Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of theW→ℓνandZ→ℓℓCross Sections

Abstract

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 Q(2)=1.9 GeV(2) and x=0.023.

Progress in the Determination of the Partonic Structure of the Proton

“…It has been argued [145] that a fit only to inclusive W ± and Z differential cross sections [118], combined with inclusive DIS data from HERA, can significantly constrain the strange content of the proton, finding apparently no strange suppression, contrary to previous determinations from CCFR/NuTeV dimuon cross sections (νN → µµX). However, these conclusions are weakened in a similar NNPDF study using a more flexible parametrization form [111], or alternatively by incorporating a suitable tolerance [98], and it seems that present-day LHC W production data only have a very minor impact on strangeness, but this is again likely to change in the near future.…”

Reevaluation of the parton distribution of strange quarks in the nucleon

“…The parton distribution functions (PDFs) of the strange quarks in the nucleon describe important features of the structure of the quark sea and constrain models of its origin [1][2][3][4]. In addition, the strangeness content of the nucleon is of interest because of its impact on calculations of shortdistance processes at high energies [5] and also in view of recent ATLAS results [6], which suggest that at small x it could be substantially larger than previously assumed. In 2008 HERMES published the results of the extraction of the momentum and helicity density distributions of the strange sea in the nucleon from charged-kaon production in deep-inelastic scattering (DIS) on the deuteron [7].…”

Simultaneous measurements of thett¯,W+W−, andAad1, Kupčo2, Davison3 et al. 2015Phys. Rev. DSelf Cite

“…for the region excluding electrons or muons from tau-lepton decays. Theoretical predictions were calculated for the following PDF sets: ABM11 [57], MSTW2008CPdeut [58], CT10, HERAPDF15 [59], NNPDF2.3 [32], JR09 [60] (for NNLO calculations) and epWZ [61] (for NNLO calculations). In both figures, the markers represent the cross-sections calculated for a pair of processes using a specific central PDF with its error bars depicting the uncertainty due to the choice of renormalization (μ R ) and factorization (μ F ) scales.…”