الفهرس 
Theoretical BackgroundOnly 14 pages are availabe for public view
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Abstract
Since the CMS and ATLAS experiments at the European Center for Nuclear Research CERN Large Hadron Collider (LHC) in Geneva, Switzerland, discovered the Higgs boson in 2012, physicists have worked to precisely measure its properties and gain a deeper understanding of the underlying electroweak symmetry breaking process. In 3 August 2020, ATLAS and CMS experiments announced new results showing the decay of the Higgs boson into two muons. This physics process is very rare such that nearly every 5000 events only one Higgs boson decays into muons. Despite its very small branching ratio (due to the small coupling between Higgs and a light fermion like muon), the Higgs decay into dimuons is a very clean channel that allows to measure the coupling of the Higgs to second-generation fermions and could be used as a tool to probe Physics Beyond Standard Model (BSM). Additionally, to verify our understanding of the Higgs potential and look for hints for BSM searches, the search for Higgs boson pair production is essential in this endeavour.
The LHC foresees a Phase 2 upgrade for its accelerators as well as its four main experi- ments (CMS, ATLAS, ALICE, and LHCb) during the long shutdown 3 (LS3) in 2024. This upgrade will allow the LHC to cope with the challenging radiation environment during the high luminosity operational phase (HL-LHC). This imposes strict requirements on detector char- acteristics, particularly their capability to sustain high event rates and substantial radiation doses and hence the choice of gas electron multipliers (GEMs). Thus, the measurement of their performance (mainly for GE2/1 detectors in this thesis) is mandatory.
This thesis consists of four chapters:
• Chapter1: briefly introduces the SM and discusses its shortcomings, which motivates its extension to Beyond the Standard Model (BSM) theories with the Two Higgs Doublet Model (2HDM) being the simplest extension.
• Chapter2: describes the experimental setup for the Large Hadron Collider (LHC), fol- lowed by a detailed explanation of the CMS experiment with its various sub-detectors. A brief overview on the CMS GEM project is also presented.
• Chapter3: this chapter briefly explains the procedure of the Quality Control (QC) deployed to the CMS GEM detectors, more specifically the GE2/1 detectors (foreseen to be installed during the Long Shutdown 3 in 2024 for the HL-LHC upgrade) to test their performance. The assembly steps for the GEM modules is also described. Finally, a detailed description of the gain uniformity test conducted to one of the GE2/1 modules is introduced together with the results.
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• Chapter4: gives a detailed description for the search for a single Higgs boson production in the SM in µ+µ≠ decay channel as well as a pair Higgs production results from the decay of heavy neutral CP-even Higgs boson in b¯b4µ channel within the context of the
Type-I 2HDM at the HL-LHC. It also reviews the Monte Carlo event simulation used in this thesis.