Study Of Two-body Nonleptonic Charmless B Decays And The Supersymmetric Quantum Effects

In the past 30 years, the standard model theory has been extensively tested. However, some puzzles still exist and can not be explained faultlessly. So people generally believe that the standard model theory is only an effective theory at Fermi scale and at a higher scale new physics beyond the standard model must be there. In order to find new particles, the running of the forthcoming large hadronic collider (LHC) which has superhigh energy is needed. In the current B meson experiments and the intending LHC-B experiments, people may firstly find the signal or evidence of the existence of new physics through the research on the production and decays of B meson. In this thesis, we made a systematic study of the two-body nonleptonic charmless B decays in the framework of the standard model and the minimal supergravity model.In the first three chapters, we firstly discussed the main embarrassments the standard model faced, introduced the motivation for expecting new physics, and gave the reasons why supersymmetry is of considerable interest. A brief summary of the theoretical frameworks of the standard model and kinds of supersymmetry models and some relevant discussion were given in the second chapter. In chapter three, we firstly made a review of the theoretical framework of B physics, gave a brief description of several methods for calculating the hadronic matrix elements, and discussed the QCD factorization approach in details.Chapter four is the part of our own work. We firstly calculated the charged-higgs,charginos, neutralinos and gluinos penguin diagrams appearing in the mSUGRA model, extracted out F_1,2^L,R and gave the analytical expressions of the new physics contributions to the Wilson coefficients C_k(Mw). Through scanning in the supersymmetric parameters spaces, we found that the supersymmetric (SUSY) corrections to the Wilson coefficients C_k (k = 3～10) are very small and can be neglected safely, but the leading order SUSY contributions to C_7r(Mw) and C_8g(M_w) can be rather large and even change the sign of the corresponding values in the standard model.Also in chapter four, by employing the QCD factorization approach, we studied the new physics effects to the branching ratios and CP-violating asymmetries of these 80 two-body charmless hadronic B→M₁M₂(M_i=P,V) decays, and made a detailed discussion about those channels which had data given by B meson experiments and were interesting in the phenomenological research. For the branching ratios of those channels, since the large uncertainties coming from both theories and experiments are there, the theoretical predictions in both the SM and the mSUGRA model can be consistent with the corresponding data by choosing appropriate parameters. However, for some channels the SUSY contributions in our considered model can improve the consistency of the theoretical predictions with the data. At the considered typical parameter points, we found: (a) the SUSY contributions are always very small for both case A and C; (b) for those tree-dominated decays, the SUSY contributions in case B are also very small; (c) for those QCD penguin-dominated decay modes, the SUSY contributions in case B can be significant, and can provide an enhancement about 30%～260% to the branching ratios of B→K(Ï€,η^',Φ),K^*(Ï€,ω,Φ,ρ) decays, but a reduction about 30%～60% to B→K(ρ,ω) decays.In chapter four, we also calculated the CP-violating asymmetries of these 80 two-body charmless hadronic B→M₁M₂(M_i= P, V) decays in the standard model and the mSUGRA model and gave the new physics corrections to all of them. Since there are too many input parameters and have large theoretical uncertainties, our predictions can only give a proper order of magnitudes. Compared with the SM predictions, in Case A and C, the SUSY contributions are also generally small. But in Case B, things are different: (a) for B→PP decays, the SUSY corrections on the CP violations are generally small or moderate and trend to make the SM predictions decreased. The largest correction is about -30% for B⁰→K^±π^? decays; (b) for B→PV decays, the SUSY corrections on the direct or indirect CP violations of most channels can be rather large. The largest corrections even reach a factor of 7 for the decay B⁰→ηρ⁰. Others can also reach from—30% to 250%; (c) for some B→VV decays, the SUSY corrections can also be large and the corrections can reach -40%～30%.Lastly, in chapter four, considering the so-called cancellation mechanism and the constraint from the new data of the electron and neutron electric dipole moment (EDM), we calculated the tolerable range of the two phaseΦ_μ,Φ_A in the general mSUGRA model and found the phaseΦ_μis strongly constrained by the data of EDM:Φ_μ< 0.1 (<10^-3) for the case of small (large) tanβ, but no limit on the phaseΦ-a can be derived from the EDM data. By considering the so small tolerable range of the two phase, we recalculated the CP-violating parameters of B→πK and found the SUSY corrections were generally small and made no interesting results.In the last chapter, a short summary of this thesis and some remarks on future development of B physics in the forthcoming years were given.