Electroweak physics at the LHCb experiment

This thesis presents a measurement of the cross-section for $W\to e\nu$ production in $pp$ collisions using data corresponding to an integrated luminosity of $2\,$fb$^{-1}$ collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=8\,$TeV. Differential cross-sections as a function of the electron pseudorapidity are measured. The $W^{+}/W^{-}$ cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of $W$ boson branching fractions is determined to be \begin{equation*} \mathcal{B}(W \to e\nu)/\mathcal{B}(W \to \mu\nu)=1.020\pm 0.002\pm 0.019, \end{equation*} \noindent where the first uncertainty is statistical and the second is systematic. Also described is a study of matching and merging schemes and weak showering, as applied to the production of electroweak bosons in association with jets at the LHC. These advanced theoretical tools are seen to provide a good description of event shapes in the central region when compared to measurements performed by the ATLAS and CMS collaborations at a centre-of-mass energy of $\sqrt{s}=7\,$TeV. Matching and merging schemes also provide a superior description of forward $Z+$jets production. The study constitutes a test of matching and merging schemes in a novel region of phase space and can be considered as a validation of the universality of these techniques. Finally, it was determined that current measurements of electroweak physics at LHCb do not yet fully probe the effect of weak showers.