Conveners
Structure function and parton densities: Updates of global PDF analyses (I)
- Benjamin Nachman
- Katarzyna Wichmann (DESY, Hamburg)
- Maria Zurita (University of Regensburg)
Structure function and parton densities: PDFs from Lattice QCD
- Maria Zurita (University of Regensburg)
- Benjamin Nachman
- Katarzyna Wichmann (DESY, Hamburg)
Structure function and parton densities: Jets & PDFs
- Benjamin Nachman
- Katarzyna Wichmann (DESY, Hamburg)
- Maria Zurita (University of Regensburg)
Structure function and parton densities: DIS (I)
- Katarzyna Wichmann (DESY, Hamburg)
- Maria Zurita (University of Regensburg)
- Benjamin Nachman
Structure function and parton densities: Updates of global PDF analyses (II)
- Katarzyna Wichmann (DESY, Hamburg)
- Benjamin Nachman
- Maria Zurita (University of Regensburg)
Structure function and parton densities: Nuclear PDFs
- Benjamin Nachman
- Maria Zurita (University of Regensburg)
- Katarzyna Wichmann (DESY, Hamburg)
Structure function and parton densities: DIS (II)
- Katarzyna Wichmann (DESY, Hamburg)
- Benjamin Nachman
- Maria Zurita (University of Regensburg)
Structure function and parton densities: EW bosons and Top quark
- Katarzyna Wichmann (DESY, Hamburg)
- Maria Zurita (University of Regensburg)
- Benjamin Nachman
Structure function and parton densities: TMDs
- Benjamin Nachman
- Maria Zurita (University of Regensburg)
- Katarzyna Wichmann (DESY, Hamburg)
We report an update of the ABM PDF fit with a focus on the impact of recent data from the LHC, in particular the ones on W- and Z-boson and not-resonant lepton pair production. Different
approaches to generation of the nucleon photon distribution are considered within the ABM framework and compared to the relevant data. The updated values of strong coupling constant and the heavy quark...
The final CT18 global analysis released at the end of 2019 is based on the most complete combination of LHC and non-LHC experimental measurements to date. We discuss implications of this expansive data set for the understanding of the unpolarized PDFs and introduce several alternative fits to explore a number of critical features: the PDF pulls of the high-precision ATLAS 7 TeV W/Z data...
I will give an update on the latest major PDF update with the MSTW/MMHT
framework. The update includes the effects of numerous new data sets, mainly
from the LHC. This includes vector boson production, differential in rapidity,
mass or p_T, or usually some combination. We also include new jet data and
inclusive and differential top pair producation data. There have also been...
The transverse momentum dependent parton distribution functions (TMDPDFs) measure the transverse momentum of partons in a fast moving hadron, and is an important observable for the Electron-Ion Collider. The energy evolution of TMDPDFs is given by the Collins-Soper (CS) anomalous dimension, or the CS kernel, which is essential to the fitting of TMDPDFs from global cross section data at...
We present results on the nucleon valence quark distribution extracted from Lattice QCD simulations, using a gauge ensemble of $N_f=2+1$ Wilson-Clover fermions with a pion mass of $m_\pi = 350$ MeV and lattice spacing of about $a=0.093$ fm. We obtain reduced Ioffe Time Distributions (rITDs) by computing appropriate matrix elements on the lattice, and elaborate on the extraction of the desired...
In recent years, parton distributions have been calculated from ab initio QCD using non-perturbative lattice field theory. In this presentation, I focus on a Lorentz invariant generalization of the Ioffe time distribution which can be calculated directly on the Lattice. Just like experimental cross sections, these matrix elements can be factorized into the PDF. I present our latest results for...
An understanding of the partonic structure of hadrons is an essential ingredient in making precise predictions and measurements of hadronic cross-sections and various Standard, and Beyond Standard, Model parameters. Direct first-principles calculations of parton distribution functions (PDFs) via lattice QCD (LQCD) were historically limited to the lowest few moments, principally due to the...
We present our high-statistics lattice QCD determination of the valence PDF of 300 MeV pion using the quasi- and pseudo-PDF (reduced Ioffe-time distribution) formalisms. For the first time in such lattice computations of PDF, we employ two different fine lattice spacings of 0.04 and 0.06 fm, which thereby enables us to use pion boosted to large spatial momenta up to 1.92 GeV that is essential...
We present new lattice QCD calculations for unpolarized and helicity isovector parton distribution functions of nucleons. Lattice QCD calculations were carried out within the framework of large momentum effective theory (LaMET), using a superfine lattice spacing 0.042 fm and boosted nucleons with momenta up to 2.31 GeV. We compare our QCD-based results with those obtained from global fits, and...
We present the first attempt to access the x-dependence of the gluon polarized and strange parton distribution functions (PDFs) from lattice calculations, using large-momentum effective theory (LaMET). LaMET methods have been applied to a wide variety of isovector nucleon distributions and valence pion distributions. However, the polarized gluon and strange-quark distributions have not yet...
Lattice QCD and global PDF analyses have both made significant strides in recent years. Much of this progress owes to the growing availability of computational resources as well as steady theoretical advances in lattice gauge theory and perturbative QCD. In this context, it is increasingly suggested that the output of lattice QCD calculations could serve as important input to global fits for...
Jets, clusters of collimated particles, produced from parton scatterings in high energy
proton-proton collisions are an effective tool to study the internal proton structure. At center of mass
energies of $\sqrt{s} = $ 200 and 510 GeV, jet production is dominated by the quark-gluon, $qg$ and
gluon-gluon, $gg$, scattering processes. The STAR experiment at the Relativistic Heavy Ion...
Jet measurements play an essential role in PDF fits and the available measurements will be briefly summarized. The primary experimental uncertainties in these measurements are the knowledge of the jet energy scale and resolution. The analyses used to evaluate these uncertainties will be described as well as how they are combined to form the set of uncertainties that dominate these...
We present fits to determine parton distribution functions (PDFs) using inclusive W/Z-boson and W+jets measurements from the ATLAS experiment at the LHC. The ATLAS measurements are used in combination with deep-inelastic scattering data from HERA. If available, we also present the results of PDF fits that use Z+jets measurements from ATLAS in addition to the measurements listed above. The...
The associated production of vector bosons V (W, Z or gamma) and jets originating from heavy-flavour (c or b) quarks is a large background source in measurements of other standard model processes, Higgs boson studies, and many searches for physics beyond the SM. The study of events with a vector boson accompanied by heavy-flavour jets is crucial to refine the theoretical calculations in...
Jet production measurements have represented one of the cornerstones of global PDF analyses since the early days of the Tevatron. Here we critically revisit the impact of jet production measurements from the LHC at 7 and 8 TeV within a global PDF fit by exploiting recent progress in NNLO QCD calculations. For the first time, we demonstrate that dijet production measurements can be successfully...
Proton parton distribution functions (PDFs) are poorly constrained by existing data for Bjorken $x$ larger than 0.6, and the PDFs extracted from global fits differ considerably from each other. A technique for comparing predictions based on different PDF sets to observed event numbers is presented. It is applied to compare predictions from the most commonly used PDFs to published ZEUS data at...
The CJ15 global next-to-leading-order analysis of PDFs utilized, amongst others, inclusive and tagged DIS structure function data from Jefferson Lab (JLab) and high-precision charged lepton and W-boson asymmetry data from Fermilab. As an extension to the CJ15 analysis, new JLab Hall A and C data from experiments jl00106F2, e06009d, e99118, jlcee96 and e03103, and Hall B data from the BONuS and...
Using data from a recent reanalysis of neutron structure functions extracted from inclusive proton and deuteron DIS, we re-examine the constraints on the shape of the $\bar d − \bar u$ asymmetry in the proton at large parton momentum fractions $x$. A global analysis of the proton–neutron structure function difference from BCDMS, NMC, SLAC and Jefferson Lab DIS measurements, and of Fermilab...
We formulate a general approach to the inclusion of theoretical uncertainties, specifically those related to the missing higher order uncertainty (MHOU), in the determination of parton distribution functions (PDFs). We demonstrate how, under quite generic assumptions, theory uncertainties can be included as an extra contribution to the covariance matrix when determining PDFs from data. We...
We present a new, simultaneous extraction of spin-averaged and spin-dependent PDFs within a multi-step Monte Carlo analysis. Utilizing data from inclusive jet production in unpolarized and polarized proton-proton and proton-antiproton collisions, we determine for the first time the spin-dependent gluon distribution, $\Delta g(x)$, at the same time as the unpolarized gluon PDF, $g(x)$....
We present a comprehensive review of existing Monte Carlo methods used in global QCD analyses of parton distribution functions. We critically examine the interpretability of uncertainties on extracted parton distributions against nested sampling and the more traditional Hessian approach. We show how in some cases the inclusion of resampling, partition, and cross-validation of the data can...
I present ongoing progress towards a new global PDF analysis from the NNPDF Collaboration: NNPDF4.0. As compared to its predecessor, NNPDF3.1, it contains several improvements from the theory input, dataset, and methodology points of view. NNPDF4.0 includes a large number of new experimental measurements from HERA, ATLAS, CMS, and LHCb, among others for the first time the HERA jet...
We present recent results from the xFitter project: an open-source
software framework for the determination of PDFs and the analysis of
QCD physics. xFitter has been used for a variety of LHC studies
including the measurement of the strange PDF, which we briefly
summarize. Additionally, charged current DIS charm production provides
a complementary perspective on s(x). We make use of the...
A number of PDF sets have either recently been produced (CT18), or will be coming out in the near future (from MMHT, NNPDF), utilizing high statistics, high precision data from the LHC. In 2015, an intense year-long benchmarking exercise was carried out among the global PDFs then available (CT14, MMHT2014, NNPDF3.0). This exercise allowed a better understanding of the relative influence of the...
The lack of a neutron target has resulted in a decades-long effort to understand the free neutron structure in order to test SU(6) symmetry breaking mechanisms. Approaches to address this open question traditionally extract the free neutron structure from proton + deuterium DIS data (and various other reactions such as jet production or W charge asymmetries).
Here we present a novel...
In the global analysis of nuclear Parton Distribution Functions
(nPDFs), one of the major sources of debate is how to include the
neutrino Deep Inelastic Scattering (DIS) data. The controversy comes
from the precise NuTeV neutrino DIS data which might indicate an
incompatibility with neutral current charged lepton DIS data. The
compatibility of NuTeV data was studied independently by...
We report on our progress of including the latest LHC p-Pb measurements on W$^\pm$, dijet, and D-meson production into the EPPS analysis of nuclear PDFs. The new data are observed to set strong constraints particularly on the gluons across a wide range in the momentum fraction $x$.
What new tools will we need for determining nuclear PDFs
at the HL-LHC, LHeC, and EIC in the next decade?
Current W/Z data from LHC is challenging our preconceptions
of the strange PDF. New hi-x data at low-Q from JLab push us
into the region of higher-twist and non-perturbative effects.
We provide an update of some nCTEQ progress in these areas,
and look ahead to characterize the impact...
The nCTEQ15 fit of nuclear Parton Distribution Functions (nPDFs)
includes data on Deep Inelastic Scattering (DIS), Drell-Yan (DY) and
single-inclusive pion production. In preparation for the upcoming
nCTEQ nPDF update, we present an analysis assessing the impact of
additional single-inclusive hadron production data in a nCTEQ15-like
fit. Specifically we look at pion production data from...
Resolving the quark and gluon structure of nuclei has been a crucial aim of the QCD physics community since the discovery of the EMC effect. Such information is given by the nuclear parton distribution functions (nPDFs), which describe the collinear momentum substructure of nucleons bound within nuclei and are accessed via global QCD analyses of lepton-nucleus and hadron-nucleus measurements....
We outline a strategy to compute deeply inelastic scattering structure functions using a hybrid quantum computer [1]. Our approach takes advantage of the representation of the fermion determinant in the QCD path integral as a quantum mechanical path integral over 0+1-dimensional fermionic and bosonic worldlines [2]. The proper time evolution of these worldlines can be determined on a quantum...
The CJ (CTEQ-Jefferson Lab) Collaboration provides a global fit of parton distribution functions (PDFs) with a special emphasis on the large x region. The latest fit (CJ15) implemented deuteron nuclear corrections at the parton level, and included data that were sensitive specifically to the neutron. These nuclear corrections allow for a calculation of the F2 structure functions of the proton,...
We analyze within the JAM framework the impact on unpolarized parton distributions of heavy-flavor production measurements in deep inelastic scattering. In particular, we investigate the recent combined results of inclusive and heavy-flavor production cross sections at HERA, which impose additional constraints on the gluon and the sea-quark distributions at low $x$.
We present our study of proton structure functions in view of the CLAS12 experiments planned in the near future, which are to study electron scattering observables at a wide $Q^2$ range and with high precision in x. CLAS experiments have achieved major advances in the study of the $N^∗$ region of the electroproduction spectrum, and the data on electrocouplings of the many baryon resonances in...
Following our recent Monte Carlo determination of the pion’s PDFs from Drell-Yan (DY) and leading neutron electroproduction data, we extend the analysis by including effects from threshold resummation. At higher orders in the strong coupling, $\alpha_S$, large logarithmic corrections due to soft gluon emissions become important in the $q\bar{q}$ channel near threshold, which can be summed over...
Measurements of the total and differential top-quark pair production cross sections in proton- proton collisions at 13 TeV with the ATLAS detector at the Large Hadron Collider are presented. The inclusive measurement reaches a precision of 2.4 %, well below the uncertainty of predictions at next-to-next-to-leading order in QCD. The measurement is performed in the di-lepton channel, requiring a...
We discuss the impact of top-quark pair production data on the CT18 PDFs family.
In particular, we discuss the individual impacts of differential ttbar cross section measurements at 8 TeV collision energy from CMS and ATLAS which have been analyzed using different statistical frameworks (ePump and PDFSense) to assess their impact on PDFs before the global fit. We discuss tensions between...
The differential cross section and charge asymmetry for inclusive W boson production at sqrt{s} = 13 TeV is measured for the two transverse polarization states as a function of the W boson absolute rapidity. The measurement uses events in which a W boson decays to either an electron or a muon and a neutrino. The data sample of proton-proton collisions recorded with the CMS detector at the LHC...
Over the past several years, parton distribution functions (PDFs) have become more precise. However there are still kinematic regions where more data are needed to help constrain global PDF extractions, such as the ratio of the sea quark distributions $\bar{d}$/$\bar{u}$ near the valence region. Furthermore, current measurements appear to suggest different high-$x$ behaviors of this ratio. The...
High-energy neutrinos represent a key pillar of multi-messenger astronomy and offer significant opportunities to advance fundamental physics. The interpretation of the results from high-energy neutrino detection experiments requires a good understanding of the attenuation processes that they undergo as they travel through the Earth. Here we present a novel framework, NuPropEarth, to evaluate...
The differential cross section measurements of the production of a pair of opposite-charged leptons as a function of pt and phi* in various bins of its invariant mass M are presented. The results are obtained using proton-proton collision data recorded with the CMS detector at the LHC. Measurements are also compared to state-of-the-art generators as well as TMD based predictions.
The leading-twist azimuthal asymmetries in the pion induced Drell-Yan process in the COMPASS kinematics are calculated considering any polarization of the proton target. The calculations are performed at tree level in the framework of TMD factorization using the predictions from the light front constituent model. The results are compared to the available COMPASS data, and predictions for not...
Transverse momentum dependent (TMD) parton distributions enter QCD factorisation formulas which include resummation and nonperturbative contributions to non-inclusive collider observables such as Drell-Yan differential cross sections. Recently, a parton branching (PB) formalism has been proposed for the evolution of TMDs, given in terms of Sudakov form factors and splitting functions. This...
We compute DIS structure functions using off-shell matrix elements based on kT-factorization. The obtained results are used together with parton branching evolution and HERA data in order to fit unintegrated (transverse momentum dependent) parton distributions. This allows us to have a consistent framework where off-shellness of initial partons is treated both in parton evolution and in matrix...
We present a new determination of Transverse Momentum Dependent (TMD) parton distributions obtained with the Parton Branching method. The PB TMDs are extracted from fits to precision DIS data using DGLAP splitting functions at leading and higher order.
In addition the fit sensitivity to dynamical resolution scales on TMD evolution in different kinematical region of x and Q2 will be investigated.
