Lattice QCD Constraints on the Parton Distribution Functions of ^{3}He.

William Detmold,Frank Winter,Marc Illa,David J Murphy,Patrick Oare,Phiala E Shanahan,Kostas Orginos,Michael L Wagman

doi:10.1103/physrevlett.126.202001

Abstract

The fraction of the longitudinal momentum of ^{3}He that is carried by the isovector combination of u and d quarks is determined using lattice QCD for the first time. The ratio of this combination to that in the constituent nucleons is found to be consistent with unity at the few-percent level from calculations with quark masses corresponding to m_{π}∼800 MeV. With a naive extrapolation to the physical quark masses, this constraint is consistent with, and more precise than, determinations from global nuclear parton distribution function fits through the nnnpdf framework. It is thus concretely demonstrated that lattice QCD calculations of light nuclei have imminent potential to enable more precise determinations of the u and d parton distributions in light nuclei and to reveal the QCD origins of the EMC effect.

Highlights

With a naive extrapolation to the physical quark masses, this constraint is consistent with, and more precise than, determinations from global nuclear parton distribution function fits through the nNNPDF framework
In terms of the parameters defined in that work, nuclear effects in the isovector momentum fraction are encapsulated in the low energy constant (LEC) α3;2 and nuclear factor G3ð3HeÞ; their product is bounded as α3;2G3ð3HeÞ 1⁄4 0.0018ð14Þ at μ 1⁄4 2 GeV from the numerical calculations presented here
The isovector momentum fractions determined here provide valuable information that is complementary to experimental constraints on the nuclear modification of parton distribution functions (PDFs); almost all information on the nuclear modification of partonic structure has been obtained for the ratio of isoscalar-corrected F2 structure functions of nuclei to that of the deuteron [3,5,6]

Summary

Introduction

With a naive extrapolation to the physical quark masses, this constraint is consistent with, and more precise than, determinations from global nuclear parton distribution function fits through the nNNPDF framework.

Results

Conclusion