Studies Of The Quasi-two-body B Meson Decays In The PQCD Approach

In recent years,LHCb group have collected large number of relevant experimental events for three-body B meson decays.And Belle ? has also began its collection of the data,which will produce large amounts events of the B meson decays.Those make it urgent for us to study the three-body B meson decays.Three-body hadronic B meson decays provide an important place for us to verify the standard model and precisely measurement of the parameters in the standard model.We can use them to deeply study internal structure of hadrons,and these decay processes has opened another door for us to search physics beyond the standard model.The processes of the three-body B meson decays are more complicated comparing with two-body decays.Theoretically,we can neglect the final state interactions,introduce the resonance state,and treat the process of three-body decay as a quasi-two-body case,then employ the perturbative QCD(pQCD)approach based on kT factorization to analyse the quasi-two-body B meson decays.In chapter 2,we briefly introduce the CKM matrix elements,low-energy effective Hamiltonian and hadronic matrix elements in the standard model.In the first work of this thesis,the virtual contributions from D*(2007)0 and D*(2010)± in the decays of B?D*h?D?h are mainly studied.This is also the first time we use the pQCD to study the virtual contribution.With the phenomenological analysis,the following conclusions are obtained:(1)In the range of mD0?+>2.1GeV,the branch ratios of virtual contribution are about 3.9%and 3.7%,respectively,of the two-body results which given in the review of particle physics for the B?D*0?-?D+?-?-and B?D*0K-?D+?-K-decay processes,and the virtual contribution from D*+ is about 5%of the predicted quasi-two-body results with the pQCD;(2)The branch ratios of B0?D*+?-?D0?+?-and B0?D*+K-?D0?+K-are mainly concentrated around the pole mass of the resonance,up to over 90%,due to the narrow decay width of D*+.(3)Based on the dependence of the branching ratio on the decay width,we draw the diagram for the branching ratio of the two-body decay B-?D*0?-and B-?D*07?-vary with the decay width which are extracted from the quasi-two-body decays considering the B(D*0?D0?0)=64.7%,and compared with the corresponding two-body decay branching ratio in the experiment,the decay width for D*0 is approximately to be 53keV.In the second work,we study the contributions of K0*(1430)and K0*(1950)in the three-body decay processes of B?K7ch.The non-perturbative time-like form factor FK?(s)used in this work is calculated from the matrix element from the vacuum state to the K? system.Through the study of the scalar mesons,the decay processes with the scalar mesons as the intermediate state are comprehensively understood,and the time-like form factor for the S-wave is improved,which also helps us in understanding the processes of the QCD in the low energy region.With the calculation and analysis,we found that:The CP averaged branching ratio of the quasi-two-body decay B?K0*(1950)h?K?h is one order smaller than the corresponding branching ratio of B?K0*(1430)h?K?.We compare our predictions with the results in the literature and find that the results predicted by the pQCD approach are in good agreement with the existing date.With the continuous collection of the B meson-related events in the LHCb experiment and super-KEKB,the experimental results will not only provide a strong guarantee for our theoretical results,but also urge us to continuously improve the theoretical framework.