Measurement of the muon charge asymmetry in inclusive $pp\to W+X$ production at $\sqrt{s}=7$ TeV at CMS and an improved determination of light parton distribution functions

Measurements of the muon charge asymmetry in inclusive $pp\to WX$ production at $\sqrt{s}=7$ TeV are presented. The data sample corresponds to an integrated luminosity of 4.7 $\mathrm{f}{\mathrm{b}}^{-1}$ recorded with the CMS detector at the LHC. With a sample of more than twenty million $W\to \mu \nu$ events, the statistical precision is greatly improved in comparison to previous measurements. These new results provide additional constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable $x$ from ${10}^{-3}$ to ${10}^{-1}$. These measurements are used together with the cross sections for inclusive deep inelastic ep scattering at HERA in a next-to-leading-order QCD analysis.