B_s�'(ρ, ω)K, (ρ, ω, φ)η～(′) Decays In The PQCD Approach

Since 1980's, the B meson physics has achieved great success in both theoretical and experimental aspects. Along with the prosperous experimental evolvements in two B meson factories, B meson physics has become one of the most important and the most popular research field in the particle physics. B meson decays provide a good place to test the SM, CP violation and to search for the new physics. Confronted with the precise experimental data, it is an urgent task for theorist to evaluate the B meson decays with high precision. In order to improve the precision for the evaluation of the hadronic matrix elements of B meson decays, people have developed many methods dealing with this problem, such as: naive factorization, QCD Factorization approach, perturbative QCD (PQCD) factorization approach, etc. PQCD approach, which based on the K_t factorization, was first put forward by Hsiang-nan Li. With the Sudakov suppression from K_t and threshold resummations, there will be no end-point singularities. This makes the pQCD approach more reliable to study the B meson decays.Starting with the basic low energy effective theory, the author presents a brief review for the operator product expansion, the four-quark operator base, and show and compare the different factorization approaches. A detailed introduction for the basic idea and the key points of the pQCD factorization approach is given also. In this thesis, we calculated the branching ratios and CP-violatinf asymmetries for some two body non-leptonic decays: B_s→(ρ,ω)K and B_s→(ρ,ω,φ)η('). The main theoretical predictions are as follows:(1) For B_s→(ρ,ω)K decays, the branching ratios based on the pQCD approach are generally small ( say,～10^-7 in magnitude) for the pure neutral decay channels. For the decay mode B_s→ρ⁺K^-, however, the pQCD predictions are rather large, Br(B_s→ρ⁺K^-)～10^-5. The CP-violating asymmetry for this decay channel is aslo large,～-12%, and therefore can be tested in the forthcoming LHC-b experiments.(2) For the decay channels B_s→(ρ,ω,φ)η('), we found that: Br(B_s→ρ⁰η)≈0.07×10^-6, Br(B_s→(ρ⁰η')≈0.10×10^-6, Br(B_s→ωη)≈0.02×10^-6, Br(B_s→ ωη')≈0.13×10^-6, Br(B_s→φη)≈2.7×10^-5 and Br(B_s→φη')≈2.0×10^-5。(3) The possible gluonic contributions to all considered B_s decay modes are small in size: less than 3% for B_s→(ρ,ω,φ)ηdecays, and about 10% for B_s→(ρ,ω,φ)η' decays.(4) The PQCD predictions for the CP-violating asymmetries of the considered decays are generally not large in magnitude.At the end of the thesis, a short summary and some remarks on future developments of B meson physics in forthcoming years are given.