LaMET 2021 Online

Session

Session II

7 Dec 2021, 10:25

Zoom

Conveners

Session II

• Peter Petreczky (BNL)

Session II

• David Richards (Jefferson Lab)

Session II

• Andreas Schaefer (Regensburg University)

9. The continuum and leading twist limits of pseudo-PDFs

Joseph Karpie

07/12/2021, 10:25

The continuum limit is a fundamental step when using a lattice regulator and necessary for any high precision calculation using lattice QCD. The matrix elements used in determining a PDF have two dimensionful parameters, compared to the 0 or 1 of most lattice calculations, which significantly complicates the continuum limit extrapolation. In this presentation, I will describe a method which...

18. Towards High-Precision Nucleon Parton Distributions via Distillation

Colin Egerer (Jefferson Lab)

07/12/2021, 10:50

We apply the Distillation spatial smearing program to the extraction of the
unpolarized isovector valence PDF of the nucleon using the pseudo-distribution formalism. The improved volume sampling and control of excited-states afforded by distillation leads to a dramatically improved determination of the requisite Ioffe-time Pseudo-distribution (pITD).
The valence PDF is extracted by analyzing...

24. Lattice Calculation of the Second Moment of the Pion Light-Cone Distribution Amplitude

Anthony Grebe

07/12/2021, 11:15

The pion light-cone distribution amplitude (LCDA) carries information about the momentum distribution of its quarks, which is an important input to various experiments. We present a proof-of-concept lattice calculation of the second Mellin moment of the pion LCDA as the first numerical implementation of the heavy-quark operator product expansion (HOPE) method. The resulting value for the...

25. Investigation of the fourth moment of the pion light-cone distribution amplitude

Robert Perry (National Yang Ming Chiao Tung University)

07/12/2021, 11:30

The light-cone distribution amplitude (LCDA) is a key object of interest in a range of high-energy, exclusive processes in QCD. In this talk, we describe the application of the heavy quark operator product expansion (HOPE) method to a preliminary study of the fourth Mellin moment of the pion LCDA. This constitutes the first study of the fourth moment from lattice QCD. We present an exploratory...

22. Global QCD Analysis of Pion Parton Distributions Including Lattice QCD Data

Patrick Barry

07/12/2021, 11:45

For the first time, we perform a fit of pion parton distribution functions (PDFs) to reduced pseudo Ioffe time distributions and current-current correlator "good lattice cross sections" generated from lattice QCD simultaneously with experimental data. We make use of the factorization formulas convoluting the matching coefficients with the valence quark distribution to fit to real components...

12. Polarized gluon pseudodistributions at short distances

Wayne Morris

08/12/2021, 10:35

We present the results that are necessary in the ongoing lattice calculations of the polarized gluon parton distribution functions within the pseudo-PDF approach. We give a classification of possible two-gluon correlator functions and identify those that contain the invariant amplitude determining the polarized gluon PDF in the light-cone $z^2 \to 0$ limit. One-loop calculations have been...

10. Gluon Parton Distribution of the Pion and Nucleon from Lattice QCD

Zhouyou Fan

08/12/2021, 10:55

We present the $x$-dependent nucleon and pion gluon distribution from lattice QCD using the pseudo-PDF approach, on lattice ensembles with $2+1+1$ flavors of highly improved staggered quarks (HISQ), generated by MILC Collaboration. We use clover fermions for the valence action and momentum smearing to achieve pion boost momentum up to 2.56~GeV on three lattice spacings $a\approx 0.9, 0.12$ and...

16. Gluon distributions of the nucleon from lattice QCD

Raza Sufian

08/12/2021, 11:15

We present lattice QCD calculation of unpolarized and polarized gluon Ioffe-time distributions using the pseudo-PDFs approach. We construct the nucleon interpolation fields using the distillation technique and smear the gauge fields using gradient flow. We calculate flow time-independent reduced Ioffe-time pseudo-distribution and from that, determine the unpolarized gluon PDF in the...

8. One-loop structure of parton distribution for the gluon condensate and "zero modes"

Shuai Zhao (Old Dominion University/Jefferson Lab)

08/12/2021, 11:40

We present the results for the one-loop corrections to the "gluon condensate" twist-4 PDF F(x), in particular, we give expression for the $gg$-part of its evolution kernel. To enforce strict compliance with the gauge invariance requirements, we have used on-shell states for external gluons and have obtained identical results both in Feynman and light-cone gauges. No "zero mode" terms were...

4. Disentangling Long and Short Distances in Momentum-Space TMDs

Zhiquan Sun

09/12/2021, 10:35

The extraction of nonperturbative TMD physics is made challenging by prescriptions that shield the Landau pole, which entangle long- and short-distance contributions in momentum space. The use of different prescriptions then makes the comparison of fit results for underlying nonperturbative contributions meaningless on their own. We propose a model-independent method to restrict...

21. x-dependence of transversity GPDs on the lattice

Aurora Scapellato

09/12/2021, 10:55

In this talk we present results for isovector transversity generalized parton distributions (GPDs) of the proton obtained within lattice QCD. We employ the quasi-distribution formalism, which relies on computations of nonlocal matrix elements of boosted hadron states. Large momentum effective theory (LaMET) is then used to match quasi- to light-cone GPDs.
Results are obtained on an...

20. First Lattice QCD Study of Proton Twist-3 GPDs

Jack Dodson

09/12/2021, 11:20

Calculating the x-dependence of PDFs and GPDs from lattice QCD has become feasible in the last few years due to novel approaches. In the work presented, we employ the quasi-distributions method, which relies on matrix elements of non-local operators, matched to the light-cone distributions using Large Momentum Effective Theory (LaMET). We focus on results for the first-ever lattice QCD...

23. QCD factorization for twist-3 quasi and pseudo-distributions

Yao Ji

09/12/2021, 11:40

In this talk, I will discuss our recent studies of the twist-3 nucleon parton distribution functions suitable for lattice simulations. The corresponding factorized expressions are derived in terms of the twist-two and twist-three collinear distributions to one-loop accuracy. We present the one-loop matching coefficient functions both in position space, as the factorization theorem for...

11. Approaching Continuum limits of Strange Parton Distribution Functions in Lattice QCD

Santanu Mondal (Michigan State University)

We present preliminary lattice QCD calculations of the unpolarized and polarized distributions of the strange quark using the LaMET method. We use three $N_f=2+1+1$ HISQ ensembles generated by MILC collaboration at lattice spacings $a \approx 0.09, 0.12 {~\rm and~} 0.15$ fm, and clover valence fermions with two valence pion masses: 310 and 690 MeV. We use momentum-smeared sources to improve...