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

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 $R_s=(s+\bar{s})/(\bar{u}+\bar{d})=\{0.72_{-0.34}^{+0.52},0.46_{-0.20}^{+0.30},0.32_{-0.15}^{+0.23}\}$ 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.

Comments: 40 pages, 11 figures, 14 tables, updated version. To appear in Phys. Rev. D