Research On The Second-order Head Modification Of B??? Decay Process

Since the discovery of the heavy b quark in 1977, the B meson physics has become a hot topic in the study of heavy flavour physics. A lot of researches have been done during the past years, in both the theoretical studies and the experimental measurements. We usually have three main objectives of B meson physics:(1) to find and measure the CP violation of the B meson system, (2) to test the standard model (SM), and (3) to find the signal or evidence of new physics beyond the SM. The main difficulty is the calculation of hadron matrix elements. The method of effective Hamiltonian has been improved greatly, however, because of the appearances of the non-perturbative QCD contributions in the B meson hadronic decay processes, the evaluations for the B meson transition form factors and hadron matrix elements do have large theoretical uncertainties. During the past decade, although a lot of works have been done in studying the charmless hadronic two-body B?M2M3 decays at the leading order (LO) level or the partial next-to-leading order (NLO) level, but the theoretical calculations still have relatively large errors. In this paper we considered the B?PV decays, focusing on the five B??? decay modes, by employing the pQCD factorization approach, with the inclusion of the full LO contributions and all currently known NLO contributions. Besides these pieces,, we also consider the effects of those newly known NLO Twist-2 and Twist-3 contributions to the relevant form factors.The second chapter is the brief review part of this thesis. Firstly we gave an outline to the basic theory of the standard model (SM). Than a brief introduction for the CKM mixing matrix of quark system, the low energy effective Hamiltonian method, the decays and mixings of the B meson system and the definitions of the various Hadronic matrix elements. The main concern of of this review part is the detailed introduction about the PQCD factorization approach to be used in this thesis.In the third chapter, we firstly give an introduction for the hadronic matrix element and meson wave functions, and then present the explicit expressions for those decay amplitudes for the considered B?PV decay modes, with the inclusion of both the LO and NLO contributions. In chapter four, we calculate and present the pQCD predictions for the branching ratios and the CP-violating asymmetries of the five B ??? decays. Based on the analytical and numerical results, we found the following points:1. For the branching ratios of the five considered B ??? decays, the agreement between the PQCD predictions and the data are improved after the inclusion of the next-to-leading order contributions. The effects of the next-to-leading order contribution are clear and moderate in size.2. For all the five B ??? decays, the next-to-leading order contributions are mainly due to vertex corrections, which amounts to more than thirty percent of the total correction. For B0 ??~0?~0 decay, there is no NLO correction from the quark-loops and the chromo-magnetic penguins, while the NLO correction from Wilson coefficient is about thirty percent. For the other four decay modes, contributions from the quark-loops?the chromo-magnetic penguins and the form factors are relatively small.3. For the B~+??~0?~+ decay, the pQCD prediction for its direct CP violation agree well with the data. For B0 ??~0?~0 decay, however, the pQCD prediction is very small, ?0.6% in size. For other three decay modes there still exist some differences for the CP violation between the theory and and the experimental measurements. But the gap between the theory and the available data become narrow after the inclusion of the NLO corrections.In the final chapter, a short summary of this thesis and some remarks on future devel-opment of B meson physics are given.