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

Abstract

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 di-muon 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 $\bar{d}-\bar{u}$ asymmetry in particular. The SeaQuest data are found to significantly reduce the uncertainty on the $\bar{d}/\bar{u}$ ratio at large parton momentum fractions $x$, strongly favoring an enhanced $\bar{d}$ sea up to $x\approx 0.4$, in general agreement with nonperturbative calculations based on chiral symmetry breaking in QCD.

10 pages, 8 figures

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• Generalized parton distributions at zero skewness
• On the determination of uncertainties in parton densities
• Measurement of flavor asymmetry of light-quark sea in the proton with Drell-Yan dimuon production in $p+p$ and $p+d$ collisions at 120 GeV
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• Nucleon form factors and parton distributions in nonlocal chiral effective theory
• Pions in Proton Structure and Everywhere Else
• Octet and decuplet baryon $\sigma$-terms and mass decompositions
• Collinear Factorization at sub-asymptotic kinematics and validation in a diquark spectator model