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

A bstract The pp → W ± (→ μ ± ν μ ) X cross-sections are measured at a proton-proton centre-of-mass energy $$ \sqrt{s}=5.02 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>5.02</mml:mn> </mml:math> 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 &lt; η &lt; 4 . 4, the cross-sections are measured differentially in twelve intervals of muon transverse momentum between 28 &lt; p T &lt; 52 GeV. Integrated over p T , the measured cross-sections are $$ {\displaystyle \begin{array}{c}{\sigma}_{W^{+}\to {\mu}^{+}{\nu}_{\mu }}=300.9\pm 2.4\pm 3.8\pm 6.0\ \textrm{pb},\\ {}{\sigma}_{W^{-}\to {\mu}^{-}{\overline{\nu}}_{\mu }}=236.9\pm 2.1\pm 2.7\pm 4.7\ \textrm{pb},\end{array}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtable> <mml:mtr> <mml:mtd> <mml:msub> <mml:mi>σ</mml:mi> <mml:mrow> <mml:msup> <mml:mi>W</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msub> <mml:mi>ν</mml:mi> <mml:mi>μ</mml:mi> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>300.9</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.4</mml:mn> <mml:mo>±</mml:mo> <mml:mn>3.8</mml:mn> <mml:mo>±</mml:mo> <mml:mn>6.0</mml:mn> <mml:mspace/> <mml:mi>pb</mml:mi> <mml:mo>,</mml:mo> </mml:mtd> </mml:mtr> <mml:mtr> <mml:mtd> <mml:msub> <mml:mi>σ</mml:mi> <mml:mrow> <mml:msup> <mml:mi>W</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:msub> <mml:mover> <mml:mi>ν</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>μ</mml:mi> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>236.9</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.1</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.7</mml:mn> <mml:mo>±</mml:mo> <mml:mn>4.7</mml:mn> <mml:mspace/> <mml:mi>pb</mml:mi> <mml:mo>,</mml:mo> </mml:mtd> </mml:mtr> </mml:mtable> </mml:math> 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 $$ {m}_W=80369\pm 130\pm 33\ \textrm{MeV}, $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:mi>W</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>80369</mml:mn> <mml:mo>±</mml:mo> <mml:mn>130</mml:mn> <mml:mo>±</mml:mo> <mml:mn>33</mml:mn> <mml:mspace/> <mml:mi>MeV</mml:mi> <mml:mo>,</mml:mo> </mml:math> where the first uncertainty is experimental and the second is theoretical.