Measurement of Z boson production in association with jets at the LHC and study of a DAQ system for the Triple-GEM detector in view of the CMS upgrade

This PhD thesis presents the measurement of the differential cross section for the production of a Z boson in association with jets in proton-proton collisions taking place at the Large Hadron Collider (LHC) at CERN, at a centre-of-mass energy of 8 TeV. A development of a data acquisition (DAQ) system for the Triple-Gas Electron Multiplier (GEM) detector in view of the Compact Muon Solenoid (CMS) detector upgrade is also presented. The events used for the data analysis were collected by the CMS detector during the year 2012 and constitute a sample of 19.6/fb of integrated luminosity. The cross section measurements are performed as a function of the jet multiplicity, the jet transverse momentum and pseudorapidity, and the scalar sum of the jet transverse momenta. The results were obtained by correcting the observed distributions for detector effects. The measured differential cross sections are compared to some state of the art Monte Carlo predictions MadGraph 5, Sherpa 2 and MadGraph5_aMC@NLO. These measurements provide an important contribution to the understanding of the perturbative quantum chromodynamics theory. Additionally the highest energies ever obtained in laboratories and the exceptional proper functioning of the LHC make possible to explore regions of the phase space never reached so far. Following the LHC machine development plan, the accelerator is expected to provide a higher and higher instantaneous luminosity for the near future and new detector technologies must be studied to handle the large particle rates that are expected. A chapter presenting the development of a DAQ system of the CMS muon detection and triggering system upgrade with Triple-GEM detectors is also included in this thesis. A full experimental set-up has been built at the Interuniversity Institute for High Energies (IIHE) (ULB-VUB) for testing of Triple-GEM prototypes and to show the feasibility of the project. First results were obtained with cosmic muons at the IIHE as well as muons and pions in test beams at CERN and confirm the validity and feasibility of the Triple-GEM project for the CMS upgrade.