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

TL;DR

This paper uses Bayesian Monte Carlo methods to analyze new experimental data from SeaQuest and STAR, improving understanding of the proton's antiquark sea and the -u asymmetry at high momentum fractions.

Contribution

It introduces a Bayesian Monte Carlo framework for global QCD analysis incorporating recent SeaQuest and STAR data, revealing significant constraints on the -u asymmetry.

Findings

SeaQuest data reduces uncertainty on /u ratio at high x

Results favor an enhanced  sea up to x a0d 0.4

Agreement with nonperturbative QCD calculations based on chiral symmetry

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.