Measurement of inclusive and differential cross sections for single top quark production in association with a W boson in proton-proton collisions at $\sqrt{s}= 13 \text{ TeV}$

The main objective of this thesis is the study of the production of a top quark in association with a W boson (tW proccess) using proton-proton collision data collected by the CMS experiment at the LHC during Run 2 at a centre-of-mass energy of $\sqrt{s} = 13\text{ TeV}$ and corresponding to a total integrated luminosity of $138 \text{ fb}^{-1}$. The inclusive cross section of this process was measured obtaining a value of $79.2\pm 0.9 \text{ (stat.)}^{+7.7}_{-8.0}\text{ (syst.)}\pm 1.2\text{ (lumi.) pb}$. The total 10% uncertainty achieved provides the best precision so far for this process. This experimental cross section is compatible with the standard model (SM) predictions at aNNLO+NNLL in QCD, and with the recent estimations at aN${}^3$LO+NNLL, also in QCD. The normalised differential cross section at particle-level for this process was estimated as a function of several physical observables of the final-state objects. The results are confronted with different simulations at NLO in QCD interfaced with two different parton shower generators. There is an overall agreement with the SM expectations. There are, however, some discrepancies that have been also observed in other top quark production modes. The small differences between the predictions point to small effects due to the interference with $\text{t}\bar{\text{t}}$ in the fiducial region chosen. The future Phase-2 upgrade of the CMS detector is driven by the important challenges imposed by the harsher condition expected at the High Luminosity LHC (HL-LHC). A description of the efforts carried out to characterize the ageing of the muon detectors and to study a new trigger algorithm that takes advantage of the new electronics that will be installed is included.