The quark number densities are extrapolated to the small real chemical potential region by assuming some function forms. The extrapolated quark number densities are consistent with those calculated at real chemical...
Dr
Xu Feng
(Columbia University)
23/06/2014, 17:30
The rare kaon decays, $K \to pi nu nu_bar$ and $K \to pi l^+ l^-$, serve as ideal probes for the observation of New Physics (NP) effects. To isolate the NP contributions successfully, one needs to control the errors for Standard Model prediction from both short- and long-distance contributions.
RBC-UKQCD collaborations have performed a successful exploratory study on the calculation of the...
Mr
Evan Weinberg
(Boston University)
23/06/2014, 17:30
The light Higgs boson of the Standard Model could arise as the consequence of the weakly broken conformal symmetry in a strongly interacting gauge theory just below the conformal window. Here we present a novel idea to study the transition from conformal to confining behavior using an SU(3) gauge theory with four light and eight heavy flavors. This system interpolates between the 12 flavor...
Dr
Nuno Cardoso
(NCSA, University of Illinois)
23/06/2014, 17:50
In this work, we present the GPU implementation of the overrelaxation and steepest descent method with Fourier acceleration methods for Laudau and Coulomb gauge fixing using CUDA for SU(N) with N>2.
A multi-GPU implementation of the overrelaxation method is also presented using MPI and CUDA.
The GPU performance was measured on BlueWaters and compared against the gauge fixing of the CPU MILC code.
Dr
Graham Moir
(University of WUppertal)
23/06/2014, 17:50
We present novel calculations of the mass hierarchy of the $SU(2)$ pure gauge theory on a space-time lattice with an orbifolded fifth dimension. This theory has three parameters; the gauge coupling $\beta$, the anisotropy $\gamma$, which is a measure of the ratio of the lattice spacing in the four dimensions to that in the fifth dimension, and the extent of the extra dimension $N_{5}$. Using a...
Mr
Ziyuan Bai
(Columbia University in the city of New York)
23/06/2014, 17:50
In this work, I used a $32^3 \times 64 \times 32$, 2+1 flavor domain wall
lattice with Iwasaki+DSDR gauge action. The pion mass is 171 MeV and the
kaon mass is 492 MeV. We implement the Glashow-Iliopoulos-Maiani (GIM)
cancellation using charm quark masses of 750 MeV and 592 MeV. This is an
intermediate calculation, in that we are using both a coarse lattice spacing
(1/a = 1.37GeV) so we...
Prof.
Rajiv Gavai
(Tata Institute of Fundamental Research)
23/06/2014, 17:50
Quark number susceptibility on the lattice, obtained by merely adding a \mu N-term with \mu as the chemical potential and N as the conserved quark number, has a quadratic divergence in the cut-off a. We show that it is simply a faithful representation of the corresponding continuum result. While one can eliminate it in the free theory by suitably modifying the action, as is popularly done,...
Mr
Masahiro Ishii
(Kyushu University)
23/06/2014, 17:50
We analyze the pion screening mass calculated with lattice QCD, using the entanglement-PNJL (EPNJL) model. The EPNJL model well reproduces the lattice QCD result. We then predict the sigma meson screening mass with the model. The chiral symmetry restoration can be exhibited by the difference between the pi and sigma meson screening masses. After the chiral symmetry restoration, the two...
Dr
Ari Hietanen
(CP3-Origins, SDU)
23/06/2014, 18:10
We study the meson spectrum of SU(2) gauge theory with two Wilson fermions in the fundamental representation. The theory unifies both Technicolor and composite pseudo Goldstone Boson (pGB) Higgs models of electroweak symmetry breaking. We have calculated the masses of the lightest spin one vector and axial vector mesons. In addition, we have also obtained preliminary results for the mass of...
437.
Conserved currents and results from 2+1f dynamical Mobius DWF simulations at the physical point
Dr
Peter Boyle
(University of Edinburgh)
23/06/2014, 18:10
We discuss the construction of the almost conserved axial and exactly conserved vector currents in the Mobius generalisation of DWF at finite Ls. I then report on the status of 2+1f DWF simulations at the physical point, with a focus on the determinations of the lattice spacings, and of the pion and kaon decay constants and the Kaon bag parameter in the continuum limit.
Mr
Tomomi Sato
(The Graduate University for Advanced Studies)
23/06/2014, 18:10
Motivated by recent arguments on effective restoration of UA(1) symmetry around the critical temperature in two-flavor QCD, we investigate the renormalization group flow of the U(2)xU(2) linear sigma model (LSM) with the traditional epsilon expansion. Introducing the UA(1) violation, the attractive basin falling into the O(4) LSM in the parameter space and its dependence on the size of UA(1)...
Ms
Ruizi Li
(Indiana University)
23/06/2014, 18:10
The conjugate gradient algorithm is among the most essential and time consuming parts of lattice calculations with staggered quarks. We test the performance of dslash, the key step in the CG algorithm, on the Intel Xeon Phi, also known as the many integrated cores (MIC) architecture, with different parallelization strategies using MPI,OpenMP, and the vector processing units (VPUs).
Dr
Wolfgang Unger
(University Frankfurt)
23/06/2014, 18:10
We compare the combinatorics of staggered and Wilson fermions in the strong coupling limit for various colors and flavors. Based on the hopping parameter expansion, we express the partition functions of both discretizations in terms of polynomials with coefficients of distinct combinatorical interpretation.
We address how gauge corrections to the strong coupling limit modify the...
Mr
David Murphy
(Columbia University)
23/06/2014, 18:10
We present an update on the RBC/UKQCD collaboration’s calculation of the kaon semileptonic form factor at zero momentum transfer, $f_{+}^{K \pi}(0)$. This calculation utilizes two new $N_{f} = 2+1$ M\"{o}bius Domain Wall Fermion ensembles which allow us to simulate QCD directly at physical pion mass for the first time. Together with our previous results we now have a complete set of...
Dr
Stephan Durr
(Wuppertal University / Juelich Forschungszentrum)
24/06/2014, 09:45
Talk
Prof.
Andreas Frommer
(University of Wuppertal)
24/06/2014, 10:15
Talk
Dr
Raul Briceno
(JLab)
24/06/2014, 11:15
Talk
Few-body hadronic observables play an essential role in a wide number of processes relevant for both particle and nuclear physics. In order for Lattice QCD to offer insight into the interpretation of few-body states, a theoretical infrastructure must be developed to map Euclidean-time correlation functions to the desired Minkowski-time few-body observables. In this talk, I will first review...
Dr
Pol Vilaseca Mainar
(Instituto Nazionale di FIsica Nucleare)
24/06/2014, 14:15
The chirally rotated Schrödinger functional renders the mechanism of automatic
O(a) improvement compatible with the Schrödinger functional (SF) formulation.
We here report on the determination to 1-loop order in perturbation theory of the
renormalization coefficients necessary to achieve automatic O(a)
improvement and the boundary improvement coefficients needed
to eliminate the extra...
Mr
Maxwell Hansen
(University of Washington)
24/06/2014, 14:15
We calculate matrix elements for beyond-the-Standard-Model contributions to neutral kaon mixing from mixed-action lattice simulations with staggered sea quarks and domain-wall valence quarks. We analyze the (2+1)-flavor MILC asqtad ensembles with multiple light sea-quark masses corresponding to staggered pions as light as 220 MeV on three different lattice spacings a ~ 0.12, 0.09, and 0.06...
Dr
Nigel Cundy
(Seoul National University)
24/06/2014, 14:15
In the past few years, we have presented a new way of considering quark confinement. Through a careful choice of a Cho-Duan-Ge Abelian Decomposition, we can construct the QCD Wilson Loop in terms of an Abelian restricted field. The relationship between the QCD and restricted string tensions is exact; and we do not need to gauge fix, apply any path ordering of gauge links, or additional path...
Dr
Sergey Syritsyn
(RIKEN-BNL Research Center)
24/06/2014, 14:15
I will report initial nucleon structure results computed on lattices with 2+1 dynamical Moebius domain wall fermions at the physical point generated by RBC and UKQCD. At this stage, we evaluate only connected quark contributions. In particular, I will discuss the nucleon electric and magnetic radii, quark contributions to the nucleon spin, the nucleon axial charge, and the quark momentum...
Prof.
Herbert Neuberger
(Rutgers)
24/06/2014, 14:15
The topic of the presentation is the two-point single-eigenvalue distribution correlation function of Polyakov loops in the confined phase of four dimensional SU(N) YM theory at large N.
Prof.
Stephen Sharpe
(University of Washington)
24/06/2014, 14:15
Last year, we presented a generalization of Luescher's two-particle
quantization condition to three identical, degenerate particles.
While completing this work, we discovered a technical problem with our
derivation which invalidated the result, in the sense that not all
finite-volume corrections that fall as powers of the box size were
controlled. We have found
a fix to this problem,...
Mr
Lukas Varnhorst
(Bergische Universität Wuppertal)
24/06/2014, 14:15
We present preliminary results for the determination of the critical
endpoint of the chiral transition in N_f=3 QCD with mu=0 at small N_t.
We have employed an unimproved Wilson gauge action with
staggered fermions, for which previous results on the critical endpoint are available.
As an extension of these results we have studied the dependence of the
critical mass on the strength of the smearing.
Mr
Mattia Dalla Brida
(Trinity College Dublin)
24/06/2014, 14:35
The chirally rotated Schrödinger functional for Wilson quarks allows for finite-volume, mass-independent renormalization schemes compatible with automatic O(a)-improvement. So far, in QCD, the setup has only been studied in the quenched approximation. Here we present first results for Nf=2 dynamical flavors for several renormalization factors of quark bilinears. We discuss how such...
Dr
Andrea Shindler
(Forschungszentrum Jülich)
24/06/2014, 14:35
With the gradient flow, we propose to calculate the QCD component of key
beyond the Standard Model (BSM) matrix elements related to quark and strong theta-CP violations
and the strange scalar content within the nucleon.
The former set of matrix elements impacts our understanding of Electric
Dipole Moments (EDMs) of nucleons and nuclei (a key signature of BSM physics),
while the latter...
Prof.
Ivan Horvath
(University of Kentucky)
24/06/2014, 14:35
We examine the feasibility of the proposition that in Nf=0 QCD there is a temperature range (T_c < T < T_ch) where real Polyakov line (deconfined) vacuum exhibits valence spontaneous chiral symetry breaking and dynamical chiral polarization of Dirac eigenmodes.
Mr
Christian Wiese
(DESY, Zeuthen)
24/06/2014, 14:35
Talk
We report on the ongoing calculations of the European Twisten Mass Collaboration concerning the non-perturbative study of hadron structure. We discuss the status of these computations at the examples of various moments of parton distribution functions and give an update about the calculations for x_g and the full quark PDF of the nucleon.
Mr
Mattia Bruno
(DESY, Zeuthen)
24/06/2014, 14:35
We discuss methods to extract decay constants, meson masses and gluonic observables in the presence of open boundary conditions. Our CLS ensembles have 2+1 flavours of O(a)-improved Wilson fermions and are generated with a small twisted mass as proposed by Luescher and Palombi. We analyse the associated reweighting for different observables.
Liam Keegan
(CERN)
24/06/2014, 14:35
We measure the running of the twisted gradient flow coupling in the Twisted Eguchi-Kawai (TEK) model, the SU(N) gauge theory on a single site lattice with twisted boundary conditions in the large N limit.
Dr
Yoshifumi Nakamura
(RIKEN Advanced Institute for Computational Science)
24/06/2014, 14:35
We present preliminary results on the critical endpoint of
three flavor QCD at zero chemical potential.
We employ the renormalization-group improved Iwasaki gauge action
and $O(a)$-improved Wilson fermion action.
The critical endpoint is determined by using the intersection points
of kurtosis for mixed observable as well as plaquette, gange action density,
Polyakov loop and "chiral...
Nathan Brown
(Washington University in St. Louis)
24/06/2014, 14:55
We present a final analysis of gradient flow and the associated scale $w_0$ measured on the $N_f=2+1+1$ HISQ ensembles. Compared to previously reported results, we have improved the interpolation to physical quark masses using chiral perturbation theory, adjusted for variations in charm quark mass between ensembles, and derived a `prediction' function for estimating the scale using $w_0/a$ on...
Prof.
Edward Shuryak
(Stony Brook)
24/06/2014, 14:55
QCD topology -- mostly instantons -- had been used in the past to explain near-zero Dirac states and chiral symmetry breaking. At $T \sim T_c$ instanton are known to get
decomposed into $N_c$ instanton-dyons. Several lattice observation were naturally
explained by instanton-dyons.
Their partition function is now numerically generated: the statistical ensemble is then used to get spectrum of...
Dr
Mauro Papinutto
(Universita "La Sapienza" and INFN Sez. di Roma)
24/06/2014, 14:55
We present preliminary results of a non-perturbative study of the scale-dependent renormalization constants of a complete basis of Delta F=2 parity-odd four-fermion operators that enter the computation of hadronic B-parameters within the SM and beyond.
We consider non-perturbatively O(a) improved Wilson fermions and our gauge configurations contain two flavors of massless sea quarks.
The...
Prof.
Gunnar Bali
(University of Regensburg)
24/06/2014, 14:55
Talk
We determine singlet and non-singlet hadron structure matrix
elements for the nucleon and the pion from n_f=2 simulations
at the physical quark mass.
Xiao-Yong Jin
(RIKEN Advanced Institute for Computational Science)
24/06/2014, 14:55
We investigate screening masses at finite temperatures with 3 flavors using the non-perturbatively improved clover fermion action and the Iwasaki gauge action. This report focuses on the behavior of the scalar singlet correlator near the thermal critical point. I will explain the technique used to extract the correlator and discuss our preliminary results from ensembles at Nt=8.
Prof.
Antonio Gonzalez-Arroyo
(Instituto de Fisica Teorica UAM/CSIC)
24/06/2014, 14:55
We present the results of our direct precision test of volume
independence for SU(N) Yang-Mills theory on the lattice with
Wilson action. Wilson loop expectation values at large N are
obtained by extrapolation and its finite volume dependence
examined for different boundary conditions.
Dr
Shinji TAKEDA
(Kanazawa University)
24/06/2014, 15:15
We investigate a presence of critical end point in finite density/temperature QCD with three-degenerated Wilson-Clover quarks. The critical end point is estimated by the kurtosis intersection method and a gap of transition points between two independent observables. We also discuss slope/curvature of the critical end line extending from the zero density point whose details will be given in a...
Dr
yibo yang
(University of Kentucky)
24/06/2014, 15:15
Based on the lattice simulation with overlap fermions on 2+1 DWF fermion configurations on the 24^3 x 64 lattice, we carry out the first lattice QCD calculation of the quark and glue contributions to pseudoscalar and vector mesons and the nucleon. The quark mass term contributes about 50% to the mass of the light pseudoscalar mesons; whereas, it is not important in the masses of light vector...
Dr
Jochen Heitger
(University of Muenster)
24/06/2014, 15:15
We present the results of a non-perturbative determination of the improvement coefficient c_A of the axial vector current in three-flavour lattice QCD with O(a) improved Wilson quarks and tree-level Symanzik improved gauge action. Our computation involves an improvement condition which is imposed at a constant physical volume of about 1.2 fm and employs the PCAC relation in the Schrödinger...
Mr
Daniel August
(friedrich schiller universität jena)
24/06/2014, 15:15
The numerical calculation of the fermion determinant is one of the most costly computational tasks in lattice QCD.
For massless two-color QCD in two dimensions we are able to calculate the fermion determinant analytically,
allowing us to obtain high precision results for the mass spectrum of the theory.
In the talk we review our lattice formulation in terms of purely bosonic variables...
Dr
Hana Saito
(DESY Zeuthen)
24/06/2014, 15:15
Tensor network methods form a family of efficient techniques of approximating quantum states. Their successes in quantum many-body physics have inspired their use for lattice gauge theories. We employed one of the tensor network techniques, called Matrix Product States, to investigate the Schwinger model in the Hamiltonian formulation. In this talk, we show our results for the temperature...
Mr
Christian Wittemeier
(Westfälische Wilhelms-Universität Münster)
24/06/2014, 15:35
We report on a non-perturbative computation of the renormalization factor Z_A of the axial vector current in three-flavour O(a) improved lattice QCD with Wilson quarks and tree-level Symanzik improved gauge action. Our normalization condition is formulated at constant physics in the same Schrödinger functional setup as is being used for the determination of the improvement coefficient c_A. It...
Dr
Takumi Iritani
(High Energy Accelerator Research Organization (KEK))
24/06/2014, 15:35
The presence of color source may modify the chiral condensate that characterizes the spontaneous breaking of chiral symmetry in the QCD vacuum. Using the overlap-Dirac eigenmodes, we investigate this phenomenon around static color sources representing quark-antiquark and three-quark systems. We show that the chiral condensate is reduced inside the flux-tube that is formed between the color...
Dr
Ming Gong
(Institute of High Energy Physics, Chinese Academy of Sciences)
24/06/2014, 15:35
The disconnected insertion part of the quark contributions to the nucleon spin are calculated with overlap fermion on DWF configurations. This work is done by calculating the disconnected three point correlation functions through the anomalous Ward identity. The quark loop of the pseudoscalar density is calculated with low-mode average and grid-noise estimate for the high modes. The overlap...
Mr
Ben Galloway
(University of Glasgow)
24/06/2014, 15:35
The system of charmonium has several excited states below the energy threshold for decay into D and Dbar mesons, which can in principle be studied accurately in lattice QCD. Studies that include many states in the spectrum have typically only been done at one value of the lattice spacing and with light quarks in the sea. Here we give results for radial and orbital excitation energies for...
Dr
Balint Toth
(University of Wuppertal)
24/06/2014, 15:35
The finite temperature transition of QCD with three degenerate flavors is expected to become a first order phase transition at small quark masses. It has been observed that introducing a sufficiently large imaginary chemical potential broadens the first order region and raises the critical quark mass to the numerically feasible regime. We report on our search for this first order transition at...
Dr
Stefan Meinel
(Massachusetts Institute of Technology)
24/06/2014, 16:30
Talk
We present results for the disconnected contributions to light-quark nucleon form factors and generalized form factors at a pion mass of approximately 300 MeV. The calculations are performed with clover fermions in a large volume, and the disconnected quark loops are evaluated using the hierarchical probing method. We compare the behavior of hierarchical probing with the traditional noise...
Dr
Yusuke Taniguchi
(University of Tsukuba)
24/06/2014, 16:30
The canonical partition function is related to the grand canonical one
through the fugacity expansion.
In this talk we perform the fugacity expansion by a method of the
hopping parameter expansion in temporal direction: winding number
expansion.
Since the convergence of our expansion is good only for a small
$\kappa$ we concentrate on heavy quark mass region.
For a numerical simulation...
Dr
Martin Schaden
(Rutgers University)
24/06/2014, 16:30
I discuss the discretization of causal space-times on a topological lattice of events with hypercubic coordination whose links are light-like. Conditions that ensure this lattice is the discretization of a causal manifold are derived. They are encoded by a local topological lattice theory which has a particularly simple and appealing form when null-coframes are represented by spinors.
Prof.
Michael Ogilvie
(Washington University)
24/06/2014, 16:30
Recent results applying resurgence theory to finite-temperature field theories yield a detailed analytic structure determined by topological excitations. We examine finite-temperature SU(N) lattice gauge theories in light of these results. Double-trace Polyakov loop deformations move through different regions of the confined phase characterized by continuous change in the adjoint Polyakov...
Robert Mawhinney
(Columbia University)
24/06/2014, 16:30
The RBC and UKQCD Collaborations are generating 2+1+1 flavor Mobius
domain wall fermion configurations with $1/a = 3$ and 4 GeV. To
achieve good topological tunneling at these weaker couplings, the
gauge action is the Wilson action plus a Dislocation Enhancing
Determinant (DED) term. The DED term enhances the probability of
gauge fields where toplogy-changing dislocations are present,...
Dr
Savvas Zafeiropoulos
(LPC Universite Blaise Pascal CNRS)
24/06/2014, 16:30
We summarize recent non-perturbative results obtained for renormalization constants computed in the RI’-MOM scheme for $N_{\rm f}=2+1+1$ twisted mass QCD. Our implementation employs the Iwasaki gauge action and four dynamical degenerate twisted mass fermions. Renormalization constants for scalar, pseudo-scalar, vector and axial operators, as well as for the quark propagator, are computed at...
Mr
Lorenzo Bongiovanni
(Swansea University)
24/06/2014, 16:50
Recently progress has been made in applying complex Langevin dynamics to
nonabelian gauge theories with a sign problem. Here we study the SU(3)
gauge theory with a theta therm and present results at real theta.
Dr
Akihiro Shibata
(KEK)
24/06/2014, 16:50
We have proposed the non-Abelian dual super conductivity in SU(3) Yang-Mills (YM) theory for the mechanism of quark confinement, and by using the proposed gauge link decomposition to extract magnetic monopole in the gauge invariant way we presented the evidences in lattice conferences.
In this talk, we focus on the dual Meissner effects in view of the magnetic monopole in SU(3)...
Dr
Julien Frison
(University of Edinburgh)
24/06/2014, 16:50
While Non-Perturbative Renormalisation by itself can be done at any scale, converting it to a perturbative scheme introduces a systematic error decreasing with the scale. In the case of the B_K four quark operator, this is now the dominant error on the MSbar result at 3 GeV. Increasing this scale requires both the access to finer lattices and a correct treatment of the charm effects. We will...
Dr
Alejandro Vaquero
(The Cyprus Institute)
24/06/2014, 16:50
Talk
We present results for $N_f=2+1+1$ twisted mass fermions on the disconnected contributions to the three point functions entering in studies of hadron structure. Emphasis is given to the nucleon sigma-terms, isoscalar axial charge and first moments of parton distributions for a range of pions masses. The computations are performed using QUDA code implemented on GPUs.
Prof.
Derek Leinweber
(University of Adelaide)
24/06/2014, 16:50
For almost 50 years the structure of the Lambda(1405) resonance has been a mystery for particle physicists. Even though it contains a heavy strange quark and has odd parity its mass is lower than any other excited spin-1/2 baryon. Before the existence of quarks was confirmed, Dalitz and co-workers speculated that it might be a molecular state of an anti-kaon bound to a nucleon. Although the...
Prof.
Ulli Wolff
(Humboldt University, Berlin)
24/06/2014, 16:50
We define a finite size renormalization scheme for
$\phi^4$ theory which in the thermodynamic limit
reduces to the standard scheme used in the
broken phase. We use it to re-investigate
the question of triviality for the four dimensional
infinite bare coupling (Ising) limit. The relevant
observables all rely on two-point functions and
are very suitable for a precise estimation
with the...
Dr
Boram Yoon
(Los Alamos National Laboratory)
24/06/2014, 17:10
Talk
We calculate the disconnected contribution to the nucleon isoscalar charges of the scalar, axial and tensor channels of light quarks. The calculation has been done by using the Clover valence quarks on the MILC N_f=2+1+1 HISQ lattice at a lattice spacing of 0.12 fm and light quark mass corresponding to the pion mass of 310 MeV. Two-point correlators are evaluated from 60 sources distributed in...
Mr
Benjamin Jaeger
(Swansea University)
24/06/2014, 17:10
Simulations with a finite chemical potential typically lead to a severe sign problem, prohibiting any standard Monte Carlo approach. For simulations of QCD we use the complex Langevin method, for which we apply adaptive step-sizes and gauge cooling to ensure the convergence. We present preliminary results for heavy quark QCD and explore the application for two dynamical quarks.
Zhaofeng Liu
(Institute of High Energy Physics)
24/06/2014, 17:10
Two point functions of diquarks are calculated in the Landau gauge on the lattice with overlap fermions on 2+1-flavor domain wall fermion configurations. Masses of diquarks with spin 0 and 1 in the color anti-triplet representation are extracted. Pion mass dependence of the mass difference between the bad and good diquarks are studied.
andre walker-loud
(W&M)
24/06/2014, 17:10
We derive a model-independent expression for finite-volume matrix elements. Specifically, we present a relativistic, non-perturbative analysis of the matrix element of an external current between a one-scalar in-state and a two-scalar out-state. Our result, which is valid for energies below higher-particle inelastic thresholds, generalizes the Lellouch-Luscher formula in two ways: we allow the...
Mr
Jangho Kim
(Seoul National University)
24/06/2014, 17:10
We present matching factors for the four-fermion operators obtained using the non-perturbative renormalization method (NPR) in RI-MOM scheme for improved staggered fermions on the MILC asqtad lattice (N_f = 2+1).
Using 20^3 * 64 lattice (a = 0.12 fm, am_l/am_s = 0.01/0.05), we obtain the matching factor of B_K operator. Also we are in the middle of data analysis on the BSM...
Dr
Masayasu Hasegawa
(Bogoliubov Laboratory of Theoretical Physics, JINR)
24/06/2014, 17:10
Monopoles are considered that play the very important roles for the color confinement mechanism. University of Kanazawa and Pisa groups have shown a number of studies which support the confinement mechanism due to monopole condensations by the lattice simulations.
Instantons that are other topological objects found as solutions of QCD. The close relations to chiral symmetry breaking are...
Dr
Bastian Brandt
(University of Regensburg)
24/06/2014, 17:30
We investigate an alternative lattice discretization of continuum SU(Nc) Yang-Mills theory in which the self-interactions of the gauge field are induced by a path integral over Nc auxiliary bosonic fields which are coupled linearly to the gauge field. In two dimensions there exists an analytic proof that the new discretization reproduces Yang-Mills theory in its non-perturbative continuum...
Mr
Masaaki Tomii
(Graduate university for advanced studies)
24/06/2014, 17:30
We study a non-perturbative determination of the renormalization constants of flavor non-singlet quark bilinear operators. The renormalization condition is imposed on correlation functions of bilinear operators in the coordinate space. The results are converted to the value in the MSbar scheme by a perturbative matching. The calculation is done on gauge configurations generated with the Mobius...
Mr
Dean Howarth
(Rensselaer Polytechnic Institute)
24/06/2014, 17:30
We describe our studies of multi-pion correlation functions computed using stochastic propagators in quenched lattice QCD, harnessing GPUs for acceleration. We find that projecting onto momentum states for the pions becomes enormously expensive and has a poor scaling with the linear extent of the lattice. It is also found that correlations between stochastic propagators appearing in the same...
Dr
Eduardo Follana Adin
(Universidad de Zaragoza)
24/06/2014, 17:30
We investigate numerically the spectral flow introduced by Adams for the staggered Dirac operator on realistic quenched gauge configurations in 2D and 4D. We study both the unimproved and the HISQ Dirac operators, and we compare with the case of spectral flow for Wilson fermions. We show that the spectral flow provides a good topological definition of the index, with a clear separation of high...
Mingyang Sun
(University of Kentucky)
24/06/2014, 17:30
Talk
We present a calculation of $\langle x \rangle$ for the strange quark in the nucleon. We adopt overlap fermion action on 2 + 1 flavor domain-wall fermion configurations on the $24^3 \times 64$ lattice. Smeared grid $Z_3$ sources are deployed to calculate the nucleon two-point function with low-mode substitution. Even-odd grid sources and time-dilution technique with stochastic noises are...
Helvio Vairinhos
(University of Porto)
24/06/2014, 17:30
We integrate out all the link variables in the partition function of SU(N) or U(N) lattice gauge theory with the Wilson plaquette action, for arbitrary values of the lattice coupling. The partition function is recast as a Gaussian integral over auxiliary fields, after using suitable Hubbard-Stratonovich transformations. We extend our formalism to lattice gauge theories with staggered fermions...
Dr
Christian Torrero
(Centre de Physique Théorique (CPT), Aix-Marseille Université)
24/06/2014, 17:50
The nucleon sigma terms are quantities that play a crucial role in phenomenology: among others, they connect the pion-nucleon and the kaon-nucleon amplitudes to the hadron spectrum and they are also relevant for the direct detection of Dark Matter (DM).
We present preliminary results for these sigma terms obtained from N_f=2+1 lattice simulations that are performed at five lattice spacings...
Mr
Yong-Chull Jang
(Seoul National University)
24/06/2014, 17:50
To achieve smaller heavy-quark discretization errors, the OK action was proposed as an improvement of the Fermilab action. The OK action includes the dimension 6 and 7 operators necessary for tree-level matching to QCD through order 1/m_Q^3 for heavy-light mesons and v^6 for quarkonium. To assess the improvement, we extend previous numerical tests with heavy meson masses by analyzing data...
Mr
Boye Buyens
(University Ghent), Dr
Karel Van Acoleyen
(Ghent University)
24/06/2014, 17:50
We consider the matrix product state formalism for the simulation of Hamiltonian lattice gauge theories. To this end, we define matrix product states which are manifestly gauge invariant. As an application, we study 1+1 dimensional one flavor quantum electrodynamics, also known as the massive Schwinger model. We are able to determine very accurately the ground state properties and one-particle...
Prof.
Francesco Knechtli
(University of Wuppertal)
24/06/2014, 17:50
We simulate a theory with two dynamical O(a) improved Wilson quarks
whose mass M is close the charm quark mass and
at three values of the lattice spacing ranging from 0.066 to 0.038 fm.
This theory is a prototype to study the decoupling of heavy quarks.
We measure the mass and cut-off dependence of ratios of gluonic
observables defined from the Wilson flow or the static potential.
The...
Dr
Eruzzi Giovanni
(University of Parma and INFN)
24/06/2014, 17:50
The sign problem prevents lattice simulations of many models of physical interest. One proposal for evading such problems is the thimble regularization. I will discuss its application to the phi^4 0-dimensional integral, which is a toy model that has been studied for many years as a prototype of complex-valued action and raises several problems within a treatment via complex Langevin; this...
Prof.
Thacker H. B.
(University of Virginia)
24/06/2014, 17:50
There is considerable evidence, based on large $N_c$ chiral dynamics, holographic QCD,
and Monte Carlo studies, that the topological structure of the QCD vacuum consists of
discrete quasivacua separated by domain walls across which the local value of
the topological $\theta$ parameter jumps by $\pm2\pi$.
Topological insulators are condensed matter systems which are bulk insulators with...
Dr
Hyung-Jin Kim
(Brookhaven National Laboratory)
24/06/2014, 18:10
The $\eta-\eta'$ mass splitting coming from anomalous effect on U(1) axial currents has been a historical issue.
%
The QCD gauge field topology with instanton can explain this problem and show consistent result with experimental mass of $\eta'$.
%
Based on the $2+1$ flavor lattice QCD simulation, previous $\eta-\eta'$ masses study shows about 15\% level of accuracy.
%
With the advanced...
Valentina Verduci
(University of Graz)
24/06/2014, 18:10
In recent years the study of two particle systems on the lattice has led to excellent results in the meson sector of the QCD spectrum, however baryon resonances remain mostly unexplored.
We present an initial study of pion-nucleon systems as decay product of baryon resonances in different channels. The final goal is to extract the resonance parameters from the correlation functions of...
Mr
Jaehoon Leem
(Seoul National University)
24/06/2014, 18:10
We present results of the Kaon B-parameters calculated using the HYP-improved staggered quarks on the MILC asqtad lattices.
The perturbative matching is done at one-loop level.
We extrapolate the data to physical pion mass using the SU(2) staggered chiral perturbation theory.
After that, we simultaneously extrapolate results to the continuum (a = 0) and physical sea quark mass.
We...
Mr
Alessandro Sciarra
(Goethe University, Frankfurt am Main), Mr
Christopher Pinke
(Institute for Theoretical Physics, Goethe-University Frankfurt am Main)
24/06/2014, 18:10
In recent years it has been shown that Lattice QCD (LQCD) can benefit
enormously from Graphic Processing Units (GPUs), which are well suited
for memory bandwidth limited applications. Accordingly, the usage of
GPUs in LQCD simulations is still expanding,
mainly relying on CUDA, applicable to NVIDIA hardware only. A hardware
vendor independent approach is given by the Open Computing...
Mr
Alessandro Sciarra
(Goethe University, Frankfurt am Main), Mr
Christopher Pinke
(Institute for Theoretical Physics, Goethe-University Frankfurt am Main)
24/06/2014, 18:10
In recent years it has been shown that Lattice QCD (LQCD) can benefit enormously from Graphic Processing Units (GPUs), which are well suited for memory bandwidth limited applications. Accordingly, the usage of GPUs in LQCD simulations is still expanding,
mainly relying on CUDA, applicable to NVIDIA hardware only. A hardware vendor independent approach is given by the Open Computing Language...
Yusuke Namekawa
(University of Tsukuba)
24/06/2014, 18:10
Comparative study of topological charge is performed.
Topological charges are measured by a cloverleaf operator
on smoothed gauge configurations.
Various types of smoothing techniques are employed.
We investigate
to what extent each smoothing makes the topological charge an integer.
Consistency of the topological charge in the fermionic definition
is also examined.
Mr
Alexander Schmidt
(Phd)
24/06/2014, 18:10
We explore two flavor scalar electrodynamics on the lattice, which has a complex phase problem at finite chemical potential. By rewriting the action in terms of dual variables this complex phase problem can be solved exactly. The dual variables are link- and plaquette occupation numbers, subject to local constraints that have to be respected by the Monte Carlo
algorithm. For the simulation we...
Dr
Enrico Rinaldi
(Physics Division, Lawrence Livermore National Laboratory),
Yasumichi Aoki
(Nagoya University)
24/06/2014, 18:10
Poster
The spectrum of twelve-flavor QCD has been studied in details by the LatKMI collaboration. Here we present our updated results obtained with the HISQ action at two lattice spacings, several volumes and fermion masses. We emphasize the existence of a flavor-singlet scalar state parametrically light with respect to the rest of the spectrum, first reported in our paper [1]. This feature is...
Mr
Arjun Gambhir
(College of William and Mary)
24/06/2014, 18:10
Reverse Monte Carlo, by Mak and Sharma, is a technique that allows for stochastic modification of the action of a lattice theory, while respecting the detailed balance condition of the original action. This modification of the action may permit more efficient
evolution of modes with large autocorrelation times. The classic
Swendsen and Wang cluster algorithm for the Ising model is in fact...
Mr
Johannes Heinrich Weber
(Technische Universität München)
24/06/2014, 18:10
The explicit breaking of time-reflection symmetry in the Karsten-Wilczek action is hidden in various mesonic correlation functions that are calculated in the quenched approximation. Two underlying discrete product symmetries are discussed, which each allow for enforcement of time-reflection symmetry for correlation functions constructed according to additional symmetry requirements.
An...
Alessandro Papa
(Universita` della Calabria & INFN-Cosenza)
24/06/2014, 18:10
Three-dimensional Z(N) lattice gauge theories are studied numerically
at finite temperature for N = 5, 6, 8, 12, 13, 20 and for N_t=2,4,8.
For each model the location of phase transitions and their critical
indices are determined. The scaling of critical points with N is proposed.
The data obtained enable us to verify the scaling near the continuum limit
for the Z(N) models at finite temperatures.
Prof.
Weonjong Lee
(Seoul National University)
24/06/2014, 18:10
We present results of $\varepsilon_K$, the indirect CP
violation parameter calculated on the lattice combined with various
inputs from the experiments. In this analysis we use the lattice
results of $B_K$ and $V_{cb}$ for the exclusive channel. In addition,
we also use Wolfenstein parameters from the CKM fitters and UT
fitters. We find 3.4(3) $\sigma$ difference in the exclusive...
Dr
Etsuko Itou
(KEK, Japan)
24/06/2014, 18:10
We show the numerical simulation result for the mass anomalous dimension of the SU(3) gauge theory coupled to Nf = 12 fundamental fermions.
We use both the step scaling method and the hyperscaling for the Dirac eigenmode to determine the anomalous dimension in the vicinity of the infrared fixed point of the theory.
The continuum extrapolation is carefully taken in both analyses.
We also...
Christof Gattringer
(Univ. Graz)
24/06/2014, 18:10
Using hopping expansion techniques we discuss a partial mapping of finite density lattice QCD to dual variables. After truncation the partition sum has only real and positive contributions also at arbitrary chemical potential, and a Monte Carlo simulation is possible. We discuss the algebraic aspects of the dualization and show some first numerical results.
Dr
Eigo Shintani
(Mainz University)
24/06/2014, 18:10
We report preliminary result of all-mode-averaging technique in
Wilson fermion. On two-flavor CLS configurations, we compare the
performance to obtain high precision of nucleon form factor and
hadronic vacuum polarization function using truncated solver with deflated
SAP+GCR algorithm.
Prof.
Attilio Cucchieri
(University of Sao Paulo)
24/06/2014, 18:10
By evaluating the so-called Bose-ghost propagator, we present the
first numerical evidence of BRST-symmetry breaking in minimal Landau
gauge, i.e. due to the restriction of the functional integration to
the first Gribov region in the Gribov-Zwanziger approach. We find
that our data are well described by a simple fitting function, which
can be related to a massive gluon propagator in...
Jack Laiho
(Syracuse University)
24/06/2014, 18:10
Poster
I present the results of a study of Euclidean dynamical triangulations (EDT) in an attempt to formulate a theory of quantum gravity and to make contact with Weinberg's asymptotic safety scenario. There are two unphysical phases appearing in EDT, neither of which resembles semiclassical gravity. When the phase diagram is enlarged by including a nontrivial measure term a new region of the...
Zechariah Gelzer
(University of Iowa)
24/06/2014, 18:10
We are studying the SU(3) gauge theory with 12 staggered fermions, searching for the endpoint of the line of first-order phase transitions in the mass-beta plane. This endpoint plays an important role in our understanding of the phase diagram of this model. Having found this endpoint with high statistics on a small lattice using unimproved staggered fermions, we are working to find it on...
Dr
Konstantin Ottnad
(University of Cyprus)
24/06/2014, 18:10
The extraction of the magnetic form factor of the nucleon at zero momentum transfer is usually performed by adopting a parametrization for its momentum dependence and fitting the results obtained at finite momenta. We present methods that rely on taking the derivative of relevant correlators to extract directly the magnetic form factor at zero momentum without the need to assume a functional...
Mr
Pranjal Vachaspati
(MIT)
24/06/2014, 18:10
In recent work, it has been shown that contractions for multi-nucleon systems can be cast in terms of weighted sums of determinants of matrices constructed from quark propagators. For typical correlation functions even for few nucleon systems, the number of such determinants can be very large depending on the complexity of the interpolating fields that are used. We investigate efficient...
Prof.
Shailesh Chandrasekharan
(Duke University)
24/06/2014, 18:10
Recent developments have shown that the fermion bag approach is a powerful method to solve fermion lattice field theories using Monte Carlo methods. Some sign problems that had remained unsolved earlier can now be solved within this approach. In this work we argue that the fermion bag approach also gives new insight into the mechanism of fermion mass generation. We discuss how chiral...
andre walker-loud
(W&M)
24/06/2014, 18:10
Practitioners of lattice quantum chromodynamics (LQCD) have been some of the primary pioneer users of the state-of-the-art HPC systems, and contribute towards the stress tests of such new machines as soon as they become available. As with all aspects of HPC, I/O is becoming an increasingly specialized component of these systems. In order to take advantage of the latest available...
Swagato Mukherjee
(BNL)
24/06/2014, 18:10
Dr
Thomas Primer
(University of Arizona)
24/06/2014, 18:10
We present calculations of the $K\to\pi,l\nu$ and $D\to\pi,l\nu$ semileptonic form factors at $q^2=0$.
These form factors are important for the determination of the CKM matrix elements $\lvert{V_{us}}\rvert$ and $\lvert{V_{cd}}\rvert$ respectively.
This work uses the HISQ action for both valence quarks and sea quarks on MILC $N_f=2+1+1$ configurations.
We employ twisted boundary conditions...
Dr
Siwei Qiu
(National Institute of Health)
24/06/2014, 18:10
Neurophysics is a relatively new science. We will use quantum field theory to analyze the neural network of theta model. With a special lattice, one can explore the short term memory using lattice field theory calculation. Here we will theoretically show the path integral formalism which can be used to do perturbation theory. Simple lattice simulation will be conducted to compare with the...
Dr
Marcus Petschlies
(Cyprus Institute / CaSToRC)
24/06/2014, 18:10
We present our results for the electron, the muon, and the tau anomalous magnetic moments obtained with four dynamical quarks.
Performing the continuum limit and an analysis of systematic effects, full agreement with phenomenological results is seen.
Additionally, the light quark contributions on the four-flavour sea are compared to the values obtained for N_f=2
physically light quarks. In...
Dr
Frank Winter
(Thomas Jefferson National Accelerator Facility)
24/06/2014, 18:10
The Low Level Virtual Machine (LLVM) compiler infrastructure is a
promising platform for development of code that features performance
portability across a wide variety of architectures. It's widely
embraced by HPC industry and academia and high performance code
generating backends are available and supported for many relevant
architectures such as CUDA, X86-64, PowerPC64 including...
Mr
Sourav Mondal
(Indian Association for the Cultivation of Science)
24/06/2014, 18:10
Following the multilevel scheme we present an error reduction algorithm for extracting glueball masses from monte-carlo simulations of pure SU(3)
lattice gauge theory. We look at the two lightest states viz. the 0^{++}
and 2^{++}. Our method involves looking at correlations between large wilson loops and does not require any smearing of links. The error bars we obtain are at the moment...
Prof.
Christine Davies
(University of Glasgow)
24/06/2014, 18:10
HPQCD Collaboration: We will present the first lattice QCD calculation of the mixing parameters f_B\sqrt(B_B) and f_B_s\sqrt(B_B_s) for physical light quark masses. We use 2+1+1 MILC configurations at 3 values of the lattice spacing and with three u/d quark masses going down to the physical value. We use improved NRQCD for the b quarks.
Michael Wagman
(University of Washington)
24/06/2014, 18:10
Neutron-antineutron oscillation is a baryon number violating process that is predicted to occur in many theories of physics beyond the standard model. To make quantitative predictions that can be compared to experiment, matrix elements of six-quark effective operators must be computed via lattice QCD and must also be connected to continuum beyond the standard model operators. We present...
Dr
Alexander Rothkopf
(Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany), Dr
Peter Petreczky
(Brookhaven National Laboratory - Department of Physics, Upton, USA)
24/06/2014, 18:10
We present the results of a recent study on the in-medium modification of the spectral properties of Bottomonium S-wave (\Upsilon) and P-wave (\chi_b) states. The medium degrees of freedom are represented by 48^3x12 HotQCD lattices with Nf=2+1 light HISQ flavors, which span the temperature range 140.40(MeV)(= 0.911T_C) < T < 248.63(MeV)(= 1.614T_C). The heavy quarks on the other hand are...
Dr
Piotr Korcyl
(DESY Zeuthen)
24/06/2014, 18:10
We report on our non-perturbative investigations of Supersymmetric Yang-Mills Quantum Mechanics with four supercharges. We employed two independent numerical methods. As a first method we used the cut Fock space approach in which one constructs the Hamiltonian matrix in an approximated basis of the Hilbert space and diagonalize it numerically to obtain the energy spectrum. As a second method...
Mr
Jeonghwan Pak
(Seoul National University)
24/06/2014, 18:10
There are new NVIDIA technologies, such as direct parallelism and GPU Direct, which reduce the communication time between GPUs and CPUs. NVIDIA Kepler GPUs also provide new features to improve the memory usage of CUDA codes which allows better performance in memory access, memory allocation, and deallocation. We optimize our conjugate gradient code for staggered quarks to obtain the full...
Dr
Markus Pak
(University of Graz)
24/06/2014, 18:10
The chirally symmetric Overlap quark propagator is explored for the first time in Coulomb gauge. This gauge is well suited for studying the relation between confinement and chiral symmetry breaking. The dressing functions of the quark propagator and the dynamical mass function are evaluated. Chiral symmetry is then artificially restored by removing the low eigenmodes from the Dirac operator....
Dr
Michael Creutz
(Physics Department, BNL)
24/06/2014, 18:10
Partially quenched chiral perturbation theory usually assumes that
valence quarks propagating on gauge configurations prepared with sea
quarks of different masses will form a chiral condensate as the
valence quark mass goes to zero. I present a counterexample involving
non-degenerate sea quarks where the valence condensate does not form.
Mr
Marios Costa
(University of Cyprus)
24/06/2014, 18:10
The chromomagnetic operator mixes with a large number of operators under renormalization. We identify which operators can mix with the chromomagnetic operator, at the quantum level. Even in dimensional regularization (DR), which has the simplest mixing pattern, the chromomagnetic operator mixes with a total of 9 other operators,forming a basis of dimension-five (d=5), Lorentz scalar operators...
Mr
Alessandro Amato
(Swansea University)
24/06/2014, 18:10
The properties of the ground state of two-color QCD at non-zero baryon chemical potential mu present an interesting problem in strongly-interacting gauge theory; in particular the nature of the physically-relevant degrees of freedom in the superfluid phase
in the high-mu regime still needs clarification. In this study we present evidence for in-medium effects at high mu by studying the wave...
Dr
Shinji Ejiri
(Niigata University)
24/06/2014, 18:10
We investigate the phase transitions of (2+Nf)-flavor QCD, where two light flavors and Nf massive flavors exist, to discuss the electroweak baryogenesis in realistic technicolor scenario. Because an appearance of a first order phase transition at finite temperature is a necessary condition for the baryogenesis, it is important to study the nature of phase transition in the case of massless 2...
Dr
Christopher Monahan
(College of William and Mary),
Kostas Orginos
(College of William and Mary / JLab)
24/06/2014, 18:10
Lattice QCD calculations of parton distribution functions have so far been restricted
to only their first few Melin moments. Broken rotational symmetry on the lattice introduces unavoidable power divergent mixing of lattice twist-2 matrix elements of different spin that obscures the continuum limit. Here I discuss new options that either avoid power divergent mixing or allow us to perform...
Ms
Olga Larina
(Institute of Theoretical and Experimental Physics)
24/06/2014, 18:10
We calculated correlators of vector and pseudoscalar currents in external strong abelian magnetic field in SU(3) gluodynamics.
The masses of charged and neutral mesons with various spins were calculated. We found out that the masses of mesons with zero spin s=0 decreased in increasing magnetic field, but the masses of Rho mesons with nonzero spin increased in the field.
Mr
Thomas Kloiber
(University of Graz)
24/06/2014, 18:10
We study the effect of the theta angle in two dimensional scalar QED. Since the theta term is purely imaginary, it introduces a complex action problem which prevents conventional numerical simulations at non-zero values of theta. This problem is solved by mapping the model to a dual representation, which is real and non-negative, hence suitable for Monte Carlo simulations. We present technical...
Oliver Witzel
(Boston University)
24/06/2014, 18:10
In order to study the transition from conformal to confining behavior of an SU(3) gauge theory, we present the novel idea to simulate a theory with four light and eight heavy flavors. Varying the mass of the heavy flavors, the theory changes from conformal to confining allowing us to demonstrate the walking nature of the running coupling as a function of the mass of the eight heavier flavors.
Dr
Matthew Wingate
(DAMTP, University of Cambridge)
24/06/2014, 18:10
This poster reviews our recent calculation of $B \to K^*$, $B_s \to \phi$, and
$B_s \to K^*$ form factors using nonrelativistic heavy quarks and improved
staggered quarks on MILC lattices. These unquenched calculations, performed
in the low-recoil kinematic regime, provide a significant improvement over the
use of extrapolated light cone sum rule results. We use the form factors
along...
Dr
Ydalia Delgado Mercado
(University of Graz)
24/06/2014, 18:10
We use the density of states method to compute the observables of the effective center model of QCD at finite density (where the system suffers from a complex phase problem). The density of states method is a reweighting method based on an improved evaluation of histograms for the distribution of states. We test this approach against the results from the dual simulations of the model, where...
Prof.
Carleton DeTar
(University of Utah)
24/06/2014, 18:10
We present preliminary simulation results for the I = 0 charmonium state X(3872)(1++) and the I = 1 charmonium state Zc(3900)(1+-). The study is performed on (2+1+1)-flavor highly improved staggered quark (HISQ) lattices with clover (Fermilab interpretation) charm quarks and HISQ light quarks. Since the X(3872) lies very close to the open charm D-bar-D* threshold, we use a combination of...
Alexei Bazavov
(University of California/University of Iowa)
24/06/2014, 18:10
We study the U(1)-Higgs model in two dimensions in the strongly coupled regime. The goal is to generate an effective theory where link variables are integrated out, producing 4-field operators. This theory can be matched with the second-order perturbation theory effective Hamiltonian for the Bose-Hubbard model. Such correspondence can then be exploited for building a lattice gauge theory...
Prof.
Gernot Münster
(University of Muenster)
24/06/2014, 18:10
In Monte Carlo simulations of $\mathcal{N}=1$ supersymmetric Yang-Mills theory the mass of the unphysical adjoint pion, which is easily obtained numerically, is being used for the tuning to the limit of vanishing gluino mass. We show how to define the adjoint pion in the framework of partially quenched chiral perturbation theory and we derive a relation between its mass and the mass of the...
Ion-Olimpiu Stamatescu
(Inst. Theor. Physik, Universitaet Heidelberg)
24/06/2014, 18:10
We use the heavy dense approximation of QCD (HD-QCD) at
next-to-leading order (NLO) in the hopping expansion, keeping the
full Yang-Mills action. We perform simulations at low temperatures,
in the region below 1/3 T_c(\mu=0), and at large \mu, \mu/T above 5.
We analyse the structure in the baryonic density and other quantities
at the onset. We present data from reweighting (RW) and...
Dr
Björn Leder
(University of Wuppertal)
24/06/2014, 18:10
Quark mass reweighting can be used to tune the mass of dynamical quarks. The basic idea is to use gauge field ensembles generated at some bare mass parameters to evaluate observables at different bare sea quark masses. This involves the computation of so called reweighing factors which are given as ratios of fermion determinants. In the case of simulations including the strange quark,...
Prof.
Anna Hasenfratz
(University of Colorado Boulder)
25/06/2014, 09:00
The gradient flow renormalized coupling offers a relatively inexpensive way to calculate the step scaling function or the lattice scale, but both applications can be hindered by large lattice artifacts. Recently we introduced an empirical non-perturbative improvement that can remove O(a^2) lattice artifacts. The method is easy to implement and can be applied to any lattice gauge...
Dr
Waseem Kamleh
(University of Adelaide)
25/06/2014, 09:00
The role of 5-quark operators in extracting the nucleon excited state spectrum via correlation matrix techniques is explored. In particular, the coupling of meson-baryon operators to nucleon resonance states and scattering states is studied. Results are presented for 2+1 flavour dynamical ensembles in both the positive and negative parity channels.
Dr
michele caselle
(Department of Physics, Torino University)
25/06/2014, 09:00
One of the most interesting recent results on the effective string description of Lattice Gauge Theories is the universality of the first few terms of the effective action. This is a direct consequence of the Lorentz invariance of the underlying LGTs and makes this theory much more predictive than usual effective models in particle physics.
Besides the well known Nambu-Goto action, one of...
Dr
Indrakshi Raychowdhury
(Institute of Mathematical Sciences, Chennai, India)
25/06/2014, 09:00
Within the Hamiltonian formulation of Lattice gauge theories, prepotentials, belonging to the fundamental representation of the gauge group and defined locally at each site of the lattice, enables us to construct local loop operators and loop states. Within this prepotential approach one gets mass gap analytically in some approximations in the weak coupling limit of the theory.
Prof.
Jacobus Verbaarschot
(Stony Brook University)
25/06/2014, 09:00
In a sector of fixed topological charge, the chiral condensate has a discontinuty given by the Banks-Casher formula also in the case of one-flavor QCD. However, at fixed $\theta$ angle, the chiral condensate remains constant when the quark mass crosses zero. To reconcile these contradictory observations, we have evaluated the spectral density of one-flavor QCD at $\theta=0$. For negative...
Mr
Antoine Gérardin
(LPT)
25/06/2014, 09:00
I will present results on the scalar B meson ($B_0^*$) sector using $N_f=2$ $\mathcal{O}(a)$-improved Wilson-Clover fermions and the Heavy Quark Effective Field theory at the static limit to describe the b-quark. Since the scalar B meson lies near the B $\pi$ threshold for our simulations set-up, we have implemented meson-meson as well as quark-antiquarks interpolating fields to disentangle...
Dr
Tomomi Ishikawa
(RIKEN BNL Research Center)
25/06/2014, 09:20
Neutral B meson mixing matrix elements and B meson decay constants are calculated. Static approximation is used for b quark and domain-wall fermion is employed for light quarks. The calculations are carried out on Nf=2+1 dynamical ensembles with lattice spacings of 0.086fm and 0.11fm, and a fixed physical spatial volume of about (2.7fm)^3, generated by RBC/UKQCD Collaborations. We employ two...
Dr
Georg Engel
(Universita' Milano-Bicocca)
25/06/2014, 09:20
Exploiting the Banks-Casher relation, we present a direct determination of the chiral condensate in two-flavor QCD, computing the mode number of the O(a)-improved Wilson-Dirac operator below various cutoffs. We make use of CLS-configurations with three different lattice spacings in the range of 0.05-0.08 fm and pion masses down to 190 MeV. Our data indicates a finite density of eigenmodes near...
Mr
Davide Vadacchino
(Università degli Studi di Torino - INFN Sezione di Torino)
25/06/2014, 09:20
The U(1) lattice gauge theory in three dimensions is a perfect laboratory to study the subtle properties of the confining string. On the one hand, thanks to the mapping to a coulomb gas of monopoles, the model can be exactly solved and confinement proven analytically. On the other hand high-precision numerical estimates of Polyakov loop correlators can be obtained via a duality map to a spin...
Mr
Akio Tomiya
(Osaka University)
25/06/2014, 09:20
We investigate the issue of possible restoration of the axial U(1)
symmetry at finite temperature, using lattice simulations with the
Mobius domain-wall fermion. In this talk, we focus on the effects of
near-zero Dirac eigenmodes, which play a crucial role for both
SU(2)xSU(2) chiral symmetry restoration and the restoration/breaking
of axial U(1) symmetry.
Performing simulations at two...
Mr
Marcin Szyniszewski
(Lancaster University, The University of Manchester)
25/06/2014, 09:20
We employ exact diagonalization with strong coupling expansion to the massless and massive Schwinger model. For the massless case, this allows us for a high accuracy continuum limit estimation of the ground state energy and scalar and vector mass gaps with precisions of the order of one part per billion or better.
Furthermore, we investigate the chiral condensate and compare our calculations...
Wolfgang Soeldner
(Regensburg University)
25/06/2014, 09:20
Based on CLS simulations with 2+1 flavors and open boundaries we present first results of the baryon spectrum. We report on the status of our effort related to these simulations and the chiral extrapolation to the physical point.
Dr
Jarno Rantaharju
(Riken Advanced Institute for Computational Science)
25/06/2014, 09:20
We present preliminary results of the gradient flow running coupling with Dirichlet boundary condition in the SU(2) gauge theory with 8 fermion flavors. Improvements to the gradient flow measurement allow us to obtain a robust continuum limit. The results are consistent with perturbative running in the weak coupling region and show slow running at strong coupling.
Oliver Witzel
(Boston University)
25/06/2014, 09:40
We compute B-meson decay-constants and neutral B-meson mixing using relativistic b-quarks and domain-wall light quarks. We present results for fB, fBs, and their ratio including a complete systematic error budget from an analysis of five sea-quark ensembles with pion masses as light as ~290 MeV and two lattice spacings of a~0.11 and 0.08 fm. We are currently adding data at the physical pion...
Mr
Christos Kallidonis
(The Cyprus Institute)
25/06/2014, 09:40
We present results on the masses of the low lying baryons using gauge configurations with $N_f=2+1+1$ flavors of maximally twisted mass fermions. The strange and charm quark masses are tuned to their physical values. We use three values of the lattice spacing, determined from the nucleon mass. Both cut-off effects and volume effects are investigated. We demonstrate that isospin symmetry...
Prof.
Tamas G. Kovacs
(Institute for Nuclear Research, Debrecen)
25/06/2014, 09:40
Recently we found an Anderson-type localization-delocalization transition in the QCD Dirac spectrum at high temperature. Using spectral statistics we obtained a critical exponent compatible with that of the corresponding Anderson model. Here we study the spatial structure of the eigenmodes both in the localized and the transition region. Based on previous studies in the Anderson model, at the...
Francesca Cuteri
(Università della Calabria, INFN-Cosenza)
25/06/2014, 09:40
The transverse profile of the chromoelectric field generated by a quark-antiquark pair in the SU(3) vacuum is analysed within the dual superconductor scenario, then the London penetration depth and coherence length are extracted.
The color field is determined on the lattice through a connected correlator of two Polyakov loops measured on smeared configurations.
Prof.
C.-J. David Lin
(National Chiao-Tung University, Taiwan)
25/06/2014, 09:40
We present our study of the running coupling constant in SU(3) gauge theory with 12 flavours of fermions. In this work we use the method of the step scaling, implemented on lattices with twisted boundary condition. The lattice volumes in this work are 6, 8, 10, 12, 16, 20, and 24. This choice of volumes enables us to investigate the systematic effects in the continuum extrapolation. We...
Dr
Elena Garcia Ramos
(HU Berlin / DESY-Zeuthen)
25/06/2014, 09:40
We present our results for the topological susceptibility in the quenched case and attempt a non-perturbative test on the Witten-Veneziano formula. We perform a continuum limit extrapolation of the topological susceptibility computed using spectral projectors.
The physical situation of the quenched ensembles was matched to the maximally twisted mass dynamical simulations used to compute the...
David Adams
(Nanyang Technological University)
25/06/2014, 09:40
An update on our ongoing research on staggered Wilson fermions (a 2-flavor staggered version of Wilson fermions) will be given. Previously we found that this formulation is 4-6 times more efficient than usual Wilson fermions for inverting the Dirac matrix in quenched backgrounds of a 16^3 x 32 lattice at beta=6. Further results for 20^3 x 40 lattices will be reported which reveal that the...
Mr
Francesco Negro
(INFN - Sezione di Pisa)
25/06/2014, 10:00
We determine the static quark anti-quark potential for QCD at the
physical point in the presence of an external magnetic field.
The potential is anisotropic, in particular it is steeper in the
directions orthogonal to the magnetic field than in the parallel one.
The string tension increases (decreases) in the orthogonal
(parallel) directions; the absolute value of the Coulomb...
Dr
Krzysztof Cichy
(DESY Zeuthen)
25/06/2014, 10:00
We present a comparison of different definitions of the topological charge on the lattice, with 2 and 2+1+1 flavours of dynamical twisted mass fermions. We give detailed results at one lattice spacing and also show that the correlation between different definitions increases as one approaches the continuum limit. The investigated definitions are: index of the overlap Dirac operator, spectral...
Prof.
Colin Morningstar
(Carnegie Mellon University)
25/06/2014, 10:00
The spectrum of excited isovector mesons is studied using a 32^3 x 256 anisotropic lattice with u,d quark masses set to give a pion mass near 240 MeV. Results in the bosonic isovector nonstrange symmetry channels of zero total momentum are presented using correlation matrices of unprecedented size. In addition to spatially-extended single meson operators, large numbers of two-meson operators...
Prof.
Luigi Del Debbio
(University of Edinburgh)
25/06/2014, 10:00
The four-fermi interaction can play an important role in models of
strong dynamical EW symmetry breaking if the anomalous dimension of
the four-fermi operators becomes large in the IR.
The anomalous dimension can be computed nonperturbatively using a
Schroedinger functional formalism. We present a computation
of the four-fermi anomalous dimension for the SU(2) gauge theory with
two...
Aida El-Khadra
(University of Illinois)
25/06/2014, 10:00
We present the status of our calculation of the hadronic matrix elements for neutral B-meson mixing with asqtad sea and valence light quarks and using the Wilson clover action with the Fermilab interpretation for the b quark. We calculate the matrix elements of all five local operators that contribute to neutral B-meson mixing both in and beyond the SM. Our analysis includes MILC asqtad...
Prof.
Sinya Aoki
(Kyoto University)
25/06/2014, 10:00
We investigate some aspects of 2-flavor QCD with $m_u¥not= m_d$ at low-energy, using the leading order chiral perturbation theory including anomaly effects. While nothing special happens at $m_u=0$ for the fixed $m_d¥not=0$, the neutral pion mass becomes zero at two critical values of $m_u$, between which the neutral pion field
condenses, leading to a spontaneously CP broken phase, the...
Dr
Matteo Giordano
(Institute for Nuclear Research (ATOMKI), Debrecen)
25/06/2014, 10:00
Above the QCD chiral crossover temperature, the low-lying eigenmodes of the Dirac operator are localised, while moving up in the spectrum states become extended. This localisation/delocalisation transition has been shown to be a genuine second-order phase transition, in the same universality class as that of the 3D Anderson model. The existence of localised modes and the effective dimensional...
David Richards
(Jefferson Laboratory)
25/06/2014, 10:20
We present an investigation of the excited meson spectrum at the N_f= 3 point obtained on isotropic clover lattices with a plaquette Wilson gauge action, and a NP-improved clover fermion action, at a lattice spacing of a \simeq 0.08 fm, and compare with corresponding calculations on an anisotropic lattice at fine temporal lattice spacing but a spatial lattice spacing of a_s \simeq 0.125 fm. ...
Dr
Joyce Myers
(Niels Bohr Institute)
25/06/2014, 10:20
We develop a diagrammatic approach for calculating the chiral condensate on the lattice at strong coupling for QCD and related theories with fermions in the symmetric, antisymmetric, and adjoint representations. The approach is inspired by recent work of Tomboulis and earlier work in which the chiral condensate is obtained diagrammatically in the limit of infinite coupling. We calculate the...
Dr
Tung-Han Hsieh
(Academia Sinica)
25/06/2014, 10:20
We study the chiral properties of the pseudoscalar meson in 2-flavors lattice QCD with optimal domain-wall fermion. The gauge ensembles are generated on the $ 24^3 \times 48 $ lattice with the extent in the fifth dimension $ N_s = 16 $, and the plaquette gauge action at $ \beta = 6.10 $, for three sea-quark masses corresponding to the pion masses in the range 265-465 MeV. We calculate the mass...
Dr
Ferenc Pittler
(Eotvos Lorand University)
25/06/2014, 10:20
At low temperature the low-lying QCD Dirac spectrum obeys random matrix statistics. Recently we found that above $T_{c}$ the lowest part of the spectrum consists of localized modes that obey Poisson statistics. An interesting implication of this is that as the system crosses $T_{c}$ from above, the spectral statistics at $\lambda=0$ changes from Poisson to random matrix. Here we study this...
Mr
Christian Zielinski
(Nanyang Technological University, Division of Mathematical Sciences)
25/06/2014, 10:20
Results for the spectrum of the staggered Wilson Dirac operator in quenched backgrounds (beta = 5.8 and 6) are presented for a range of different lattice sizes up to 16^3 x 32. Significant improvement in the physical branch of the spectrum is observed for the larger lattices. The results are also compared with spectrum results for the usual Wilson Dirac operator in the same backgrounds.
Dr
Yoshiaki Koma
(Numazu College of Technology)
25/06/2014, 10:20
We study the static three-quark potential in SU(3) lattice gauge theory at zero temperature with the Polyakov loop correlation function (PLCF) consisting of three Polyakov loops.
Compared to the use of the three-quark Wilson loop, the PLCF allows us to investigate
the ground state potential of various three-quark configurations in detail with less systematic effects.
We overcome the problem...
Mr
Justus Tobias Tsang
(University of Southampton)
25/06/2014, 11:10
We study the feasibility of using a novel discretisation (Moebius) to directly simulate charm physics within the Domain Wall formalism. We then present results for a range of physical quantities including meson masses as well as decay constants and the dispersion relation of heavy-heavy (eta_c) and heavy-strange (D_s) pseudoscalar mesons. Four extensive sets of tree-level Symanzik pure gauge...
Mr
Atsuro Ikeda
(Osaka University)
25/06/2014, 11:10
We study the charmonium property at finite temperature and finite momentum in
quenched lattice QCD with improved maximum entropy method (MEM).
We extend the MEM analysis to the product space of the correlation functions at more
than two different momenta to take advantage of more data and the strong
correlation among Euclidean correlators with different momenta.
We find that this method...
Mr
Masayuki Wakayama
(Nagoya University)
25/06/2014, 11:10
Our purpose is to obtain insights of structure of the sigma meson from lattice QCD. At present we do not reach a conclusive understanding of nature of the sigma meson. Currently it is considered as a usual two-quark state, four-quark states such as a tetra-quark and mesonic molecules or superposition of them. At present we do not reach a conclusive understanding of nature of the sigma meson....
Dr
Richard Brower
(Boston University)
25/06/2014, 11:10
Lattice radial quantization is a nonperturbative method especially suited to numerically solve Euclidean conformal field theories.
Tests are made for the critical surface of the
phi 4th theory at the Wilson-Fisher critical point
in 3D on R x S2 and in 2D on the Riemann sphere.
Simplicial lattice using the Finite Element Methods (FEM) or Regge calculus discretization are need to...
Mr
Stefano Piemonte
(WWU Münster)
25/06/2014, 11:10
The behaviour of supersymmetric theories at finite temperatures differs from that of other theories in certain aspects. Due to the different thermal statistics of bosons and fermions, supersymmetry is explicitly broken for any non-zero value of the temperature. We study the N=1 supersymmetric Yang-Mills theory on the lattice at finite temperatures. This model is the simplest supersymmetric...
Dr
Georg von Hippel
(University of Mainz)
25/06/2014, 11:10
Talk
We study the ability of a variety of fitting techniques to extract the ground state matrix elements of the vector current from ratios of nucleon three- and two-point functions that contain contaminations from excited states. Extending our high-statistics study of nucleon form factors, we are able to demonstrate that the treatment of excited state contributions in conjunction with approaching...
Marco Cè
(Scuola Normale Superiore, Pisa, Italy and INFN, Sezione di Pisa, Italy)
25/06/2014, 11:10
We present a precise computation of the topological charge distribution in the SU(3) Yang–Mills theory. It is carried out on the lattice with high statistics Monte Carlo simulations by employing the clover discretization of the field strength tensor combined with the Yang–Mills gradient flow. The flow equations are integrated numerically by a fourth-order structure-preserving Runge–Kutta...
Yannick Meurice
(University of Iowa)
25/06/2014, 11:30
The idea of blocking in configuration space has played an important role in the development of the RG ideas. However, despite
being half a century old and having had a huge intellectual impact, generic numerical methods to perform blocking for lattice models have progressed more slowly than sampling methods. Blocking may be essential to deal with near conformal situations. Typically,...
Dr
Andreas Juettner
(University of Southampton)
25/06/2014, 11:30
This talk will provide an overview of RBC/UKQCD's charm project on their
2+1 flavour physical point ensembles using Moebius Domain Wall Fermions
for the light as well as for the charm quark. After a brief motivation
of DWF as a suitable heavy quark discretisation we will show first
results for masses and matrix elements.
Joshua Berlin
(University of Frankfurt)
25/06/2014, 11:30
The structure of the light-scalar meson a_0(980) is under debate. It might be of quark-antiquark, diquark-antidiquark or mesonic molecule type. We have implemented corresponding interpolating field operators composed of two and of four quarks, as well as operators of two-meson type, to study the structure of a_0(980). The computation of the correlation matrix is rather challenging, because of...
Dr
ANOSH JOSEPH
(Deutsches Elektronen-Synchrotron DESY)
25/06/2014, 11:30
Certain classes of supersymmetric gauge theories, including the well known N=4 super Yang-Mills (SYM) theory, that takes part in the AdS/CFT correspondence, can be formulated on a Euclidean spacetime lattice using the techniques of exact lattice supersymmetry. Great ideas such as topological twisting, Dirac-Kahler fermions, geometric discretization all come together to create gauge theories...
Mr
Florian Meyer
(University of Bielefeld, Germany)
25/06/2014, 11:30
We present new results on the reconstruction of mesonic spectral functions for
three temperatures above T_c in quenched QCD. Making use of Clover improved
Wilson valence quarks allows for a clean extrapolation of correlator data to
the continuum. For the case of vanishing momentum the spectral function is
obtained by fitting the data to a well motivated ansatz. In the vector channel
for...
Dr
Giannis Koutsou
(The Cyprus Institute)
25/06/2014, 11:30
Talk
The electromagnetic form factors of the nucleon using twisted mass fermion configurations simulated by the ETM collaboration are presented. These include a gauge field ensemble simulated with two degenerate light quarks yielding a pion mass of around 130 MeV, as well as two ensembles yielding pion masses of 210 MeV and 370 MeV with additional strange and charm sea quarks tuned to their...
Dr
Andre Sternbeck
(University of Regensburg)
25/06/2014, 11:30
We investigate the exact gluonic Dyson-Schwinger equation of quenched SU(n) lattice gauge theory in Landau gauge and the lattice analog of the
Kugo-Ojima confinement criterion.
Dr
Abdou Abdel-Rehim
(The Cyprus Institute)
25/06/2014, 11:50
We carry out a study of the light scalar meson a_0(980) employing
interpolating field operators of quark-antiquark, diquark-antidiquark,
mesonic molecules and two-particle meson operators. Both connected and
disconnected quark loops are investigated. We present preliminary results
for two ensembles of 2+1 clover fermion gauge configurations generated
by the PACS-CS collaboration...
Urs Wenger
(University of Bern)
25/06/2014, 11:50
The conjectured holographic duality between supersymmetric Yang-Mills
quantum mechanics and type IIa string theory in principle allows to
probe the physics of certain supergravity black holes by lattice Monte
Carlo simulations. In this talk we derive the fermion loop formulation
of the 4 and 16 supercharge SU(N) theory on the lattice. The loop
formulation naturally separates the...
Mr
Yong-Gwi Cho
(University of tsukuba)
25/06/2014, 11:50
We present scaling studies for heavy-quark observables calculated with an O(a^2)-improved fermion action on tree-level Symanzik improved gauge configurations. Lattices of 1/a = 2.0-3.7 GeV with an equal physical volume ~1.6 fm are used. The results are compared with the standard domain-wall and naive Wilson fermions.
Dr
Shigemi Ohta
(Institute of Particle and Nuclear Physics, KEK)
25/06/2014, 11:50
Talk
Analyses on possible systematics in some isovector nucleon observables in the RBC+UKQCD 2+1-flavor dynamical domain-wall fermion (DWF) lattice-QCD will be presented. The reports will be based mostly on the RBC+UKQCD Iwasaki+DSDR ensemble at pion mass of 170 MeV. The vector charge, axial charge, quark momentum and helicity fractions, and transversity are discussed. No autocorrelation issue...
Mr
Tim Harris
(Trinity College, University of Dublin)
25/06/2014, 11:50
I will present updated results from the FASTSUM collaboration on the bottomonium spectrum at finite temperature from lattice NRQCD on anisotropic $N_f=2+1$ Wilson clover ensembles.
Further systematic checks on the reconstruction of the spectral function at high temperatures where few correlator data are available will be discussed.
This is relevant to understand the reliability of the...
Dr
Urs Gerber
(Instituto de Ciencias Nucleares - Universidad Nacional Autonoma de Mexico)
25/06/2014, 11:50
We consider models with topological sectors and difficulties with their Monte Carlo simulation. In particular, we are concerned with the situation where a simulation has a very long auto-correlation time with respect to the topological charge. In such cases, reliable numerical measurements are only possible within single topological sectors. The challenge is to assemble such restricted...
Dr
Paulo Silva
(University of Coimbra)
25/06/2014, 11:50
The Z(N) dependence of the pure Yang-Mills gluon propagator, in the Landau gauge, is investigated at finite temperature for N=3. Special attention will be given to the behaviour near the critical temperature Tc. Our simulations show a complex pattern as expected in a first order phase transition. Furthermore, we identify an order parameter directly associated with the breaking of the SU(3)...
Mr
Javad Komijani
(Washington University in St. Louis)
25/06/2014, 12:10
We present final results for decay constants of charmed and strange pseudoscalar mesons, calculated on MILC ensembles with four dynamical quarks. The HISQ action is used for both the valence and sea quarks.
A straightforward analysis on the ensembles with physical quark masses, which avoids the need for chiral perturbation theory, is performed first.
We report the resulting values for...
Mr
Attila Pasztor
(MTA-ELTE Lendulet Lattice gauge theory research group/Eotvos University)
25/06/2014, 12:10
Finite temperature charmonium spectral functions in the pseudoscalar and vector channels are studied in lattice QCD with 2+1 flavours of dynamical Wilson quarks, on fine isotropic lattices (with a lattice spacing of 0.057fm), with a pion mass of 545MeV. The highest temperature studied is approximately 1.4Tc. Up to this temperature no significant variation of the spectral function is seen in...
Dr
Andrea Guerrieri
(Dipartimento di fisica e INFN Roma "Tor Vergata")
25/06/2014, 12:10
The very recent confirmation of the Z(4430) charged resonance by the LHCb experiment
strongly suggests the existence of QCD bound states with four quarks.
We report some preliminary results about hypothetical flavored tetraquark hadrons.
Such states are particularly amenable to Lattice QCD studies as their interpolating operators
do not overlap with those of ordinary hidden-charm mesons.
Arthur Dromard
(Goethe Universität, Frankfurt am Main)
25/06/2014, 12:10
Lattice QCD simulations tend to become stuck in a single topological sector at fine lattice spacing or when using chirally symmetric overlap quarks. In such cases physical observables differ from their full QCD counterparts by finite volume corrections, which need to be understood on a quantitative level. We discuss extensions of existing relations from the literature between correlation...
Dr
Parikshit Junnarkar
(Helmholtz Institut Mainz)
25/06/2014, 12:10
We present preliminary results on the axial form factor G_A(Q^2) and the induced pseudo-scalar form factor G_P(Q^2) of the nucleon. The relevant matrix elements were computed on CLS ensembles with N_f =2 non-perturbatively improved O(a) Wilson fermions at three lattice spacings, namely a = 0.050, 0.063, 0.079 fm. These calculations were performed with pion masses ranging from as low as m_pi =...
Prof.
Simon Catterall
(Syracuse University)
25/06/2014, 12:10
N=4 Yang-Mills may be formulated on the lattice in such a way as to
preserve one exact supersymmetry. This has remarkable consequences;
the beta function of the lattice theory vanishes at one loop, the moduli space of the theory survives to all orders of perturbation theory and a maximum of two fine tunings are required to take the continuum limit.
I will review the formulation and...
Mr
Roman Hoellwieser
(NMSU)
25/06/2014, 12:10
We present a method to smear (center projected) Z(2) vortices in order to obtain properties of the original (full) SU(2) configurations. In particular we address the problem that Z(2) configurations cannot be treated with overlap (or chirally improved) fermions due to their lack of smoothness. We develop a method to regain this smoothness and simultaneously maintain the center vortex...
Prof.
Constantia Alexandrou
(University of Cyprus)
25/06/2014, 12:30
Talk
We present results on the axial charges of the nucleon, the hyperons and charmed baryons
using a number of twisted mass fermions ensembles. This includes an $N_f=2$ ensemble with the physical value of the pion mass for which we also show results on the tensor structure of the nucleon.
Mr
Daniel Trewartha
(University of Adelaide)
25/06/2014, 12:30
The fundamental aspects of the QCD vacuum that are responsible for the dynamical generation of mass through chiral symmetry breaking is an ongoing source of debate. We investigate the role of centre vortices in dynamical mass generation using overlap fermions. The exact chiral symmetry that the overlap fermion action possesses yields a distinctive response to the underlying topology of the...
Prof.
Ethan Neil
(University of Colorado, Boulder)
25/06/2014, 12:30
We present the status of our updated D and B meson decay-constant analysis, based on the MILC Nf=2+1 asqtad gauge ensembles. Heavy quarks are incorporated using the Wilson clover action with the Fermilab interpretation. This analysis includes ensembles at five lattice spacings from a=0.045 to 0.15 fm, and light-quark sea masses down to 1/20 of the strange-quark mass. A complete...
Dr
Hiroshi Ohno
(Center for Computational Sciences, University of Tsukuba)
25/06/2014, 12:30
Quarkonium properties at finite temperature are studied with various quark masses in the range between those for the charm and bottom quarks. Our simulations are performed in quenched QCD with the $O(a)$-improved Wilson quarks on large and fine isotropic lattices at temperatures between about 0.7$T_c$ and 1.4$T_c$. At both vanishing and finite momenta we discuss temperature and quark mass...
Dr
Jeremy Green
(Institut für Kernphysik, Johannes Gutenberg-Universität Mainz)
25/06/2014, 12:30
Early results will be presented from a Lattice QCD study seeking a
bound H-dibaryon using Nf=2 flavors of O(a) improved Wilson fermions and a quenched strange quark. We solve the generalized eigenvalue problem constructed using a variational basis of interpolators consisting of the two independent local products of six positive-parity-projected quarks with the appropriate quantum numbers,...
Joel Giedt
(Rensselaer Polytechnic Institute)
25/06/2014, 12:30
We know from previous studies that the symetries of the
twisted Q-symmetric lattice theory are particularly powerful
in terms of protecting the long distance effective theory from unwanted
renormalizations. Here, it will be shown that rescalings of the
lattice fields imply that only two fine-tunings are required,
so that the N=4 theory is on a similar footing to clover fermions
in...
Chia Cheng Chang
(University of Illinois)
25/06/2014, 12:50
We present the status of our calculation of the D-meson mixing hadronic matrix elements for all five short-distance operators. We use the $N_{f}=2+1$ asqtad gauge field ensembles generated by the MILC collaboration involving four lattice spacings ranging from 0.12 to 0.045 fm and up/down to strange quark mass ratios as low as 0.05. For the charm quark we use the Sheikholeslami-Wohlert action...
Dr
Rajan Gupta
(Los Alamos National Lab)
25/06/2014, 12:50
This talk will present an update on the calculation of iso-vector nucleon charges g_A, g_S and g_T by the PNDME collaboration. The calculations are being done using clover valence quarks on 2+1+1 flavor HISQ lattices generated by the MILC collaboration at multiple values of the lattice spacing, light quark masses and lattice volumes. To extrapolate in the lattice volume, lattice spacing and...
David Schaich
(Syracuse University)
25/06/2014, 12:50
I will present results from numerical lattice studies of maximally (N=4) supersymmetric Yang--Mills theory with gauge group SU(2), based on a lattice formulation that exactly preserves one supersymmetry. While the pfaffian of the lattice theory is not manifestly real, direct measurements of the pfaffian show it to be approximately real and positive on all accessible lattice volumes. Studies...
Dr
Alexander Rothkopf
(Institute for Theoretical Physics, Heidelberg University)
25/06/2014, 12:50
We present the latest results from two projects focused on determining the temperature dependence of the heavy quark potential from lattice QCD. The real and imaginary part of this real-time potential is obtained from the position and width of the lowest lying peak in the Coulomb gauge Wilson line correlator spectral function [1]. Spectral information is extracted from Euclidean time data...
Hidenori Fukaya
(Osaka University)
25/06/2014, 12:50
Global topological charge tends to decorrelate very slowly or to even
freeze on fine lattice simulations, while local topological
fluctuations are expected to survive and lead to correct physical
results as long as the volume is large enough. We investigate this
issue on the recently generated configurations including dynamical
domain-wall fermions at a=0.08 fm and finer. We utilize the...
Dr
Zohreh Davoudi
(Institute for Nuclear Theory-University of Washington)
25/06/2014, 12:50
We explore the use of twisted boundary conditions in extracting the nucleon mass and the binding energy of two-baryon systems, such as the deuteron, from Lattice QCD calculations. Using the experimentally determined phase shifts and mixing angles, and utilizing the Luescher method extended to baryonic systems with twisted boundary conditions, we determine the expected energies of the deuteron...
Dr
Anthony Mezzacappa
(Oak Ridge National Laboratory)
26/06/2014, 09:00
Talk
Dr
Antonin Portelli
(University of Southampton)
26/06/2014, 11:30
Talk
Mr
Ciaran Hughes
(DAMTP, University of Cambridge)
26/06/2014, 14:15
Recently Lewis and Woloshyn's exploratory study using lattice NRQCD to study the radiative decay $\Upsilon(2S) \to \eta_b(1S) \gamma$ found that next-to-leading order ($v^6$) contributions were large compared to the leading order ($v^4) result. We explain this suppression of the $v^4$ term using a simple potential model. We then present our lattice QCD results obtained with three lattice...
Dr
Benjamin Svetitsky
(Tel Aviv University)
26/06/2014, 14:15
We have carried out a Schrodinger-functional calculation for the Abelian gauge theory with Nf=2 four-component fermions in three dimensions. We find no fixed point in the beta function, meaning that the theory is confining rather than conformal.
Mr
Michael Lujan
(The George Washington University)
26/06/2014, 14:15
Talk
Knowledge of the electric polarizability is crucial to understand the interactions of hadrons with electromagnetic fields. The neutron polarizability is very sensitive to the quark mass and is expected to diverge in the chiral limit. Here we present results for the electric polarizability of the neutron, neutral pion, and neutral kaon on eight ensembles with nHYP-smeared clover dynamical...
Prof.
Apoorva Patel
(Indian Institute of Science, Bangalore, India)
26/06/2014, 14:15
A specific unitary evolution operator can be constructed in many
different ways, corresponding to different Hamiltonian trajectories
between the desired end-points. An optimal trajectory can then be
selected to make the evolution have the best computational complexity
and control over errors. Using Grover's quantum search algorithm as
an explicit example, it is shown that the complexity...
Prof.
Leonid Glozman Glozman
(University of Graz)
26/06/2014, 14:15
Using the overlap Dirac operator we remove its
lowest-lying eigenmodes from the valence quark
propagators and study evolution of the J=1 meson
masses. At the truncation energy about 50 MeV we
observe a degeneracy of all possible U(2)_L * U(2)_R
multiplets, i.e. the observed quantum levels have
a symmetry larger than U(2)_L * U(2)_R and their
energy does not depend on the spin...
Takashi Umeda
(Hiroshima University)
26/06/2014, 14:15
The fixed scale approach has various advantages to calculate the QCD equation of state on lattices. In this approach a series of temperatures are realized with single coupling parameters. Therefore zero temperature subtractions are common, and conditions for the line of constant physics are automatically satisfied. We test the fixed scale approach to study thermodynamics of SU(3) gauge theory...
Dr
Patrick Fritzsch
(Humboldt University Berlin)
26/06/2014, 14:15
We review our new strategy and current status towards a high precision computation of the Lambda parameter from three-flavour simulations in QCD. To reach this goal we combine specific advantages of the Schroedinger functional and gradient flow couplings.
Dr
Holger Perlt
(Leipzig university)
26/06/2014, 14:35
Renormalization factors are needed to related lattice quantities to their corresponding continuum counterparts. In order to renormalize singlet observables one has to include connected and disconnected diagrams. Especially, the disconnected contributions are very difficult to calculate using the standard three-point function technique. The Feynman-Hellmann method provides the possibility to...
Mr
Daniel Körner
(FSU Jena)
26/06/2014, 14:35
We study the non-perturbative renormalization group flow of the
nonlinear O(N) sigma model in two and three space-time dimensions
using a scheme that combines an effective local Hybrid Monte Carlo
update routine, blockspin transformations and a Monte Carlo demon
method. In two dimensions our results verify perturbative
renormalizability. In three dimensions, we determine the flow...
Mr
Ryo IWAMI
(Niigata University)
26/06/2014, 14:35
We discuss the reweighting method aiming numerical studies of QCD at finite density, in which the Monte-Carlo method cannot be applied directly. One of the most important problems in the reweighting method is the overlap problem. To solve the problem, we propose the following reweighting method: simulations are performed at several simulation points and the analysis is done combining all data....
Dr
Walter Freeman
(George Washington University)
26/06/2014, 14:35
Talk
The contribution of the sea quark charges is a large uncertainty in lattice calculations of hadron polarizabilities; we present an update in our use of perturbative reweighting in the quark charge to address this issue. The difficult aspect of this calculation is the stochastic estimation of the weight factor expansion coefficients. We use aggressive (large-N) dilution, consisting of...
Judah Unmuth-Yockey
(University of Iowa)
26/06/2014, 14:35
We study the two-dimensional O(3) model on the lattice using the Tensor
Renormalization Group (TRG) approach, with the goal of understanding asymptotic
scaling at both the large volume, and large beta limit. Harmonic analysis on the
Boltzmann weight introduces a sign problem into the partition function, which
makes the model difficult to study with the Worm Algorithm. The TRG...
Dr
JONG-WAN LEE
(City College of New York)
26/06/2014, 14:55
Talk
We discuss the resolution of inconsistencies between the background field method in lattice QCD and the effective field theory matching conditions. Lack of on-shell conditions in lattice QCD with time-dependent background fields requires that operators related by equations of motion in the effective field theory should be retained in the action to describe the Green's function correctly. As a...
Felix Stollenwerk
(Humboldt University Berlin)
26/06/2014, 14:55
We develop a strategy for the non-perturbative determination of the O(\(a\))-improvement coefficient \(c_{\rm sw}\) for Wilson fermions with massive sea quarks. The improvement condition is defined via the PCAC relation in the Schrödinger functional. It is imposed along a line of constant physics designed to be close to the correct mass of the charm quark. The numerical work uses the...
Dr
Roger Horsley
(University of Edinburgh)
26/06/2014, 14:55
SU2 isospin breaking effects in hadron octet and decuplets
are due to a combination of up and down quark mass differences
and electromagnetic effects. Usually these masses difference are small.
Between the Sigma and Lambda the splitting is much larger
due to mixing between these states. We determine the QCD mixing matrix
and hence find the mixing angle and mass splitting. Provided
the...
Dr
Agostino Patella
(CERN and Plymouth University)
26/06/2014, 14:55
The energy-momentum tensor in lattice gauge theories requires renormalization because of the breaking of Poincare' group. The Wilson flow can be used in principle to set up non-perturbative, well-defined and, possibly, practically convenient strategies to define
a properly renormalized energy momentum tensor. I will present some preliminary data in this direction.
Dr
Maksim Ulybyshev
(Regensburg University)
26/06/2014, 14:55
Tight-binding model of Graphene with vacancies in crystal structure was studied within the framework of Hybrid Monte Carlo simulations.
Antiferromagnetic ordering is observed in the vicinity of the vacant sites. Mass gap is extracted from the calculations of the two-point Euclidean Green function. It is demonstrated that even a relatively small concentration of vacancies can lead to opening a...
Mr
Norbert Trombitas
(Eotvos Lorand University)
26/06/2014, 14:55
We study 2+1 flavour QCD thermodynamics using Wilson fermions in the fixed scale approach. The temperature dependence of the renormalized chiral condensate, quark number susceptibility and Polyakov loop is determined at three pion masses down to 280~MeV. Four lattice spacings are used allowing for a controlled continuum limit.
Dr
Alexander Molochkov
(Far Eastern Federal University)
26/06/2014, 14:55
The most important probes for the phase states of a four-dimensional gauge field theory are the Wilson and t'Hooft line operatros that are defined on one-dimensional curves in the space-time. However, for more detail understanding of four-dimensional gauge field theory dynamics and vacuum topology we need additional probes expressed by operators defined on the subspaces with higher dimensions....
Mr
Mark Wurtz
(York University)
26/06/2014, 15:15
Gauge-invariant sources with a hydrogen wave function shape are constructed for bottomonium two-point correlation functions using the free-form smearing technique. The bottomonium spectrum is extracted from free-form smeared correlation functions. Results are compared with conventional smearing techniques.
Mr
Alexander Nikolaev
(Far Eastern Federal University)
26/06/2014, 15:15
Tight-binding model of the AA-stacked bilayer graphene with screened
electron-electron interactions has been studied using the Hybrid Monte
Carlo simulations on the original double-layer hexagonal lattice.
Instantaneous screened Coulomb potential is taken into account using
Hubbard-Stratonovich transformation. G-type antiferromagnetic ordering has been studied and the phase transition with...
Dr
Stefan Krieg
(Forschungszentrum Juelich GmbH/Wuppertal University)
26/06/2014, 15:15
I will review results for the Equation of State of QCD, in particular I will give an update on our calculation that includes a dynamical charm quark.
Prof.
Jacek Wosiek
(Jagellonian University)
26/06/2014, 15:15
Screening of external charges by electric fluxes induced by periodic
boundary conditions in two dimensional gauge theories will be discussed.
Subsequently, the less known problem of introducing sources with arbitrary
charge, i.e. non-congruent with an elementary one, will be presented and
elaborated. Finally the new, classical continuum limit of lattice
formulation will be proposed and...
Prof.
Masanori Okawa
(Hiroshima University)
26/06/2014, 15:15
Last year, we proposed a new method to extract string tension using 4-dimensional smearing method (PL B718 (2013) 1524). In this talk we first show that results using smearing method are equivalent to those obtained by Wilson flow once the time step \epsilon is sufficiently small. We then demonstrate the practical advantage of our method by applying it to the calculation of Creutz ratio in...
Maarten Golterman
(San Francisco State University)
26/06/2014, 15:15
When a subgroup of the flavor symmetry group of a gauge theory is
weakly coupled to additional gauge fields, the vacuum tends to
align such that the gauged subgroup is unbroken. At the same time,
the lattice discretization typically breaks the flavor symmetry
explicitly, and can give rise to new lattice-artifact phases with
spontaneously broken symmetries. We discuss the interplay of...
Kadir Utku Can
(Tokyo Institute of Technology)
26/06/2014, 15:35
The electromagnetic form factors of \Sigma_c, \Xi_cc, \Omega_c and \Omega_cc baryons are computed and their electric and magnetic charge radii as well as their magnetic moments are extracted in 2+1 flavor Lattice QCD. Extrapolated physical point results show that the charge radii and magnetic moments are smaller compared to those of, e.g., proton. Investigating the individual quark...
Dr
Dominik Smith
(TU Darmstadt)
26/06/2014, 15:35
We report on the status of our ongoing Hybrid-Monte-Carlo simulations of the tight-binding model for the electronic properties of graphene, using a realistic potential for the two-body interactions.
Our short-range interactions thereby include the partial screening due to electrons in higher energy states from ab initio calculations based on the constrained random phase approximation...
Mr
Masanori for HAL QCD Coll Yamada
(University of Tsukuba)
26/06/2014, 15:35
We report our results of central potential between two Omega baryons
from 2+1 flavor full Lattice QCD simulation.In the past studies, there is
a possibility that some decuplet baryons have a bound state.
However, almost all decuplet baryons are unstable due to decays via the strong interaction.
An exception is the Omega decuplte baryon, which is stable against the strong decays,
so its...
Tanmoy Bhattacharya
(LANL)
26/06/2014, 15:35
The HotQCD Collaboration has calculated the equation of state in 2+1 flavor QCD at zero net baryon density using the Highly Improved Staggered Quark (HISQ) action. The
strange quark mass was set to its physical value and the light (up/down)
quark masses used correspond to a pion mass of 160 MeV in the continuum
limit. Lattices with temporal extent Nt=6, 8, 10 and 12 were used, and the...
Dr
Daniel Nogradi
(Eotvos University)
26/06/2014, 15:35
The Yang-Mills gradient flow is considered in lattice perturbation theory at leading order of the gauge coupling and O(a^8) in the lattice spacing. Improved actions are incorporated for the gauge action, the flow itself and the observable for E(t). The results lead to a setup with O(a^6) improvement at tree level.
Mr
Shinya Gongyo
(Kyoto University)
26/06/2014, 15:35
We study numerically the phase structure in two dimensions
with SU(2) gauge-Higgs coupling.
We calculate the static potential from Wilson Loop, W propagator
and the order parameter related to a transition between the confinement-like
phase and Higgs-like phase. Our results suggest that there
is a confinement-like phase and Higgs-like phase, even in two dimensions.
In the confinement-like...
Stefan Sint
(Trinity College Dublin & NIC@DESY-Zeuthen)
26/06/2014, 15:55
The gradient flow has become a very useful tool both for scale setting and for defining suitable finite volume schemes for the gauge coupling. However, surprisingly large cutoff effects have been observed in some cases. We here investigate these effects at leading order in perturbation theory and reproduce qualitative features that have previously been observed in the context of scale setting....
Dr
Oleg Pavlovskiy
(Moscow State University)
26/06/2014, 15:55
New formulation of path integrals for relativistic quantum systems will discussed. Influence of the relativistic effects on the properties of quantum systems will be studied by means of the Monte Carlo method. A generalization of this approach to the case the path integral quantization of the Born-Infeld field theory will also discussed.
Mr
Christian Shultz
(Old Dominion University)
26/06/2014, 15:55
Talk
We present a progress update on an ongoing calculation aimed at extracting photocouplings in the light-quark sector from radiative matrix elements computed using lattice QCD. These couplings drive the rate of photo production of mesons, of particular interest are exotic and hybrid mesons which while present in lattice calculations have yet to be observed experimentally. The use of distillation...
Dr
Prasad Hegde
(Central China Normal University)
26/06/2014, 15:55
Hydrodynamic models of heavy-ion collisions have increasingly begun to rely on lattice results for the Equation of State. While the lattice has the advantage of being a first-principles approach to QCD, the notorious sign problem prevents a direct determination of the equation of state and other thermodynamic observables at finite chemical potential $\mu_B$.
Quark number susceptibilities...
Mithat Unsal
(North Carolina State University)
26/06/2014, 15:55
This talk presents a summary of our current understanding of confinement problem in non-abelian gauge theories. It is dedicated to the memory of Pierre van Baal, who contributed to the field significantly.
I will review recent semi-classically calculable realization of confinement in various gauge theories. In particular, I will describe the role of monopole-instantons(realized by van...
Prof.
Sinead Ryan
(Trinity College Dublin)
26/06/2014, 16:15
Preliminary results from a study of $DK$ and $D\pi$ scattering
are presented using a set of anisotropic $N_f=2+1$ dynamical gauge field
configurations generated by the Hadron Spectrum Collaboration. The
variational method with a large operator basis is used in two lattice
volumes to determine the excitation spectra of open charm mesons with
the relevant scattering states containing one...
Mr
Benjamin Owen
(University of Adelaide)
26/06/2014, 16:15
Talk
Over the past decade there has been significant experimental interest into the electromagnetic excitation of nucleon resonances and their underlying structure. Given the large body of data that now exists, it is interesting to consider the expectations presented by QCD. Correlation matrix techniques present us with the ideal approach to extracting matrix elements of hadronic excitations....
Dr
Christopher Monahan
(College of William and Mary)
26/06/2014, 16:15
We propose a new ``smeared'' operator product expansion (sOPE) in
which the set of local operators in the OPE are replaced by their locally smeared counterparts, generated by the gradient flow. The flow time, or smearing, parameter serves as a regulator for both Wilson coefficients and operator products. Matrix elements determined
nonperturbatively on the lattice using smeared degrees of...
Mr
Semen Valgushev
(Institute for Theoretical and Experimental Physics)
26/06/2014, 16:15
The results of numerical simulation of graphene effective field theory in external magnetic field are presented. The numerical simulation is performed using noncompact (3+1)-dimensional Abelian lattice gauge fields and (2+1)-dimensional staggered lattice fermions. The dependences of fermion condensate and conductivity on the dielectric permittivity of the substrate for different values of...
Prof.
Sasa Prelovsek
(University of Ljubljana)
27/06/2014, 09:00
Talk
Dr
Denes Sexty
(Institut für Theoretische Physik, Universität Heidelberg)
27/06/2014, 09:45
Talk
Dr
Alberto Ramos
(NIC @ DESY, Zeuthen)
27/06/2014, 10:15
Talk
Prof.
Tetsuya Onogi
(Osaka University)
27/06/2014, 11:45
Talk
The emergence of massless Dirac fermion in graphene has attracted attention in recent years due to the remarkable features. The tight-binding honeycomb lattice hamiltonian to explain this feature has a close analogy with "the staggered fermion" which is widely used in lattice gauge theory. Employing the position space formalism developed in lattice gauge theory, we reformulate the...
Ms
Yuko Murakami
(Hiroshima University)
27/06/2014, 14:15
We investigate the universality of Möbius Domain Wall Fermions (MDWF) in the Schrödinger Functional (SF) scheme at tree level. We introduce the SF boundary condition to the MDWFs by adding a temporal boundary operator. When the fifth dimensional parameters of the MDWF are a constant, this construction seems to be natural according to the Luescher’s universality prescription for the overlap...
Dr
Francesco Di Renzo
(University of Parma and INFN)
27/06/2014, 14:15
In the context of thimble regularization of lattice field theories we are developing a new simulation algorithm. The main difficulty is to devise a sampling of configurations on a non-trivial manifold, which is defined as the hypersurface formed by the union of all paths of steepest descent of the complex action ending in a given saddle point. The main point with the new algorithm is the...
Richard Lau
(University of Oxford)
27/06/2014, 14:15
We present our current results for the deconfining temperatures in SO(N) gauge theories in 2+1 dimensions. SO(2N) theories may help us to understand QCD at finite chemical potential since there is a large-N orbifold equivalence between SO(2N) QCD-like theories and SU(N) QCD and SO(2N) theories do not have the sign problem present in QCD. We show that the deconfining temperatures in these two...
Prof.
Gerrit Schierholz
(DESY)
27/06/2014, 14:15
First results on electromagnetic mass splittings of octet mesons and baryons from a fully dynamical simulation of QCD+QED are presented.
Ms
Emilie Huffman
(Duke University)
27/06/2014, 14:15
We present a solution to the sign problem in a class of particle-hole
symmetric Hamiltonian lattice fermion models on bipartite lattices
using the idea of fermion bags. The solution remains valid when
the particle hole symmetry is broken through a staggered chemical
potential term. This solution allows, for the first time, simulations
of some massless four-fermion models with minimal...
Marina Marinkovic
(University of Southampton)
27/06/2014, 14:15
Talk
We present steps towards the computation of the leading-order hadronic contribution to the muon anomalous magnetic moment on RBC/UKQCD physical point DWF ensembles. We discuss several methods for controlling and reducing uncertainties associated to the determination of the HVP form factor.
Mr
Matthias Puhr
(University Regensburg)
27/06/2014, 14:35
The overlap Dirac operator at finite chemical potential can be efficiently computed with the two-sided Lanczos algorithm. Compared with other methods the Lanczos algorithm has the advantage that it takes into account information about the source vector when constructing an approximation to the overlap operator.
In order to study transport coefficients in terms of correlators of conserved...
Prof.
Artan Borici
(Uiversity of Tirana)
27/06/2014, 14:35
It is well known that Crank-Nicolson discretization scheme is second order accurate in time. Its application in the case of the Dirac operator leads to a lattice theory with reduced doublers and broken parity. Adding a 3-space Wilson term one obtains a single fermion which is second order accurate in time. In the case of an imaginary term the doubler degeneracy is lifted and the ground state...
Prof.
Claude Bernard
(Washington University St. Louis)
27/06/2014, 14:35
We report on the MILC Collaboration calculation of electromagnetic effects on light pseudoscalar mesons. The simulations employ asqtad staggered dynamical quarks in QCD plus quenched photons, with lattice spacings varying from 0.12 to 0.06 fm. Finite volume corrections for the MILC realization of lattice electrodynamics have been calculated in chiral perturbation theory theory and applied to...
Dr
Mateusz Koren
(IFT UAM-CSIC Madrid)
27/06/2014, 14:35
We analyze 2+1 dimensional Yang-Mills theory regularized on a lattice with twisted boundary conditions in the spatial directions. In previous work it was shown that the observables in the non-zero electric flux sectors obey the so-called x-scaling, i.e. depend only on the variable x~NL/b and the magnetic flux, given by the parameters of the twist (L being the length of the spatial torus and b...
Dr
Michael Buchoff
(Institute for Nuclear Theory)
27/06/2014, 14:35
One intriguing coincidence in cosmology is that the observed dark matter and baryonic densities are within a factor of 5 in magnitude. A natural explanation for such a coincidence is that the origin of the dark matter density is intimately related to the early universe processes that led to the baryon asymmetry. Many of these “asymmetric” dark matter scenarios favor a strongly coupled...
Dr
Roberto Pellegrini
(College of Science, Swansea University, Swansea, SA2 8PP, UK)
27/06/2014, 14:35
We present a novel algorithm to compute the density of states, which is proven to converge to the correct result.
The algorithm is very general and can be applied to a wide range of models, in the frameworks of statistical mechanics and lattice gauge theory.
All the thermal or quantum expectation values can then be obtained by a simple integration of the density of states.
As an...
Prof.
Lucini Biagio
(Swansea University)
27/06/2014, 14:55
Recently, a new and efficient algorithm (the LLR method) has been proposed for computing density of states in statistical systems and gauge theories. In this talk, we explore whether this novel density of state method can be applied to numerical computations of observables in systems for which the action is complex. To this purpose, we introduce a generalised density of states, in terms of...
Mr
Hanno Horch
(University of Mainz)
27/06/2014, 14:55
Talk
We compute the Adler function from vacuum polarization data with
twisted boundary conditions using numerical derivatives. The study is
based on CLS ensembles with two flavours of O(a) improved Wilson
fermions. To describe the momentum dependence and to extrapolate the
lattice data to the continuum limit and to the physical point, we
perform a combined fit and compare our results for the...
Dr
Renwick Hudspith
(York University)
27/06/2014, 14:55
We provide details of our implementation of a non-linear conjugate gradient method for Landau and Coulomb gauge fixing with Fourier acceleration. We find clear improvement over the Fourier accelerated steepest descent method, with the average time taken for our algorithm to converge to a fixed, high accuracy, being lower by a factor of 2 to 4 for several lattice volumes.
Dr
Santanu Mondal
(Eotvos University, Institute for Theoretical Physics, Budapest 1117, Hungary)
27/06/2014, 14:55
The strongly coupled near-conformal gauge theory with two fermion flavors in the two index symmetric (sextet) representation of the SU(3) color gauge group is the minimal realization of the composite Higgs mechanism. We discuss the baryon mass spectrum in this theory using staggered fermion operators to identify dark matter candidates.
Mr
Venkitesh Ayyar
(Duke University)
27/06/2014, 14:55
Massless fermions can become massive due to interactions through the mechanism of Spontaneous Symmetry Breaking (SSB). This mode of mass generation is popular and has been used in the Standard Model. Here, we explore
the possibility of fermions acquiring a mass through interactions, but without SSB.\\
We consider a fermion system on a cubical lattice and introduce an on-site four-fermion...
Liuming Liu
(University of Bonn)
27/06/2014, 14:55
Recently a charged resonance-like structure $Z_c(3900)$ has been observed in several experiments. The invariant mass of this structure is close to the DD* threshold, and one possible interpretation is a molecular bound state formed by the D and $\bar{D}*$ mesons. We study the low-energy scattering of $D\bar{D}^*$ using lattice QCD with N_f = 2 twisted mass fermion configurations with three...
Dr
Axel Maas
(University of Jena)
27/06/2014, 14:55
The Higgs sector of the standard model, the Higgs and the W/Z bosons, is a quite peculiar theory. Because of the Higgs effect, in some cases the observable particles, i.e. gauge-invariant bound states, have the same mass as the elementary particles. This is what makes perturbation theory in the electroweak sector possible. Under which condition this holds true is not only important for...
Mr
Luka Leskovec
(Institute Jozef Stefan)
27/06/2014, 15:15
We perform a lattice QCD simulation of the charmonium-like channel, where experiments recently found several manifestly exotic states named Zc+ with flavor content bar c c bar d u. In addition to identifying all the scattering states we also observe an additional level in the simulation, which we attribute to Zc+.
Hans-Peter Schadler
(University of Graz)
27/06/2014, 15:15
Generalized quark number susceptibilities have been proposed to be good probes for the phase transition in QCD and in the search of a critical point. In this work we explore the possibilities of the expansion in the fugacity parameter $e^{\mu\beta}$ which has features which make, in particular, quark number related bulk observables easily accessible. We will present results at finite chemical...
Dr
Vincent Drach
(CP3 Origins &amp; DIAS)
27/06/2014, 15:15
We investigate non perturbatively scattering properties of Goldstone Bosons in SU(2) gauge theory with two Wilson fermions in the fundamental representation. Such a theory can be used to build extensions of the Standard Model that unifies Technicolor and pseudo Goldstone composite Higgs models. The leading order contribution to the scattering amplitude of Goldstone bosons at low energy is...
Dr
Pavel Buividovich
(Regensburg University)
27/06/2014, 15:15
We study interacting Dirac fermions with chiral imbalance (modelled by a chiral chemical potential) in the mean-field approximation and find that the chiral imbalance is strongly enhanced due to spontaneous chiral symmetry breaking. We then consider the Chiral Magnetic Effect (CME) in the linear response approximation and find that in a phase with broken chiral symmetry the CME current is...
Gregorio Herdoiza
(KPH Mainz and IFT Madrid)
27/06/2014, 15:15
Talk
The QCD contributions to the vacuum polarisation function are
responsible for a large fraction of the theoretical uncertainty in the
running of the QED coupling and therefore limit its impact on
electroweak precision tests. We use lattice simulations with N_f=2
O(a) improved Wilson fermions to determine the Adler function in a
broad range of momentum transfer Q^2. The running of the QED...
Dr
Axel Cortes Cubero
(City University of New York)
27/06/2014, 15:15
Massive Yang-Mills theory is known to be renormalizable in 1+1 dimensions. The gluon mass is introduced by coupling the gauge field to an SU(N) principal chiral nonlinear sigma model. The proof of renormalizability relies on the asymptotic freedom of the sigma model. However, renormalization forces the gluon mass to infinity. The continuum theory is in a confined phase rather than a Higgs...
Philippe de Forcrand
(ETH Zurich)
27/06/2014, 15:35
We study the Hosotani mechanism on the lattice and show with the use of
gauge invariant observables that SU(3) can break either to SU(2)xU(1) or
U(1)xU(1). The novelty in this study is the strict gauge invariance of
the observables used.
We take advantage of the inability of a U(1) flux to decay in the continuum
limit. One interesting consequence is that the SU(2) and U(1)...
Mr
Matthew Spraggs
(University of Southampton)
27/06/2014, 15:35
I demonstrate pyQCD, a native Python library providing an extensible API for single-node lattice measurements and simulations. Boost.Python is used to wrap the underlying C++ code and expose an interface to Python for the generation of propagators and configurations, both of which are returned as numpy ndarray types. The library can take advantage of GPU technology by using CUDA where possible...
Mr
Simon Mages
(University of Regensburg)
27/06/2014, 15:35
This talk is on recent efforts to determine the shear viscosity $\eta$ in the deconfined phase from lattice QCD. The main focus is on the integration of the Wilson flow in the analysis to get a better handle on the infrared behaviour of the spectral function which is relevant for transport. Also the non-perturbative renormalization strategy applied for the energy momentum tensor is discussed....
Ms
Jana Günther
(Bergische Universität Wuppertal)
27/06/2014, 15:35
Since the discovery of the Higgs particle at the LHC it is possible to investigate the equation of state for the electro weak transition in the SU(2)-Higgs-model at physical parameters. We will present a line of constant physics and preliminary results on the equation of state for small Nt values. The data was obtained by simulation with a combined heatbath and overrelaxation algorithm.
Christoph Lehner
(BNL)
27/06/2014, 15:35
We explore ways to decrease parts of the finite volume error and apply the method to the hadronic contributions to muon g-2.
Mr
Bartosz Kostrzewa
(Humboldt Universität zu Berlin, Institut für Physik, Newstonstr. 15, 12489 Berlin, Germany / NIC, DESY, Zeuthen, Platanenallee 6, D-15738 Zeuthen, Germany)
27/06/2014, 15:35
In this contribution, updated results from simulations by the
European Twisted Mass Collaboration at the physical point using
Wilson twisted mass fermions with a clover term are presented. We
discuss results for the pseudoscalar decay constants $f_K$, $f_D$
and $f_{D_s}$ and the corresponding masses. In addition, we provide
evidence for a largely reduced flavour symmetry breaking in...
Daping Du
(Syracuse University)
27/06/2014, 16:30
We update the lattice calculation of the $B\to\pi$ semileptonic form factors with a focus on the applications to the CKM matrix element $|V_{ub}|$. We use the MILC AsqTad 2+1-flavor lattice configurations at four lattice spacings and compute the matrix elements using the full-QCD valence quarks. We extrapolate the lattice data to continuum physics using the staggered chiral perturbation theory...
Dr
James Zanotti
(University of Adelaide)
27/06/2014, 16:30
Talk
By introducing an external spin operator to the fermion action, the
quark-line connected matrix elements relevant for quark spin fractions
of hadrons are extracted from the linear response of the hadron
energies using the Feynman-Hellmann (FH) theorem. At the SU(3)-flavour
symmetry point, we find that the connected quark spin fractions are
universally in the range 55-70% for vector mesons...
Dr
Jeff Greensite
(San Francisco State University)
27/06/2014, 16:30
I explain the “relative weights” strategy for deriving effective Polyakov line actions, at finite chemical potentials, from the underlying lattice gauge theories. Gauge-Higgs and heavy quark models are the examples considered. The effective Polyakov line theories still have a severe sign problem, and I compare results obtained using mean field and complex Langevin methods to solve such theories.
Dr
pietro giudice
(University of Muenster)
27/06/2014, 16:30
We summarize the last results of our collaboration concerning
N=1 supersymmetric Yang-Mills theory in four dimensions on the lattice.
We investigate the expected formation of supersymmetric multiplets of the
lightest particles and the behaviour of the topological susceptibility
approaching the supersymmetric and the continuum limit of the theory.
Mr
Jakob Simeth
(University of Regensburg)
27/06/2014, 16:30
The quantification and subtraction of hypercubic lattice artifacts is essential for the calculation of non-perturbative renormalization constants. It has been shown that for the RI'-MOM scheme a large part of these artifacts can be calculated using Lattice Perturbation Theory (LPT), but these calculations are typically restricted to 1-loop order and to bilinear quark operators with one...
Dr
Michele Brambilla
(Università di Parma and INFN)
27/06/2014, 16:50
In recent years Numerical Stochastic Perturbation Theory (NSPT) has proven to be a viable tool to perform perturbative computation at high order on the lattice. Despite final results are equivalent to standard Feynman diagrams the approach is rather different and allows a numerical implementation similar to usual (nonperturbative) MonteCarlo.
I will discuss final results for the computation...
Mr
DANIEL ROBAINA
(Institute of Nuclear Physics. Johannes Gutenberg University Mainz)
27/06/2014, 16:50
We investigate the low-temperature phase of QCD and the crossover region with two light flavors of quarks. The chiral expansion around the point $(T, m_q = 0)$ in the temperature vs. quark-mass plane indicates that a sharp real-time excitation exists with the quantum numbers of the pion. We determine its dispersion relation and test the applicability of the chiral expansion. The time-dependent...
Raza Sufian
(University of kentucky)
27/06/2014, 16:50
Talk
We present a lattice QCD calculation of the glue helicity $\Delta G$ in the nucleon for the first time.
It is recently shown that the first moment of the glue helicity distribution can be obtained through the product
of the the electric field $\vec{E}$ and the gauge field in the Coulomb gauge $\vec{A}_C$, i.e.
$\vec{E} \times \vec{A}_C$ in the infinite momentum frame. We used the gauge...
Prof.
Makoto Sakamoto
(Kobe University)
27/06/2014, 16:50
We propose a lattice model of a complex SUSY quantum mechanics which realizes the non-renormalization theorem on lattice. In our lattice model, the Leibniz rule in the continuum, which cannot hold on lattice due to a no-go theorem, is replaced by the cyclic Leibniz rule (CLR) for difference operators. It is shown that the CLR allows two of four supercharges of the continuum theory to preserve...
Dr
Taichi Kawanai
(Brookhaven National Laboratory)
27/06/2014, 16:50
We report results for the B→π and B_s→K semileptonic form factors using lattice QCD with domain-wall light quarks and relativistic b-quarks. We use the 2+1 flavor domain-wall Iwasaki gauge configurations generated by the RBC and UKQCD collaborations at two lattice spacings of a~0.08fm and a~0.11fm. Our lightest pion mass is about 290MeV. We perform the chiral and continuum extrapolations using...
Dr
Michael Glatzmaier
(University of Kentucky)
27/06/2014, 17:10
We discuss recent preliminary results for a lattice calculation of the glue helicity $\Delta_G$ in the Coulomb gauge. We have used the gauge field tensor defined from the overlap Dirac operator. The calculation is carried out with valence overlap quarks on 2+1 DWF gauge
configurations on the $24^3 \times 64$ lattice which corresponds to a pion mass of 330 MeV. Finally, we discuss the...
Michael Engelhardt
(New Mexico State University)
27/06/2014, 17:10
Talk
Lattice QCD calculations of transverse momentum-dependent
parton distributions (TMDs) in a nucleon are performed
based on a definition of TMDs via hadronic matrix elements
of quark bilocal operators containing staple-shaped gauge
connections. A parametrization of the matrix elements in
terms of invariant amplitudes serves to cast them in the
Lorentz frame preferred for the lattice...
Dr
Yuzhi Liu
(University of Colorado, Boulder)
27/06/2014, 17:10
We study the SU(4) lattice gauge theory with Nf=2 Dirac fermions in the anti-symmetric two index (sextet) representation (the ``SU(4)/sextet" theory). This is a real fermion representation, which allows simulation at non-zero chemical potential with no sign problem. In addition, ``SU(4)/sextet'' is an interesting generalization of QCD, allowing direct exploration of an alternate large-N_c...
Mr
Andrey Kotov
(ITEP, Moscow)
27/06/2014, 17:10
We present preliminary results of the study lattice SU(2) QCD phase diagram with chiral chemical potential. The simulation is carried out with dynamical staggered fermions without rooting. The dependences of the chiral density, Polyakov loop, chiral condensate and corresponding susceptibilities on the chiral chemical potential and temperature are measured.
Mr
Oleg Kochetkov
(University of Regensburg)
27/06/2014, 17:30
We study the influence of an external magnetic field on the deconfinement transition in two-flavour lattice QCD
with physical quark charges. We use dynamical overlap fermions without any approximation such as fixed topology and
perform simulations on a 16^3×6 lattice and at a pion mass around 500 MeV.
The pion mass (as well as the lattice spacing) was determined in the independent runs on...
Mr
Jacob Finkenrath
(University of Wuppertal)
27/06/2014, 17:30
Most of today's lattice simulations are performed in the isospin symmetric limit in the light quark sector. A technique with moderate numerical cost to include effects of isospin breaking in the sea quark sector is mass reweighting. We will give a summary of the recent results on fine lattices with light quark masses.
In general reweighting corrects the weight of an ensemble which is...
Dr
Kei-ichi Nagai
(KMI, Nagoya University)
27/06/2014, 17:30
We (LatKMI Collaboration) present the first observation of a flavor-singlet scalar meson as light as the pion in Nf=8 QCD on the lattice, using the HISQ action. Such a light scalar meson can be regarded as a composite Higgs with mass 125 GeV, and may be a technidilaton, a pseudo Nambu-Goldstone boson of the approximate scale symmetry in walking technicolor.
We also report the update about...
Jonathan Flynn
(University of Southampton)
27/06/2014, 17:30
Talk
We discuss nonperturbative renormalisation of the leading-twist flavour non-singlet operators needed for the calculation of the first and second moments of light-meson distribution amplitudes. On the lattice we use a regularisation-independent symmetric (or non-exceptional) momentum scheme, RI/SMOM, which, for the second moment, allows us to include mixing with a total-derivative operator. We...
Heechang Na
(University of Utah)
27/06/2014, 17:30
We present our recent results on B to D, Bs to Ds, and Bs to K Standard Model tree level semileptonic decays.
We have used MILC Nf=2+1 asqtad gauge configurations with two lattice spacings.
For the valence quarks, we used NRQCD bottom quarks and HISQ light and charm quarks.
The B to D and Bs to Ds semileptonic form factors can be used for better determination of the Bs to [mu^+ mu^-]...
Dr
Akaki Rusetsky
(HISKP, University of Bonn)
27/06/2014, 17:50
Using the non-relativistic effective field theory framework in a finite volume, we discuss the extraction of the $\Delta N\gamma^*$ transition form factors from lattice data. A counterpart of the L\"uscher approach for the matrix elements of unstable states is formulated. In particular, we thoroughly discuss various kinematic settings, which are used in the calculation of the above matrix...
Mr
Hiroshi Ohki
(Kobayashi-Maskawa Institute for the Origin of particles and the universe)
27/06/2014, 17:50
In the search for a composite Higgs boson in walking technicolor models, many flavor QCD is an attractive candidate. Particularly promising is the Nf=8 theory, which has been found to have a composite flavor-singlet scalar as light as the pion. Based on simulations of this theory with the HISQ action at various fermion masses in the LatKMI collaboration, we will present our preliminary results...
Jon Bailey
(Seoul National University)
27/06/2014, 17:50
The CKM matrix element |V_{cb}| can be extracted by combining experimentally determined branching fractions for B to D(*) ell nu decays with form factors from the lattice. While successful, the precision of this approach has been limited by heavy-quark discretization effects. An improved version of the Fermilab action, the Oktay-Kronfeld action, can be used to reduce heavy-quark...
Mr
Marco Mariti
(University of Pisa & INFN)
27/06/2014, 17:50
We present improved results regarding our determination of the
magnetic susceptibility in QCD. We discuss also preliminary
data on higher order terms contributions in B to the free energy
and to the relative increase in the pressure.
Prof.
Haralambos (Haris) Panagopoulos
(Univeristy of Cyprus)
27/06/2014, 17:50
We compute the difference in the renormalization of flavor singlet and nonsinglet fermion bilinear operators, to 2 loops in perturbation theory. Our results are applicable to a rather wide class of lattice actions with Symanzik improved gluons, stout links and clover fermions, including the Twisted Mass and SLiNC actions.
Ludmila Levkova
(University of Utah)
27/06/2014, 18:10
We present results for the pressure of the quark-gluon plasma in the presence of a strong
magnetic filed, calculated using a Taylor expansion in the field to 4th order.
Our method does not require quantization of the magnetic filed and is
computationally cheaper than calculations on ensembles generated with explicit magnetic
fields.
Vittorio Lubicz
(Universita' Roma Tre)
27/06/2014, 18:10
We describe our study of the chromomagnetic operator O_CM, which appears in the effective Hamiltonian describing DS=1 transitions in and beyond the Standard Model.
Having dimension 5, the chromomagnetic operator is characterized by a rich pattern of mixing with other operators of equal and lower dimensionality. We have computed the coefficients of the mixing with the various dimension 5...
Mr
Attila Nagy
(Humboldt University Berlin)
27/06/2014, 18:10
We investigate the impact of a $\lambda_6 \pi^6$ term included in a
chiral invariant lattice Higgs-Yukawa model. Such a term could emerge from BSM physics at some larger energy scale.
We map out the phase structure of the Higgs-Yukawa model with positive
$\lambda_6$ and negative quartic self coupling. To this
end, we evaluate the constraint effective potential in lattice perturbation...
Prof.
Massimo D'Elia
(University of Pisa & INFN)
28/06/2014, 08:30
Talk
Prof.
Tilo Wettig
(University of Regensburg)
28/06/2014, 09:00
Talk
I will give an overview of QPACE 2, which is a custom-designed machine based on Intel Xeon Phi processors, developed by Regensburg University in collaboration with Eurotech (Italy/Japan). I will also discuss our high-performance implementation of a domain-decomposition-based solver on the Xeon Phi and present benchmarks of its strong-scaling behavior.
Prof.
Masakiyo Kitazawa
(Osaka University)
28/06/2014, 09:30
We propose a novel method to define and calculate the
energy-momentum tensor (EMT) in lattice gauge theory on the basis of the
Yang-Mills gradient flow.
Using this method, we measure the thermodynamics of SU(3) gauge theoy on
fine
lattices with lattice size up to 64^3x18.
The numerical results with small lattice spacing confirm our previous
findings;
the expectation values of the EMT...
Prof.
Chris Sachrajda
(University of Southampton)
28/06/2014, 10:30
Talk
