Discovery potential of the Standard Model Higgs in CMS at the LHC

This thesis presents the discovery potential of the Standard Model Higgs boson in the CMS experiment at the LHC. Detailed studies have been carried out to evaluate the detector performance in the difficult $\rm H\to\gamma\gamma$ channel. The electromagnetic crystal calorimeter is of main importance in this channel and it has been designed according stringent performance requirements. Test beam data of lead tungstate crystals have been analysed and it is shown that the performance of the crystals can meet the requirements. The Higgs decay into two photons has been studied with full detector simulation and the Higgs mass has been reconstructed. A potential danger for the photon measurement are the photon conversions in the detector material in front of the electromagnetic calorimeter. Different methods to recover these converted photons are developed and it is shown that, including the recovered conversions does not degrade the Higgs mass resolution. To complete the full Standard Model Higgs discovery range, studies of the other decay channels are reviewed and updated taking into account the next to leading order corrections to the cross-sections. A new study for the $\rm H\to ZZ\to2$l2$\nu$ channel shows that it can give an important contribution above $m\sb{\rm H}$ = 400 GeV. An estimate of the integrated luminosity needed for an observable Higgs signal is derived. It is shown that a fast discovery (integrated luminosity less than 10 fb$\sp{-1}$) can be expected if the Higgs mass is in the range of 130-550 GeV. The most difficult regions are the low mass range ($m\sb{\rm H}<120$ GeV) and the very high mass range ($m\sb{\rm H}>600$ GeV). With 100 fb$\sp{-1}$ of integrated luminosity the full mass range can be covered.