Studies On D, D_s To Light Meson Semileptonic Decays

D,Ds to light meson semileptonic decays play an important part in checkout the parame-ters(such as the CKM matrix elements|VCS|,|Vcd|) of standard model(SM),having received great attention for deeply understanding of non-perturbation effect of quantum color dynamics (QCD). In the process of study semileptonic decays,we must take into account the non-perturbation ef-fect of strong interactions. But the process will be troublesome because of involving the non-perturbation. By using the effective hamiltonian methods,separating the perturbation contribu-tion from the non-perturbation effect,which are contained in the Wilson coefficients and operator matrix elements respectively. Using the conventional perturbation theory calculates the Wilson coefficients,while the operator matric elements come from non-perturbation effects and need to use another method to deal with. For D,Ds meson containing one heavy quark(c quark),we can use the heavy quark effective field theory(HQEFT)to research the decay. In order to simplify the calculation,we can expand the operator matrix elements over the reciprocal of heavy quark mass.This thesis is mainly devoted to studying heavy quark expansion to next leading order (NLO) for D,Ds to light meson semileptonic decays in the framework of HQEFT, Including theoretical overview and specific work of two parts.In the theoretical overview section,we introduce the basic framework and content of the standard model of particle physics,the effective hamiltonian method and the heavy quark effective field theory. This is the basis for us to carry out specific work.In the specific work section,we mainly investigate the semileptonic decay D→K*lv and Ds→(?)lv via heavy quark expansion to next leading order (NLO) in the framework of HQEFT. We calculate D→K*lv、Ds→(?)lv transition form factors A1,A2,A3,V by using the light cone sum rules. For the contribution of heavy quark expansion to leading order (LO),we have considered K*,(?) meson light cone distribution amplitudes up to twist4;for the contribution to next leading order (NLO),we have considered K*,(?) meson light cone distribution amplitudes up to twist2. Calculations show that the contributions from heavy quark expansion to next leading order is different for different transition form factors,around22%(Ds→(?)) of the leading or-der. Taking into account the contribution of heavy quark expansion to next leading order (NLO),in heavy quark expansion to leading order (LO) transition form factor considering the high-twist light meson distribution amplitudes smaller than R2=A2(0)/A1(0) problem has been signifi- cantly improved. On this basis,we calculated the branching ratios of corresponding semileptonic decay process D0→K*-l+v、D+→K*0l+v and Ds→(?)lv. The first two processes agree well with the current experimental data.The last process is consistent with experiments within the uncertainties.