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 ± ν μ ) X cross-sections are measured at a proton-proton centre-of-mass energy $\sqrt{s}=5.02$ 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 < p T < 52 GeV. Integrated over p T , the measured cross-sections are ${\displaystyle \begin{array}{c}{\sigma}_{W^{+}\to {\mu}^{+}{\nu}_{\mu }}=300.9\pm 2.4\pm 3.8\pm 6.0\ \textrm{pb},\\ {}{\sigma}_{W^{-}\to {\mu}^{-}{\overline{\nu}}_{\mu }}=236.9\pm 2.1\pm 2.7\pm 4.7\ \textrm{pb},\end{array}}$ σ W + → μ + ν μ = 300.9 ± 2.4 ± 3.8 ± 6.0 pb , σ W − → 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 ${m}_W=80369\pm 130\pm 33\ \textrm{MeV},$ m W = 80369 ± 130 ± 33 MeV , where the first uncertainty is experimental and the second is theoretical.