Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of the W→ℓν and Z→ℓℓ 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 1:00þ0:25 0:28 at absolute four-momentum transfer squared Q2 ¼ 1:9 GeV2 and x ¼ 0:023.