Title: Quasi-parton distribution functions: A study in the diquark spectator model

Abstract

A set of quasi-parton distribution functions (quasi-PDFs) have been recently proposed by Ji. Defined as the matrix elements of equal-time spatial correlations, they can be computed on the lattice and should reduce to the standard PDFs when the proton momentum P_z is very large. Since taking the P_z → ∞ limit is not feasible in lattice simulations, it is essential to provide guidance for what values of P_z the quasi-PDFs are good approximations of standard PDFs. Within the framework of the spectator diquark model, we evaluate both the up and down quarks' quasi-PDFs and standard PDFs for all leading-twist distributions (unpolarized distribution f₁, helicity distribution g₁, and transversity distribution h₁). We find that, for intermediate parton momentum fractions x, quasi-PDFs are good approximations to standard PDFs (within 20–30) when P_z ≳ 1.5–2 GeV. On the other hand, for large x ~ 1 much larger P_z > 4 GeV is necessary to obtain a satisfactory agreement between the two sets. We further test the Soffer positivity bound, and find that it does not hold in general for quasi-PDFs.

Authors:

Gamberg, Leonard; Kang, Zhong-Bo; Vitev, Ivan; Xing, Hongxi

Publication Date:

Wed Apr 01 00:00:00 EDT 2015

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Penn State Berks, Reading, PA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Laboratory Directed Research and Development (LDRD) Program

OSTI Identifier:

1198586

Alternate Identifier(s):

OSTI ID: 1200902; OSTI ID: 1906136

Grant/Contract Number:  

20130783PRD2; 20130019DR; FG02-07ER41460; AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Physics Letters. B

Additional Journal Information:

Journal Name: Physics Letters. B Journal Volume: 743 Journal Issue: C; Journal ID: ISSN 0370-2693

Publisher:

Elsevier

Country of Publication:

Netherlands

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Quantum chromodynamics, Parton distributions