Measurement of exclusive two-photon processes with dilepton final states in pp collisions at the LHC

The unification of the electromagnetic and weak forces is a cornerstone of the standard theory of elementary particles and fundamental interactions. At the Large Hadron Collider the processes of pair production via fusion of two exchanged photons provide a unique laboratory both for testing the standard theory and for search of new phenomena in high-energy physics. In this thesis such a two-photon exclusive pair production in pp collisions has been studied experimentally, at two centre of mass energies using the data collected with the CMS experiment during LHC's Run-1. Thanks to large, effective photon fluxes and the outstanding performance of the CMS apparatus clean two-photon signal samples could be extracted. The novel track-based exclusivity selection was instrumental for making successful measurements in an extremely demanding LHC environment. In particular, the "reference" two-photon production of lepton pairs has been measured and investigated in detail, including extended phenomenological studies. A new formalism has been implemented in Monte Carlo simulations using the so-called $k_T$ factorisation scheme. Finally, the two-photon production of weak boson pairs has been studied through the analysis of the data collected with CMS at 7 and 8 TeV. Beside the first observation ever made experimentally of the $\gamma\gamma\rightarrow WW$ process, the measured production rate has been used to extract the best world limits on anomalous behaviour of the $\gamma\gamma WW$ as well as the $\gamma\gamma ZZ$ quartic gauge boson couplings. In addition, the Precision Proton Spectrometer project has been also portrayed - the PPS detectors will allow to measure forward scattered protons, and hence to tag two-photon processes. In particular, one of the possible, ultrafast timing detectors to be installed in the spectrometer is characterised: the GasToF Cerenkov time of flight detector