[Hadstruct] [EXTERNAL] Re: Proposed abstracts for Lattice 2021

Thu Apr 29 19:40:14 EDT 2021

Hi everyone,

Thank you for sharing your abstracts. Only a couple of minor comments on some of them:

Colin: first, do you really mean "Expounding"? I usually take "expound (on)" to mean "explain" or "state in detail", but that doesn't seem to be the sense in which you're using it, because of the phrase that follows the comma. Second, I wonder whether "model independent" is going to inflame some people and it might be worth rephrasing that? Third, I think you can remove the last sentence completely.

Nikhil: I've been going backwards and forwards on "very crucial". I think just "crucial" is sufficient.

Raza: I think you can write just "gradient flow" instead of "gradient flow technique" to avoid repeating "technique" twice in quick succession.

Tanjib: I suggest some minor rewording:

We present our calculation of the unpolarized gluon parton distribution function (PDF) in the nucleon using the Pseudo-PDF technique on a $32^3 \times 64$
isotropic lattice with a pion mass of 358 MeV. The nucleon interpolating fields are constructed using distillation and we apply the sGEVP method

to calculate the gluonic matrix elements. We smear the gauge fields using the gradient flow to compute the flowed matrix elements and using the double ratio,
we calculate the flowed reduced Ioffe-time distribution (rITD). We extrapolate the results to the flow-time independent rITD and calculate the light-cone ITD
in the $\overline{MS}$ scheme, at the small z-separation limit, using an NLO matching formula. Finally, the gluon PDF is calculated from the light-cone ITD by
applying the appropriate kernel form.

It's great to see HadStruc providing so many abstracts!

Regards,
Chris

---

Chris Monahan
Pronouns: he/his
Assistant Professor
Department of Physics
William & Mary
757-221-2081
________________________________
From: Hadstruct <hadstruct-bounces at jlab.org> on behalf of Colin Egerer <cpegerer at email.wm.edu>
Sent: 29 April 2021 15:51
To: hadstruct at jlab.org <hadstruct at jlab.org>
Subject: Re: [Hadstruct] [EXTERNAL] Re: Proposed abstracts for Lattice 2021

Hello All,

Per Savva's suggestion, Christos and I spoke and amended our abstracts and titles to reflect sequential presentations.
Co-authors for all: Robert, ME, Christos, Kostas, David, Eloy and Savvas

Christos
Title: Towards High-Precision Nucleon Parton Distributions via Distillation - I

Abstract: We compute the unpolarized valence quark parton distribution function (PDF) from Lattice QCD, using a gauge ensemble of $N_f=2+1$ Wilson-Clover fermions with $m_\pi = 350$ MeV. Promising results from a second ensemble at the physical pion mass are also presented. We employ the pseudo-PDF formalism in combination with the distillation method for the first time, yielding a significantly improved statistical precision of the computed Ioffe-time distributions (ITDs) and resulting x-dependence over traditional methods for calculating matrix elements. We compare our extracted x-dependence of the nucleon valence PDF with phenomenology and other recent lattice evaluations.

Colin

Title: Towards High-Precision Nucleon Parton Distributions via Distillation - II

Abstract: The pseudo-distribution formalism is one such methodology capable of illuminating the collinear structure of hadrons from matrix elements of suitably constructed space-like operators calculated using lattice QCD. Expounding upon the unpolarized nucleon PDF calculation of the HadStruc collaboration, the improved statistical quality of the computed Ioffe-time pseudo-distributions opens the possiblity of rigorously quantifying systematics inherent to this calculation. A method to simultaneously extract the PDFs and capture and remove systematic effects is developed. This bolsters the prospect of a model-independent PDF extraction. Comparisons are made with contemporary results from the lattice community and an array of phenomenological determinations.

Comments are appreciated.

Thanks,

Colin

On Thu, Apr 29, 2021 at 2:07 PM Savvas Zafeiropoulos <savvaslz at gmail.com<mailto:savvaslz at gmail.com>> wrote:
Hey Christo and Colin,

Should you arrange for back to back talks? That would be better…And you should email the organisers to make sure that one of you is going to do the part A and the other the part B….

Best,
Savvas

On 29 Apr 2021, at 19:58, Christos Kallidonis <kallidoc at jlab.org<mailto:kallidoc at jlab.org>> wrote:

Hello all,

Here’s my contribution for the Lattice conference. It looks like mine and Colin’s abstract have quite an overlap, but we should be able to resolve this (perhaps by considering presenting GPDs as well?).

Co-Authors: Robert Edwards, Colin Egerer, Kostas Orginos, David Richards, Savvas Zafeiropoulos

Title: The nucleon valence quark distribution functions from Lattice QCD: An exploratory study of distillation in the pseudo-PDF framework

Abstract: We compute the unpolarized valence quark parton distribution function (PDF) from Lattice QCD, using a gauge ensemble of $N_f=2+1$ Wilson-Clover fermions with $m_\pi = 350$ MeV. Preliminary results from a second ensemble at the physical pion mass are also presented. We employ the pseudo-PDF formalism in combination with the distillation method for the first time, yielding a significantly improved statistical accuracy of the computed Ioffe-time distributions (ITDs) and resulting x-dependence over traditional methods for calculating matrix elements. We elaborate on the perturbative 1-loop evolution of the ITDs as well as a set of PDF parametrization schemes and discuss various systematics. We compare our extracted x-dependence of the nucleon valence PDF with phenomenology and with other recent Lattice QCD evaluations.

Any comments or suggestions are welcome.
Thanks.

Best,
Christos

On Apr 29, 2021, at 1:17 PM, Nikhil Karthik <nkarthik.work at gmail.com<mailto:nkarthik.work at gmail.com>> wrote:

Hi all,

Here is the transversity PDF abstract. Please let me know your suggestions, if any.

Title:  The transversity PDF of the nucleon using the pseudo-distribution approach

Abstract:
The transversity parton distribution function probes the x-dependent difference between quarks with their spins aligned and anti-aligned with the transverse polarization of the nucleon. The chiral-odd nature of the transversity makes it experimentally harder to extract than unpolarized distributions, thereby making the lattice determination very crucial.  In this talk, we will present results on the lattice computation of the nucleon transversity PDF using the distillation method and by employing the pseudo-distribution approach on an ensemble with the lattice spacing a=0.094 fm and 358 MeV pion mass.

Thank you.
Nikhil

On Thu, Apr 29, 2021 at 12:35 PM Colin Egerer <cpegerer at email.wm.edu<mailto:cpegerer at email.wm.edu>> wrote:
Hi All,

I'll add one more in this list of abstracts. Should I be unable to present during the meeting, I will arrange with Christos on how to best present our findings.
As for co-authors, I have: Christos, Kostas, Anatoly, David, Eloy and Savvas.

Title:
Towards High-Precision Parton Distributions via Distillation

Abstract:
The pseudo-distribution formalism is one such methodology capable of illuminating the collinear structure of hadrons from matrix elements of suitably constructed space-like operators calculated using lattice QCD. Leveraging the distillation spatial smearing program, we extract the unpolarized isovector valence and plus quark PDFs of the nucleon via a direct 1-loop matching of the computed Ioffe-time pseudo-distribution and PDF parameterizations. The tempering of excited-states and improved volume sampling afforded by distillation lead to high quality Ioffe-time pseudo-distributions and their $\overline{\text{MS}}$ light-cone counterparts. This bolsters confidence in the extracted PDFs, and allows for a rigorous quantitative accounting of lattice systematics. The PDFs we determine are compared with contemporary results from the lattice community and an array of phenomenological determinations.

Thanks,
Colin

On Thu, Apr 29, 2021 at 12:25 PM Raza Sufian <sufian at jlab.org<mailto:sufian at jlab.org>> wrote:
Dear All,

Below please find my abstract. Since I do not know yet whether matrix elements of pseudo-PDF or LCS or both can have signal, I do not mention any formalism and just say Ioffe-time distribution.

Title: Towards determining polarized gluon distribution from lattice QCD

Abstract: We present a calculation of lattice QCD non-local matrix elements that can be used to determine polarized gluon Ioffe-time distribution and the corresponding parton distribution function using QCD short distance factorization. We construct the nucleon interpolation fields using the distillation technique and flow the gauge fields using the gradient flow technique. Our calculation is performed on a $32^3 \times 64$ isotropic lattice with a pion mass of 358 MeV.

Thank you.
-Raza

On Apr 29, 2021, at 11:27 AM, Wayne Morris <wmorr001 at odu.edu<mailto:wmorr001 at odu.edu>> wrote:

Unpolarized and polarized gluon pseudo-distributions at short distances: Forward case

We present the results that are necessary in the ongoing lattice calculations of the unpolarized and polarized gluon parton distribution functions (PDFs) 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 gluon PDF in the light-cone $z^2\to 0$ limit. One-loop calculations have been performed in the coordinate representation and in an explicitly gauge-invariant form. We made an effort to separate ultraviolet (UV) and infrared (IR) sources of the $\ln \left(-z^2\right) $-dependence at short distances $z^2$. The UV terms cancel in the reduced Ioffe-time distribution (ITD), and we obtain the matching relation between the reduced ITD and the light-cone ITD. Using a kernel form, we get a direct connection between lattice data for the reduced ITD and the normalized gluon PDF.

On Thu, Apr 29, 2021 at 11:09 AM Md Tanjib Atique Khan <mkhan01 at email.wm.edu<mailto:mkhan01 at email.wm.edu>> wrote:
Dear all,

Here is my abstract for Lattice21.

Title: Calculation of the Gluon PDF using Pseudo-PDF technique

Abstract:

We present our calculation of the unpolarized gluon parton distribution function (PDF) in the nucleon using Pseudo-PDF technique on a $32^3 \times 64$
isotropic lattice with a pion mass of 358 MeV. The nucleon interpolating fields are constructed using the distillation method while the sGEVP method is
used to calculate the gluonic matrix elements. We implement the gradient-flow technique to compute the flowed matrix elements and using the double ratio,
calculate the flowed reduced Ioffe-time distribution (rITD). We extrapolate the results to the flow-time independent rITD and calculate the light-cone ITD
in $\overline{MS}$ scheme, at the small z-separation limit, using NLO matching formula. Finally, the gluon PDF is calculated from the light-cone ITD by
applying appropriate kernel form.

Thanks,

Tanjib

On Wed, Apr 28, 2021 at 5:55 PM Savvas Zafeiropoulos <savvaslz at gmail.com<mailto:savvaslz at gmail.com>> wrote:
Dear All,

here is my abstract and title for lattice 2021

Progress on the extraction of parton distributions from Ioffe time distributions

The light-cone definition of Parton Distribution Functions (PDFs) does not allow for a direct ab initio determination employing methods of Lattice QCD simulations that naturally take place in Euclidean spacetime. In this presentation we focus on pseudo-PDFs where the starting point is the equal time hadronic matrix element with the quark and anti-quark fields separated by a finite distance. We focus on Ioffe-time distributions, which are functions of the Ioffe-time ν, and can be understood as the Fourier transforms of parton distribution functions with respect to the momentum fraction variable x. We present lattice results for the case of the nucleon addressing the physical point and continuum extrapolations. We also incorporate our lattice data in the NNPDF framework treating them on the same footing as experimental data and discuss in detail the different sources of systematics in the determination of the non-singlet PDFs.

Since I am going to present results from three published papers all the authors of those papers will be contributors for my talk in the indico website.
If anyone has a suggestion/correction etc please let me know!

Best,
Savvas

On Wed, Apr 28, 2021 at 3:55 PM Raza Sufian <sufian at jlab.org<mailto:sufian at jlab.org>> wrote:
Dear All,

Below please find the proposed abstracts for the Lattice 2021 conference. The deadline for abstract submission is on Friday, April 30. Please try to circulate your abstracts sometime tomorrow for comments. Please let us know if I forgot to list any other proposed abstract.

CK: Nucleon valence distribution using distillation

SZ: Nucleon valence distribution (continuum limit, physical point extrapolation + NNPDF analysis)

TK: Unpolarized gluon distribution

JK: RBC/UKQCD

NK: Transversity

RSS: Polarized gluon distribution

WM: Perturbative matching for …

TBD:

Patrick Barry

CE

Thank you.
-Raza
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