Strangeness in the proton from W+charm production and SIDIS data

TL;DR

This paper presents a comprehensive QCD analysis incorporating new LHC and SIDIS data to better constrain the strange quark distribution in the proton, reducing uncertainties and confirming the symmetry between strange and anti-strange quarks.

Contribution

It introduces a novel global fit that includes recent W+charm and SIDIS data, significantly improving the precision of the strange quark PDF in the proton.

Findings

Uncertainty on strange quark distribution is reduced over 0.01 < x < 0.3.

Strange to nonstrange sea quark ratio R_s is quantified at multiple x values.

Strange asymmetry s - s̄ is consistent with zero within uncertainties.

Abstract

We perform a global QCD analysis of unpolarized parton distribution functions (PDFs) in the proton, including new $W +$\,charm production data from $pp$ collisions at the LHC and semi-inclusive pion and kaon production data in lepton-nucleon deep-inelastic scattering, both of which have been suggested for constraining the strange quark PDF. Compared with a baseline global fit that does not include these datasets, the new analysis reduces the uncertainty on the strange quark distribution over the range $0.01 < x < 0.3$, and provides a consistent description of processes sensitive to strangeness in the proton. Including the new datasets, the ratio of strange to nonstrange sea quark distributions is $R_s = (s+\bar s)/(\bar u+\bar d) = \{0.72^{+0.52}_{-0.34},\, 0.46^{+0.30}_{-0.20},\, 0.32^{+0.23}_{-0.15}\}$ for $x = \{ 0.01, 0.04, 0.1 \}$ at $Q^2 = 4$~GeV$^2$. The data place more stringent constraints on the strange asymmetry $s-\bar s$, which is found to be consistent with zero in this range.