Bayesian Monte Carlo extraction of the sea asymmetry with SeaQuest and STAR data

We perform a global QCD analysis of unpolarized parton distributions within a Bayesian Monte Carlo framework, including the new W-lepton production data from the STAR Collaboration at RHIC and Drell-Yan dimuon data from the SeaQuest experiment at Fermilab. We assess the impact of these two new measurements on the light antiquark sea in the proton and the d̄-ū asymmetry in particular. The SeaQuest data are found to significantly reduce the uncertainty on the d̄/ū ratio at large parton momentum fractions x, strongly favoring an enhanced d̄ sea up to x≈0.4, in general agreement with nonperturbative calculations based on chiral symmetry breaking in QCD.