Studies Of The Two-body Charmless Hadronic B_s Meson Decays In The PQCD Factorization Approach With The Inclusion Of The NLO Contributions

During the past decades,the Standard Model(SM)of the particle physics has achieved rapid development and great success.In the July of 2012,particularly,the ATLAS and CMS collaborations announced the discovery of the Higgs boson,the last missing part of the SM is found finally.Since the B meson(including Bu,d,s,c)is rather heavy,a large number of decay channels are open,calculated theoretically and have been measured experimentally.On the theory side,the comprehensive studies of the B meson decays can offer us rich opportunities to test the SM precisely and to search for the origin of CP violation and even the possible signals or any evidence of the new physics beyond SM.On the experimental side,the early two B factory experiments(BaBar and Belle)have already accumulated a large amount of B meson events,especially Bu,d mesons.They found the large CP violation of the B meson system and measured the branching ratios,CP violations and other physical observables of the several hundred B meson decay modes.Generally speaking,most of the experimental measurements do agree well with the SM predictions within the errors and there is no any solid flavor-related evidence for the existence of the new physics beyond the SM.Furthermore,with the ongoing running of the LHCb,besides Bu,d mesons,more and more Bs/Bc events will be collected,and the future experiments(say LHCb plus Belle-?)could provide us a huge data sample:about two orders higher than we have at present.We therefore believe that a new "Golden Era" of B meson physics is coming again.Theoretically,the most important part of the B physics is the calculation of the transition matrix elements.So far,there exists no completely self-consistent methods because of the complicated underlying dynamics in these decays.Based on the QCD dynamics,three main approaches have been proposed to deal with the B meson decays,namely the QCD factorization(QCDF)approach,the perturbative QCD(PQCD)factor-ization approach and the Soft-Collinear Effective Theory(SCET).Under the framework of the PQCD factorization approach,the author makes a comprehensive study for all the two body Bs0?PP,PV,VV decays(here P=(?,?,?,?')and V=(?,?,?*,?)are light charmless mesons).The author focus on investigating the effects of the NLO contribution-s,such as the QCD vertex corrections(VC),the quark loops(QL),the chromomagnetic penguins(MP)and the NLO contributions to the form factors of Bs?P transitions.In the review section of this thesis,the author makes a brief review of the basic theoretical structures of B meson physics and presents an introduction for the popular factorization approaches being used in the calculation of the matrix elements of hadronic transitions,specially the PQCD factorization approach and the currently known next-to-leading order(NLO)contributions.The chapter 3,4 and 5 are the working part of the thesis.By employing the PQCD factorization approach,the author makes systematic calculations for the branching ratios,the CP-violating asymmetries and other physical observables of all Bs0?PP,PV,VV decays with the inclusion of all currently known NLO contributions,and we find the following points:(1)The effects of the NLO contributions on the PQCD predictions for the branch-ing ratios,CP asymmetries and other physical observables of the considered de-cay modes are channel dependent and will be tested by future experiments.For the measured decay modes,say Bs0?K0K0,K+K-,?'?',?-K*+,and and Bs0?K0K*0,K±K*T,?-k*+,and Bs0?K*0K*0,??,K*0?,the agreement between the PQCD predictions and the measured vales are improved effectively after the in-clusion of the NLO contributions.Take Bs0??-K*+as an example,when we define the ratio R1=B(Bs0??-K*+)exp/B(Bs0??-K*+)PQCD,we found that R1LO=0.52 is increased into W1NLO=0.83.In other words,the agreement between the theory and the measured values for the branching ratios B(Bs0??-K*+)is improved effectively after the inclusion of the NLO corrections?(2)For the CP asymmetries of Bs0?K+K-,? K*+ decays,and the longitudi-nal(transverse)polarization fractions fL(?),the relative phases(?4?,??)of Bs0???,K*0?,K*0K*0 decays,the NLO effects are actually small in size:say less than 50%.The NLO PQCD predictions for these physical observables do agree with those obtained based on other approaches,and also agree well with those currently available experimental measurements.Take the direct CP violation of Bs0??-K+decay as an example,the NLO PQCD prediction is ACP=(23.8-6.5+6.4)%,which is con-sistent with the QCDF prediction((20.7±-128+7.4)%)and SCET prediction((20±25)%),and also agree well with the measured value(27±4)%within the errors.(3)For other considered decays modes,the NLO PQCD predictions for the decay rates,CP violations and other physical observables considered in this paper are also basi-cally consistent with other theoretical predictions obtained based on rather different methods.The future precision measurements could help us to test or examine the differences among those rather different factoeization approaches.In chapter 6,the author gives a short summary for this thesis,and makes some discussions and the prospects for the future developments of the B meson physics.With the steady completion of different higher order corrections,the accuracy and reliability of the PQCD predictions will be improved efficiently.We do hope that our efforts can provide strong support to the analysis of the future huge amount of the data.