Studies On Semileptonic B And B~* Mesons Decays And Possible New Physics

The semileptonic ???*meson decays induced by the tree-level b?plvl?p-u,c?transitions are legal within the Standard Model?SM?.In this thesis,we focus on the studies on the semileptonic ???_u,d,c,s^*??P,V?l-???l?P=D,D_s,?,K;V=D*,D_s^*,J/? and l=e,?,??decays within the SM.Meanwhile,due to the tensions in B weak decays provide possible hints towards New Physics?NP?,we also study the NP effects in the semileptonic B and ???*mesons decays.In Chapter 1,we begin with an introduction for the basis of the SM.In Chapter 2 and 3,we study the semileptonic Bu*,d,c,s??P,V?l-???l decays within the SM and present our predictions for branching fraction?decay rate?,lepton spin asymmetry,lepton forward-backward asymmetry and ratios.We can find that all of the semileptonic ???*decay modes induced by b?clvl transition have relatively large branching fractions of O(10^-9)?O(10^-7),and hence are hopefully to be measured by the future experiments.Furthermore,as bottomonium could also decay through b?clvl transition at quark level,we study the tree-dominated semileptonic????nS??Bclvl?n=1,2,3?decays in Chapter 4.It could be found that all of the tree-dominated and CKM-favored????nS?weak decays have the branching fractions of the order O(10^-10?10^-9)and the measurement of semileptonic????nS??Bclvl decays is impossible at LHCb,CMS and Belle-II.In Chapter 5,motivated by recent results from LHCb,Babar,and Belle Collaborations on semileptonic B decays could provide possible space for NP,we have constrained the parameter spaces of NP couplings from the present experimental data in the model-independent vector and scalar scenarios.Using the fitted parameter spaces,we probe new physics effects in the semileptonic B?Pl-???l?P=D,D_s,?,K?decays induced by b??u,c?l-???l transitions.Meanwhile,the scalar type couplings provide significant contributions to all of the observables.Finally,we have studied the RPV SUSY effects in the leptonic B_c?l-???l and semileptonic B?D?*?l-???l decays in Chapter 6.Finally,we find that R?D*?could be enhanced by the the constrained slepton exchange coupling,but it still could not reach the lower limit of its 95% confidence level experimental data. Our results will offer a reference for searching the B^* weak decays and possible hints for NP in future experiments.