Phenomenological Studies Of New Physics In B Mesons And Baryons Weak Decays

The Standard Model(SM)in the particle physics has been established to be the best theory to describe the strong,magnetic and weak interactions,and its predictions stand almost all the tests of the experiments until now,especially for the discovery of the Higgs boson.However,the SM is not perfect,although it can explain the mechanism of the electro-weak symmetry breaking——Higgs mechanism,it's not clear that if the scalar doublet responsible for the electro-weak symmetry breaking is one or not.Moreover,there are some observables depart from the predictions of the SM,such as R(D(*))RK and so on.These questions leave some space for the New Physics(NP).For the study on new physics,on the one hand,we can test the sign of NPs from high energy experiments,on the other hand,we can explore NPs indirectly through the high luminosity and precise low energy flavor processes.Although new particles can not be produced at low energy,they can give corrections to the flavor processes,and then we can test the signs of NPs with very high energy.In this thesis,we mainly study the effects of two NP models in the decays of B mesons and ?b baryons and neutral B mesons mixing.One of the NPs we consider is the Two-Higgs-Doublet-Model(2HDM),specificly,the color-octet 2HDM within the hypothesis of minimal flavor violation(MFV);and the other is the leptoquark(LQ)model containing scalar and vector scenarios.Firstly,we introduce the meaning and development of the study on the B physics in chapter 1 and chapter 2,respectively.In chapter 3,we calculate the observable ?Ms,d in Bs,d-Bs,d mixing within the color-octet 2HDM,which in this thesis is called as MW model.Unlike the usual case,we keep the momentum and the mass of the external b quark in our calculation.We also calculate the observable B(Bs,d??+?-)within the MW model.Combining the study of Z? bb and the radiative decay B? Xs(K*,?)?,we constrain the parameters of the MW model.We find that the Yukawa coupling ?u,is stringently constraint,but the other coupling ?d is not,neither is the ?1 in the potential of Higgs.What's more,the exclusive and inclusive radiative decays of B meson behave differently with respect to other processes considered in this thesis,so they can give complementary information.As both the scalar and vector LQ models can explain the anomalies in the observables R(D(*)of the exclusive semi-leptonic decays B?D(*)???,we consider the effects of these two interesting models in the decays of B mesons and baryons.In chapter 4,we exclude two solutions of the scalar LQ scenario via the pure leptonic decay Bc-??-?? firstly,and then we explore the effects of the remaining two solutions in the radiative decay Bc?????,the ex-clusive semi-leptonic decays B?D(*)??? and the inclusive semi-leptonic decay B?Xc???.We find that the remaining two solutions of the scalar LQ scenario can enhance almost all the observables considered in this thesis with respect to the predictions of the SM,except for the lon-gitudinal polarizations of D*meson and ? lepton as well as the lepton-side forward-backward asymmetry.In chapter 5,we explore the effects of the two LQ scenarios in the decay ?b??c???which is also induced by the quark level transition b?c???.We find that both the two LQ sce-narios enhance almost all the observables equally,except for the longitudinal polarizations of?c.baryon and ? lepton as well as the lepton-side forward-backward asymmetry,so the two LQ scenarios can not be distinguished from each other through this process,and the two solutions of each LQ scenario can not be distinguished,either.In theory,with the development of Lattice QCD,the nonperturbative parameters due to the strong interaction at the low energy region can be calculated with higher precision,and then many processes of B meson or baryons decays can be predicted more reliably.In experiment,the integrated luminosity of the running LHC and the future SuperKEKB will be improved greatly,providing more events for production and decay of B mesons as well as better prospect for the study on B physics.