We present the first direct lattice calculation of the isovector sea-quark parton distributions using the formalism developed recently by one of the authors. We use Nf=2+1+1 HISQ lattice gauge ensembles (generated by MILC Collaboration) and clover valence fermions with pion mass 310 MeV. We are able to obtain the qualitative features of the nucleon sea flavor structure even at this large pion mass: We observe violation of the Gottfried sum rule, indicating d(x)>u(x); the helicity distribution obeys Δu(x)>Δd(x), which is consistent with the STAR data at large and small leptonic pseudorapidity.
@article{arxiv.1402.1462,
title = {Flavor Structure of the Nucleon Sea from Lattice QCD},
author = {Huey-Wen Lin and Jiunn-Wei Chen and Saul D. Cohen and Xiangdong Ji},
journal= {arXiv preprint arXiv:1402.1462},
year = {2015}
}