Measurement of the W → μν cross-sections as a function of the muon transverse momentum in pp collisions at 5.02 TeV

The pp → W±(→ µ ±νµ)X cross-sections are measured at a proton-proton centreof-mass energy √ s = 5.02 TeV using a dataset corresponding to an integrated luminosity of 100 pb−1 recorded by the LHCb experiment. Considering muons in the pseudorapidity range 2.2 < η < 4.4, the cross-sections are measured differentially in twelve intervals of muon transverse momentum between 28 < pT < 52 GeV. Integrated over pT, the measured cross-sections are σW+→µ+νµ = 300.9 ± 2.4 ± 3.8 ± 6.0 pb, σW−→µ−ν¯µ = 236.9 ± 2.1 ± 2.7 ± 4.7 pb, where the first uncertainties are statistical, the second are systematic, and the third are associated with the luminosity calibration. These integrated results are consistent with theoretical predictions. This analysis introduces a new method to determine the W-boson mass using the measured differential cross-sections corrected for detector effects. The measurement is performed on this statistically limited dataset as a proof of principle and yields mW = 80369 ± 130 ± 33 MeV, where the first uncertainty is experimental and the second is theoretical.