Observation and branching fraction measurement of B+ →ψ(2S)φK+ AT√s=8TeV in CMS & Hadron Shower development studies using Geant4 simulations

Heavy quark decays provide a very advantageous investigation to test the Standard Model (SM). Recently, promising experiments with b quark, as well as the analysis of the huge data sets produced at the Large Hadron Collider(LHC) experiment, have led to an increasing study and sensitive measurements of relative b quark decays. In this thesis, a preliminary study is presented for the first time observation of the B+ → ψ(2S)φK+ with a statistical significance above 5 standard deviations using proton-proton collisions at √s = 8 TeV collected with CMS detector at LHC. The data sample, selected on the basis of the dimuon decay mode of the ψ(2S), corresponds to an integrated luminosity of 19.6 fb⁻¹. A total of 140±15 B+ → ψ(2S)φK+ events have been observed. The branching fraction of B+ → ψ(2S)φK+ is measured relative to B+ → ψ(2S)K+, whose absolute branching fraction (BF) is known. The ratio is converted to an absolute branching fraction of B+ → ψ(2S)φK+, including systematics which is determined to be (4.0 ± 0.4(stat) ± 0.6(syst) ± 0.1(BR)) × 10⁻⁶, where the third uncertainty is due to imprecise knowledge of BF. The upper limit of the fraction of B+ → ψ(2S)(non−φ)K+ component in the selected B+ → ψ(2S)K+K−K+ channel is found to be 26% at 95% confidence level.