R&D; studies on the hadronic calorimeter and physics simulations on the Standard Model and minimal supersymmetric Standard Model Higgs bosons in the CMS experiment

This thesis consists of two main parts: R&D; studies done on the Compact Muon Solenoid (CMS) Hadronic Calorimeter (HCAL) and physics simulations on the Higgs boson for a Minimal Supersymmetric Standard Model (MSSM) and a Standard Model (SM) channel. In the first part, the air core light guides used in the read-out system of the Hadronic Forward (HF) calorimeter and the reflective materials used in them are studied. Then, tests and simulations were performed to find the most efficient way to collect Cerenkov light from the quartz plates, which are proposed as a substitute for the scintillator tiles in the Hadronic Endcap (HE) calorimeter due to radiation damage problems. In the second part physics simulations and their results are presented. The MSSM channel H/A[arrow right]ττ [arrow right]l l v v v v is studied to investigate the jet and missing transverse energy (MET) reconstruction of the CMS detector. The effects of the jet and MET corrections on the Higgs boson mass reconstruction are investigated. In the last part the SM channel gg [arrow right] HH [arrow right] (W + W - )(W + W - ) [arrow right] (j j μ v ) (j j μ v ) is simulated using fast simulation software of the CMS. The results at every step of the simulation are compared to the theoretical results from previous studies.