TY - JOUR

T1 - Quasi-parton distribution functions

T2 - A study in the diquark spectator model

AU - Gamberg, Leonard

AU - Kang, Zhong Bo

AU - Vitev, Ivan

AU - Xing, Hongxi

N1 - Funding Information:
This work is supported by the U.S. Department of Energy under Contract Nos. DE-FG02-07ER41460 (L.G.) and DE-AC02-05CH11231 (Z.K., I.V. and H.X.), and in part by the LDRD program at LANL under grant numbers, 20130783PRD2 and 20130019DR .

PY - 2015/4/9

Y1 - 2015/4/9

N2 - 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 Pz is very large. Since taking the Pz→∞ limit is not feasible in lattice simulations, it is essential to provide guidance for which values of Pz 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 Pz≥1.5-2 GeV. On the other hand, for large x~1 much larger Pz>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.

AB - 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 Pz is very large. Since taking the Pz→∞ limit is not feasible in lattice simulations, it is essential to provide guidance for which values of Pz 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 Pz≥1.5-2 GeV. On the other hand, for large x~1 much larger Pz>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.

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U2 - 10.1016/j.physletb.2015.02.021

DO - 10.1016/j.physletb.2015.02.021

M3 - Article

AN - SCOPUS:84923320704

VL - 743

SP - 112

EP - 120

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

SN - 0370-2693

ER -