Iso-spin asymmetry of quark distributions and implications for single top-quark production at the LHC

TL;DR

This paper refines the understanding of up- and down-quark distributions in the proton using recent collider data, revealing a non-zero sea asymmetry at small x and providing predictions for single top-quark production at the LHC.

Contribution

It introduces an improved global fit of parton distribution functions incorporating recent data, highlighting a non-zero sea asymmetry at small x and offering precise predictions for top-quark production.

Findings

Evidence for non-zero sea asymmetry at small x

Consistent parton distribution functions with recent data

Predictions for single top-quark production at the LHC

Abstract

We present an improved determination of the up- and down-quark distributions in the proton using recent data on charged lepton asymmetries from $W^\pm$ gauge-boson production at the LHC and Tevatron. The analysis is performed in the framework of a global fit of parton distribution functions. The fit results are consistent with a non-zero iso-spin asymmetry of the sea, $x(\bar d - \bar u)$, at small values of Bjorken $x\sim 10^{-4}$ indicating a delayed onset of the Regge asymptotics of a vanishing $(\bar d - \bar u)$-asymmetry at small-$x$. We compare with up- and down-quark distributions available in the literature and provide accurate predictions for the production of single top-quarks at the LHC, a process which can serve as a standard candle for the light quark flavor content of the proton.