Search for the Supersymmetric Higgs boson in the $pp \to b + \Phi, \Phi \to b\overline{b}$ channel with the CMS detector at LHC

In this thesis the analysis performed for the search of the Higgs boson predicted by the Minimal Super-symmetric Standard Model (MSSM) is presented. The process on which the search is grounded is the Higgs boson production in association with b-quarks with the subsequent decay in a b-quark pair. The analyzed data sample has been recorded by the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) in Geneva, Switzerland, during the 2011 data-taking. The data sample consists of a total integrated luminosity of L = 4.8 fb-1, recorded with different trigger paths along the 2011 LHC operations. The trigger have been updated during the data-taking in order to cope with the increasing pp collisions instantaneous luminosity provided by the LHC. The background to the signal events has been estimated through two data-driven methods. The systematic uncertainties related to the background have been estimated for both the shape and normalization. The signal is modeled through Monte Carlo simulation technique for different hypothesis of the Higgs boson mass. The systematic uncertainties related to the signal model, from different sources, have been estimated. A possible signal contribution in the analyzed data sample is investigated through a t to the data using the background templates estimated from the data-driven methods and the signal model from Monte Carlo simulation. The systematic uncertainties, as well as the statistics uncertainties, for both the signal and background have been taken into account in the t. The results are compatible with the expected background within the statistics and systematic uncertainties. No signal is found in the data within the sensitivity of the analysis. The sensitivity of the analysis has been calculated in the background only hypothesis. This is reported as upper limits on the cross section of the Higgs boson produced in association with two b-quarks times the branching ratio of the decay into a b-quark pair. This values are also interpreted as upper limits on parameters of the MSSM model. The results of the analysis discussed in this thesis have been combined with those obtained by the DESY (Hamburg, Germany) CMS group, exploiting a different analysis strategy for searching the Higgs boson in the same channel. The combined upper limits from the two analysis improve the sensitivity of the CMS experiment to a Higgs boson signal produced through the tested channel with respect to the single analysis.