Study of Triple-GEM detector for the upgrade of the CMS muon spectrometer at LHC

This doctoral thesis is part of the upgrade of the CMS experiment at the Large Hadron Collider of CERN, the LHC. CMS, together with the ATLAS experiment, led to the discovery of the Brout-Englert-Higgs boson in 2012. But the LHC research program is not over yet. Indeed, the LHC is intended to operate even at least 20 more years. During this period, the luminosity will grow gradually up to five times its nominal value of 1034 cm−2 s −1 initially foreseen. This increase in luminosity requires the LHC experiments, like CMS, to upgrade their detectors as well as their data acquisition system. One of the next major CMS upgrade is the addition of a new detector layer in the forward muon spectrometer of CMS. The technology that has been chosen by the CMS collaboration for this upgrade is the Triple Gas Electron Multiplier (Triple-GEM) technology. This upgrade aims to maintain the trigger performance despite the increasing rate of particles (> 1 kHz/cm2 ) and will also improve the reconstruction of muons tracks, thanks to a excellent spatial resolution (∼ 250 µm). It is the study and characterization of this technology that is the subject of this thesis. This characterization of the Triple-GEM detectors starts with a detailed study of the time resolution. This study has been performed using different Monte Carlo simulations like GARFIELD, and has demonstrated that the Triple-GEM detectors equipped with the new VFAT3 electronics (developed for this upgrade) fulfill the requirements for the CMS upgrade. Then we have studied different detector prototypes. First, we have built two small 10×10 cm2 prototypes and developed a test bench at the ULB laboratory. This test bench has allowed us to study another important parameter of the Triple-GEM detectors: the gain. Later, we also had the opportunity to take part in the data taking and analysis of a test beam campaign at CERN. The analysis of the data of this test beam is also presented in detail. The last part of this work concerns the study of the spatial resolution. We have estimated the spatial resolution of the Triple-GEM detector equipped with a binary electronics by Monte Carlo simulations as well as analytically. This study has been extended to other detector technologies like the Micromegas and the silicon sensors.