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

We perform a global QCD analysis of unpolarized parton distribution functions (PDFs) in the proton, including new W + charm production data from p p 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 + s ¯) / (u ¯ + d ¯) = 0. 7 2 − 0. 34 + 0. 52, 0. 4 6 − 0. 20 + 0. 30, 0. 3 2 − 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 − s ¯, which is found to be consistent with zero in this range.