### 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 which 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 f_{1}, helicity distribution g_{1}, and transversity distribution h_{1}). 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.

Original language | English (US) |
---|---|

Pages (from-to) | 112-120 |

Number of pages | 9 |

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

Volume | 743 |

DOIs | |

State | Published - Apr 9 2015 |

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### All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics

### Cite this

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

*743*, 112-120. https://doi.org/10.1016/j.physletb.2015.02.021

}

*Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics*, vol. 743, pp. 112-120. https://doi.org/10.1016/j.physletb.2015.02.021

**Quasi-parton distribution functions : A study in the diquark spectator model.** / Gamberg, Leonard; Kang, Zhong Bo; Vitev, Ivan; Xing, Hongxi.

Research output: Contribution to journal › Article

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

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.

UR - http://www.scopus.com/inward/record.url?scp=84923320704&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84923320704&partnerID=8YFLogxK

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 -