Study Of Quasi-two-body Decays B→D［ρ(x)→］ππ In The PQCD Factorization Approach

The B meson physics provides an ideal place to test the standard model(SM)pre-cisely and to search for the signal of the new physics beyond the SM.In recent years,more and more three-body hadronic B meson(B(u,d),BS,Bc)decays have been observed by experiments carried on in B factories and LHCb,therefore,the relevant theoretical predictions are urgently needed.Compared to the two-body hadronic B meson decays,the kinematics and final state interactions of the three-body decays are much more com-plicated,which makes the study of the three-body hadronic B meson decays a hot topic in the heavy flavor physics.In this thesis,the author studies systematically some three-body hadronic B meson decays involving a D/Ds meson as one of the final states by employing the framework of the perturbative QCD(PQCD)factorization approach.On the review part(Chapter 1-3),the author firstly makes an introduction for the basics of the standard model of particle physics and relevant theories about B meson physics,including the CP violation in B meson decay and the popular methods to calculate the hadronic matrix element based on the QCD dynamics:the QCD factorization(QCDF)approach,PQCD factorization approach and Soft Collinear Effective Theory(SCET),especially the PQCD factorization approach which has been employed in this thesis.In the Chapter 3,the author provides a short overview for the kinematics of the three-body decays and the current status for both the theoretical and experimental studies,as well as the framework for the three-body hadronic B meson decays in the PQCD factorization approach.In the Chapter 4 and Chapter 5,the author makes a systematic study for the quasi-two-body B meson decays B(s)/Bc→ D[ρ(770),ρ(1450),ρ(1700)→]ππ in PQCD factor-ization approach.Besides quasi-two-body decays B(s)/Bc → D[ρ(770)→]ππ,we also calculate the branching ratios of two-body decays B(s)/Bc→ Dρ(770)with the same parameters in the framework of PQCD factorization approach.Through analytical cal-culation and numerical analysis,we have the following observations:(1)The PQCD predictions for the branching ratios of the considered quasi-two-body decays B(s)→ D[ρ(770),ρ(1450),ρ(1700)→]ππ are in the range of 10-10-10-2 For those decays which have been measured by experiments,our results agree with the experimental data.(2)The results show thatB(B(s)→ D[ρ(770)→]ππ≈ B B(s)→ Dρ(770)),it is a new indication for the reliability of the PQCD factorization approach.Besides,one can extract the decay rates for the two-body decays B(s)→Dρ(1450),ρ(1700))from the PQCD predictions for the branching ratios of the corresponding quasi-two-body decay modes.(3)The PQCD predictions for the branching ratios of the quasi-two-body decays Bc→D[ρ(770),ρ(1450),ρ(1700)→]ππ are in the order of 10-9 to 10-5 and the direct CP violations around(10-40)%in magnitude.All those PQCD predictions will be tested in the future experiments.(4)The contributions from the nonfactorizable and annihilation-type diagrams are also found to be of great importance in charmed B meson decays and should be consid-ered.It is still in the early stage for both the theoretical studies and the experimental measurements of the three-body hadronic B meson decays.The future experiments,such as the LHCb and Belle-II,will provide more and more data and it will help us to develop the theoretical models step by step,improve the accuracy of theoretical predictions.Our studies can also provide effective support for the plan of the experiments and the data analysis.