| For a long time,B-meson physics has been considered as an excellent place to test the Standard Model(SM)and explore New Physics beyond the SM(NP).With the successful operation of the previous generation B factories BaBar and Belle,research on B physics is very active,especially the non-leptonic decays of B mesons.This is because the non-leptonic decays of B mesons can be used to extract the SM parameters such as the CKM matrix elements.On the other hand,study of it can deepen our understanding of the strong interaction dynamics.Measurement of the non-leptonic decays of B mesons is also an important goal of the current Belle Ⅱ and LHCb experiments.Unlike the previous generation of B factories,the LHCb experiment can produce a large number Bs mesons in addition to B0 and B± mesons,which opens up a new field for the study of B physics.In this thesis,we study the two-body and three-body non-leptonic decays of Bs mesons within PQCD(perturbative QCD,PQCD)factorization approach,which is based on recent experimental measurements of the Bs mesons at the LHCb.CP violation has been of intense interests since the discovery of CP violation in neutral kaon system in 1964.In recent years,B factories and LHCb experiments have successively discovered obvious local CP violation in the three-body non-leptonic decays of B mesons(B(u,d),Bs,Bc),which requires a reasonable theoretical explanation.Compared with the twobody non-leptonic decays,the three-body non-leptonic decays of the B mesons involves more complex dynamics.In the three-body decay phase space,the distribution of CP violation is generally non-uniform,but what physical mechanism leads to the observed large CP violation in certain regions of the phase space remains unknown.However,no matter which mechanism,responses a large strong phase difference is generally required.The ρ-ω mixing can just provide the large strong phase difference required for the CP violation,and may also explain that the signal the observed CP violation changes on both sides of p resonance in the LHCb experiment.Therefore,in this thesis,we investigate the influence of the ρ-ω mixing and the interference effect between resonance states of different spins on the CP violation distribution in the threebody non-leptonic decays of B mesons.In the PQCD approach,we calculated the direct CP violation in the decay of Bs0→ρ(ω)φ→π+π-φ and Bs0→ρ(ω)K*0→π+π-K*0 via ρ-ωmixing mechanism.Numerical results show that the CP violation can be enhanced by the ρ-ωmixing mechanism when the invariant masses of the π+π-pair is in the vicinity of the ω resonance.For the decay processes of Bs0→ρ(ω)φ→π+π-φ and B0s→ρ(ω)K*0→π+π-K*0,the CP violation can reach 6%and-50.2%,respectively.Furthermore,taking ρ-ω mixing into account,we calculate the branching ratios of Bs0→ρ(ω)K*0 and Bs0→ρ0(ω)K*0 decays.We also discussed the possibility to observe the predicted CP violation at the LHC.The two-body non-leptonic decays of B mesons is a good place to study the dynamics of strong interaction at low energy.Within the perturbative QCD factorization approach,we study the decay process Bs0→DsP(V).Theoretical calculations for such processes require the Bs→Ds transition form factor(or the wave functions of Bs and Ds mesons)as theoretical inputs.For this non-perturbative quantity,there is still alack of detailed experimental and theoretical studies.Recently,the LHCb collaboration has given the Bs→Ds transition form factor in the Boyd-Grinstein-Lebed(BGL)parametrization from the measurement the Bs0→Ds-μ+νμdecay,which provides the possibility to study the two-body decays Bs0→DsP(V).Therefore,in this thesis,we first use the experimental data of the Bs0→ Ds-μ+νμ semi-leptonic decay process to fit the parameters of Bs and Ds mesons wave function in the perturbative QCD approach.Based on the results,we study the two-body decay and calculate branch ratios of Bs0→DsP(V)in the framework of the perturbative QCD.The numerical results of the branching ratios are BR(Bs0→Ds+π-)=(19.3-7.3-6.0-0.9 +10.3+6.0+0.9)×10-4,BR(Bs0→Ds+ρ-)=(45.5-18.9-14.3-2.4 +25.7+14.8+2.3)×10-4 and BR(Bs0→Ds+K-)=(1.67-0.68-0.54-0.09 +0.75+0.51+0.09)×10-4.Numerical results show that our theoretical predictions of the branching ratios are in agreement with the current experimental measurements within 1σ error.For the Bs0→Ds+K*-process,which has not been measured get,we hope that the LHCb experiment can provide a test for our theoretical result in the future.Due to the large number of Bs mesons events provided by the LHCb experiment,theoretical study of Bs meson has entered a new era.Although the current theoretical studies on the threebody decay of the Bs meson is still in the early stage,there are still many theoretical problems to be solved.In the future,more and more experimental data at the LHCb and Belle Ⅱ will help us continuously improve and develop relevant theories.At the same time,we hope that our theoretical studies of the B-meson two-body and three-body non-leptonic decays will provide some help for experimental searches and the analysis of the experimental data. |
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