The Calculations Of D?D_s To K* Transition Form Factors With Applications To Relevant Semileptonic Decays

The exclusive decays of hadrons play an important role in testing the standard model of particle physics,extracting its parameters and probe possible new physics.Due to the nonperturbative strong interactions involved,these decays have been always difficult in theoretical calculations.By using the method of effective Hamiltonian,we can separate the perturbative calculable short distance effects from the non-perturbative long distance effects,which are encoded by the Wilson coefficients and operator matrix elements respectively.The operator matrix elements can be expressed in terms of the transition form factors and decay constants via the approach of factorization.Calculating the transition form factors via light core sum rules need the light meson distribution amplitudes as inputs.Traditionally,the distribution amplitudes are obtained via the QCD sum rules.In recent years,M.Ahmady et.al.derived a set of new holographic AdS/QCD distribution amplitudes for the light vector mesons.Compared with the traditional distribution amplitudes given by QCD sum rules,the new distribution amplitudes contain more complete information about the quark momentum distribution in mesons.In the present thesis,based on the new holographic distribution amplitudes for K^*,we calculate the D_s?K^* transition form factors by using the light cone sum rules in full QCD and apply the results to relevant semileptonic decays.Firstly,we give an introduction to the mixing of D meson system,rare decays and semileptonic decays in chapter 2.In chapter 3,we describe the basic idea of the effective Hamiltonian and the process of calculating Wilson coefficients.In chapter 4,we introduce the light cone sum rules and illustrate the meson light cone distribution amplitudes.These three chapters are the review part of our thesis.Chapter 5is the work part.By using the new holographic distribution amplitudes for*K meson,we calculate the D_s?K^* transition form factors via the light cone sum rules in full QCD.Induced by the charged currents,the D?K^* transitions involve only four semileptonic form factors,i.e.A₁,A₂,A₀,V.The*KDs? decays can be generated by both the charged and flavor changing neutral currents and therefore involve three additional tensor form factors T₁,T₂,T₃.We compare our results with the form factors given via other approaches in the literature,including the LCSR based on traditional DAs,lattice simulation and quark models.Then we extract the CKM matrix element ||csV via the experimentally well measured semileptonic decays and .For thelsDlK n decay,we predict the branching ratio with comparison to current experiments.