Measurement of the helicity of the W boson with the CMS experiment

This thesis describes the measurement of the helicity of W bosons as a function of the W-boson rapidity in the $W\rightarrow\mu\nu$ and $W\rightarrow e\nu$ decay channels. The analysis is based on a dataset of 35.9\,$\mathrm{fb^{-1}}$ at $\sqrt{s}$ = 13\,TeV collected in 2016 by the CMS experiment at the LHC. The thesis also presents the measurement of the W-boson double-differential cross section as a function of the transverse momentum and pseudorapidity of the decay charged lepton unfolded to stable-particle level. Both measurements are carried out for each W-boson charge through a simultaneous fit and are complemented by the measurement of the charge asymmetry of W bosons produced at the LHC. All these measurements are performed using an innovative method that allows to unfold the cross section and charge asymmetry directly as a function of stable-particle-level quantities. The measurement of the W-boson helicity and rapidity distribution provides stringent tests of the parton distribution functions, and has been developed with the aim of reducing the theoretical systematic uncertainties that currently limit the precision of the W-boson mass measurement at the LHC. Therefore, some prospects regarding this topic are discussed as well.