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Kim Maltman
(York University, Toronto)
23/06/2014, 14:15
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...
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Dr
Anthony Francis
(Helmholtz-Institut Mainz)
23/06/2014, 14:35
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...
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Ms
Vera Guelpers
(University of Mainz)
23/06/2014, 14:55
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...
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Ms
Bipasha Chakraborty
(SUPA, School of Physics and Astronomy, University of Glasgow)
23/06/2014, 15:15
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 Padรฉ 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...
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Mr
Luchang Jin
(Columbia University)
23/06/2014, 15:35
The anomalous magnetic moment of muon, g-2, is a very precisely
measured quantity. However, the current measurement disgrees with
standard model by about 3ฯ. 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...
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Mrs
Ekaterina Mastropas
(College of William and Mary)
23/06/2014, 16:30
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...
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Prof.
Brian Tiburzi
(City College of New York)
23/06/2014, 16:50
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...
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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.
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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...
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Mr
Christian Wiese
(DESY, Zeuthen)
24/06/2014, 14:35
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.
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Prof.
Gunnar Bali
(University of Regensburg)
24/06/2014, 14:55
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.
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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...
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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...
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Dr
Stefan Meinel
(Massachusetts Institute of Technology)
24/06/2014, 16:30
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...
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Dr
Alejandro Vaquero
(The Cyprus Institute)
24/06/2014, 16:50
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.
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Dr
Boram Yoon
(Los Alamos National Laboratory)
24/06/2014, 17:10
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...
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Mingyang Sun
(University of Kentucky)
24/06/2014, 17:30
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...
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Dr
Christian Torrero
(Centre de Physique Thรฉorique (CPT), Aix-Marseille Universitรฉ)
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...
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Dr
Georg von Hippel
(University of Mainz)
25/06/2014, 11:10
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...
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Dr
Giannis Koutsou
(The Cyprus Institute)
25/06/2014, 11:30
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...
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Dr
Shigemi Ohta
(Institute of Particle and Nuclear Physics, KEK)
25/06/2014, 11:50
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.ย ย The reports will be based mostly on the RBC+UKQCD Iwasaki+DSDR ensemble at pion mass of 170 MeV. ย The vector charge, axial charge, quark momentum and helicity fractions, and transversity are discussed. ย No autocorrelation issue...
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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 =...
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Prof.
Constantia Alexandrou
(University of Cyprus)
25/06/2014, 12:30
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.
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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...
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Mr
Michael Lujan
(The George Washington University)
26/06/2014, 14:15
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...
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Dr
Walter Freeman
(George Washington University)
26/06/2014, 14:35
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...
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Dr
JONG-WAN LEE
(City College of New York)
26/06/2014, 14:55
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...
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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...
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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...
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Mr
Christian Shultz
(Old Dominion University)
26/06/2014, 15:55
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...
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Mr
Benjamin Owen
(University of Adelaide)
26/06/2014, 16:15
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....
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Marina Marinkovic
(University of Southampton)
27/06/2014, 14:15
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.
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Mr
Rehan MALAK
(Mr)
27/06/2014, 14:35
For the Budapest-Marseille-Wuppertal collaboration.
We present preliminary lattice QCD results for the leading-order hadronic contribution to the muon anomalous magnetic moment. Computations are based on 2+1 flavour simulations with HEX-smeared clover fermions and pion masses down to its physical value. Besides the traditional approach, several methods implementing derivatives of the...
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Mr
Hanno Horch
(University of Mainz)
27/06/2014, 14:55
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...
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Gregorio Herdoiza
(KPH Mainz and IFT Madrid)
27/06/2014, 15:15
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...
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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.
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Dr
James Zanotti
(University of Adelaide)
27/06/2014, 16:30
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...
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Raza Sufian
(University of kentucky)
27/06/2014, 16:50
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...
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Michael Engelhardt
(New Mexico State University)
27/06/2014, 17:10
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...
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Jonathan Flynn
(University of Southampton)
27/06/2014, 17:30
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...
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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...
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Michael G Endres
(MIT)
27/06/2014, 18:10
Numerical studies of quantum theories usually rely upon an accurate determination of stochastically estimated correlation functions in order to extract information about the spectrum of the theory and matrix elements of operators. The reliable determination of such correlators is often hampered by an exponential degradation of signal/noise at late time separations. I will demonstrate that it...
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