Study Of The Time-Dependent CP Violation In B_s~0??~+?~-Decay Within The Aligned Two-Higgs-Doublet Model

The Standard Model(SM),which is constructed on the basis of Quantum Field Theory,is the basic theory used to describe the elementary particles as well as the interactions among them.The SM unifies the electromagnetic,weak and strong interactions.With the development and progress of experiments,more and more data have constantly verified the validity of the SM.Although the SM has achieved great success,there are still some phenomena observed in experiments that the SM can not explain adequately,such as the matter-antimatter asymmetry of the universe,dark matter and dark energy,as well as the origin of neutrino mass,and so on.These phenomena imply the existence of New Physics beyond the SM.The Flavor-Changing Neutral Current(FCNC)decay Bs0??+?-is regarded as one of the most important processes that can provide a good test of the SM and a probe into NP.Within the SM,this decay is suppressed by the Glashow-Iliopoulos-Maiani mechanism and suffers from the so-called helicity suppression.As the helicity suppression does not occur for the contribu-tion from scalar interactions,the decay Bs0??+?-is very sensitive to such kind of inter-actions.Many NP candidates involve the scalar interactions,such as the Two-Higgs-Doublet Model(2HDM),which have been investigated in this thesis.The 2HDM is one of the simplest extensions to the SM Higgs sector.However,the FCNC couplings could be too large in the most general 2HDM.In order to solve this problem,the Aligned Two-Higgs-Doublet Model(A2HDM)has been proposed.In this model,Since the two Yukawa coupling matrices describing the interaction between the scalar doublet and the right-handed fermion of the same type differ only by one multiplication factor in the flavor space.Therefore,all tree-level FCNCs are forbidden in the A2HDM.Finally,the Yukawa couplings in the A2HDM are controlled by the three parameters ?u ?d,and ?l.At the same time,since these three parameters can be complex,they could provide new sources of CP violation beyond the SM.In this thesis,we have studied the time-dependent CP violation of Bs??+?-decay in the A2HDM.In the A2HDM,we have systematically calculated the flavor-specific CP asymmetry assl,the CP-violating phase ?s and the mass difference ?Ms in Bs0-Bs0 mixing,as well as the branching ratios of Bs0??+?-and B?Xs? decays.After taking into account the most recent experimental data of these observables,we put combined constraints on the parameter space of the A2HDM.Then,in the allowed parameter space,we made predictions for the time-dependent CP-violating observables C??,S??,and A????in the decay Bs??+?-.Their dependence on the model parameters and the correlations among them have been investigated in detail.In addition,effects of the A2HDM on the time-dependent CP asymmetry ACP(t)have also been discussed.This thesis is organized as follows:In Chapter 2,we give a brief introduction to the SM of particle physics as well as the theoretical basis involved in this thesis.In Chapter 3,we present our calculations of Bs0-Bs0 mixing and Bs0??+?-decay within the A2HDM,which makes a preparation for the combined constraints on the model parameters.In Chapter 4,through employing the allowed parameter space of the A2HDM under the combined constraints from the relevant observables in the two above processes and the decay B ?Xa?,we make our predictions for the time-dependent CP asymmetries of Bs??+?-decay in the A2HDM.Our conclusions and expectations are made in Chapter 5.