Studies Of The Transition Form Factors Of D,Ds To Light Tensor Mesons And Related Semileptonic Decays

The semileptonic decays of D,Ds mesons plays an unique role in the phenomenological study of particle physics,e.g.the extraction of |Vcs(d)|,exploration of the flavor structure relating to up type quarks.Due to the relative smaller mass of c quark in D,Ds,the calculation of nonperturbative QCD effects in exclusive decays is difficult and less attention is paid compared with corresponding B,Bs decays for a long time.In recent years,some noticeable deviations exist between the experimental values and SM predictions of several observables in B,Bs decays,which may imply new physics.Therefore,it is also valuable to perform similar investigations of D,Ds decays for the probing of new physics.The tensor mesons which can be viewed as the orbital excited states of vector mesons,contain more polarization information and are suitable to be used as a probe for the Lorentz structure of interactions.This thesis is mainly devoted to calculating the transition form factors of D,Ds to light P-wave tensor mesons a2(1320)、K2/(1430)、f2(1270)、f2’(1525)by using the light cone sum rules(LCSR)in the framework of heavy quark effective field theory(HQEFT)and investigating the relevant semileptonic decays on this basis.Firstly,we give a review on the charge current(CC)and flavor changing neutral current(FCNC)induced semileptonic decays of D,Ds mesons,respectively,including the theoretical framework and status of experiments.The research work of this thesis mainly includes two parts:1.The transition form factors of D,Ds to light P-wave tensor mesons are calculated in the framework of HQEFT by using LCSR and.The distribution amplitudes of tensor mesons are considered to twist-3 and the series expansion parameterization is adopted in the fitting of form factors.The magnitudes of our form factors are similar to those given by ISGW quark model and LFQM,while the results of LCSR in full QCD are noticeably larger.2.With the form factors given here,we studied the relevant CC and FCNC induced semileptonic decays separately,predicting the branching ratios,longitudinal polarization fractions and forward backward asymmetries.It is found that the branching ratios of D→Tlvl(l=e、μ)are at the order of 10-7-10-6,the longitudinal polarization fractions are about(75-80)%and the zero-crossing points of forward backward asymmetries have no significant change for different decay modes.For the semileptonic decays induced by FCNC,it is shown that the branching ratios of D、Ds→Tl+l-(l=e、μ)are at the order of 10-9,the longitudinal polarization fractions are about(70-80)%and there is no zero-crossing points of forward backward asymmetries.These results may be tested by more precise experiments in the future.