Approved for the University Committee on Graduate Studies. The analysis of the inclusive photon spectrum from B → X s γ decays is rather challenging due to high backgrounds from photons emitted in the decay of mesons in B decays as well as e + e − annihilation to low mass quark and lepton pairs. Based on 88.5 million BB events collected by the BABAR detector, the photon spectrum above These parameters are useful input to non-perturbative QCD corrections to the semileptonic B decay rate and the determination of the CKM parameter |V ub |.Based on these parameters and heavy quark expansion, the full branching fraction is obtained as: her feels this sense of extended family feeling; Vera really tries to help you achieve the best for you. She is so caring, patient and understanding, and at the same time constructively critical; without her this thesis would not possible.I would like to thank each member of my research group, with whom I have worked closely in the last four years for the analysis presented here, Francesca Bucci, AlanEisner, Colin Jessop, James Libby, Ruth Schmitz, Jane Tinslay and John Walsh. I learned so many things working together with them. I learned how to be meticulous without loosing sight of the big picture, how to be patient, but also ready to move vii on. It has been a wonderful experience to work with them. I must mention that Francesca and Ruth are also very close friends with whom we have shared much more than work. The Standard Model of particle physics is a quantum field theory in four-dimensional Minkowski space that provides an elegant framework to understand and make precise predictions about three of the four fundamental interactions of nature. Tested extensively in the last three decades, it has been shown to be the most successful theory of matter up to the energy scales that experiments have been able to probe. Despite its triumphs however, it is considered to be the effective form of a more fundamental theory, due to both aesthetic reasons, such as the fact that it depends on 18 a priori arbitrary parameters [1], and practical deficiencies, such as the absence of neutrino oscillations.
My years atThe fundamental constituents of matter in the Standard Model are spin-1 2 fermions, which interact through the exchange of spin-1 gauge bosons. The fermions are categorized into two broad groups, depending on whether they carry color charges or not:quarks (u i = u, c, t and d i = d, s, b) and leptons (ν i = ν e , ν µ , ν τ and i = e − , µ − , τ − ).Hence quarks interact with the carriers of the color (strong) force, gluons. While only quarks and charged leptons have electric charge, and thus couple to electromagnetic-
Electroweak InteractionsIn the Standard Model, electromagnetic and weak interactions are governed by a unified chiral gauge theory of gauge group SU (2) L × U (1) Y . While right-handed fermion fields are SU(2) singlets, left-handed fermions of i th generation are represented by SU(2) doublets,unitary matrix known as the Cabibbo-Kobayashi-Maskawa matrix [4].There are thr...