Determination of the strange-quark density of the proton from ATLAS measurements of the W→lν and Z→l cross sections

A QCD analysis is reported of ATLAS data on inclusive W± and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x∼0.01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1.00-0.28+0.25 at absolute four-momentum transfer squared Q2=1.9  GeV2 and x=0.023.