کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1849093 | 1528813 | 2015 | 9 صفحه PDF | دانلود رایگان |
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 PzPz is very large. Since taking the Pz→∞Pz→∞ limit is not feasible in lattice simulations, it is essential to provide guidance for which values of PzPz 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 f1f1, helicity distribution g1g1, and transversity distribution h1h1). 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 GeVPz≳1.5–2 GeV. On the other hand, for large x∼1x∼1 much larger Pz>4 GeVPz>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.
Journal: Physics Letters B - Volume 743, 9 April 2015, Pages 112–120