Studies On Exclusive Decays Of B、B_s To Light Tensor Mesons

The exclusive decays of B_（s）to light mesons play an important role in the phenomenological study of particle physics.Up to now,extensive analyses have been carried out on the processes containing only S-wave mesons in the final states both theoretically and experimentally.In contrast,there is relatively little research on the processes involving high orbital excited mesons（P-wave mesons,D-wave mesons,...）.In this thesis,we mainly calculate the transition form factors of B_（s）to light tensor mesons（including P-wave and D-wave tensor mesons）by the light cone sum rules（LCSRs）in the framework of heavy quark effective field theory（HQEFT）,and then investigate the relevant exclusive semileptonic decays.In the theoretical review part,we first give a brief introduction to the flavor structure of the standard model of particle physics（SM）and its existing problems;then we give a detailed introduction to the current experimental s-tatus of B_（s）exclusive rare decays and the quark model of mesons.The research work of this thesis mainly includes two parts:1.the investigation of B_（s）to 2++light tensor mesons（a2（1320）,K2*（1430）,f2（1270）,f2’（1525））rare decays.We first give a complete set of transition form factors in the framework of HQEFT,including the tensor type form factors used in the study of rare decays,and compare them with the results via other methods in the pre-vious literature.Generally speaking,the form factors given here is slightly larger than the results given by pQCD and QCD sum rules,but it is still compatible with them.Using the form factors given in this thesis,we investi-gate the rare decays of B_（s）to 2++light tensor mesons,predicting the branching ratios,longitudinal polarization fractions and forward backward asymmetries.It is found that the branching ratios of B_（s）→Tl＋l-with l=e,μare at the order of 10-8-10-7,while those for the decays with l=τ are smaller by three orders of magnitude.The longitudinal polarization fractions are about（40-70）%.The zero crossing points of forward backward asym-metries for different decay modes have no significant change.2.In the framework of HQEFT,the form factors of B_（s）to 2--light tensor meson K2（1820）are calculated by using LCSRs,and the relevant semileptonic decay Bs→ K2（1820）lv-l is studied.It is found that the branching ratios are at the order of 10-4,the results for decay modes with l=τ are about 1/4 of those for l=e,μ.The corresponding longitudinal polarization fractions are about（60-70）%.The zero crossing points of forward backward asymmetries for different decay modes varies significantly.