Heavy Meson To Light P-wave Meson Decay As Examples

The heavy to light meson exclusive decays play an important role in testing the standard model (SM), extracting its basic parameters, having a better understanding of the nonpertur-bative properties of QCD and searching for new physics beyond the SM. Compared with the inclusive ones, the exclusive decays are clean in experiments but difficult in theoretical calcu-lations due to the involvement of nonperturbative strong interactions. By using the effective hamiltonian methods, we can separate the perturbative contributions from the nonperturbative ones, which are contained in the Wilson coefficients and operator matrix elements respectively. The Wilson coefficients can be calculated by using the conventional perturbative theory, while the operator matrix elements come from nonperturbative effects and need to be dealt with by other methods. For the heavy hadrons (including mesons and baryons) containing one heavy quark (b or c), we can calculate the operator matrix elements in the framework of heavy quark effective field theory (HQEFT). In HQEFT, the operator matrix elements are expanded over 1/mQ (Q denotes the heavy quark) and thus the calculations are simplified obviously.This thesis is mainly devoted to studying the heavy to light P-wave axial vector meson exclusive decays by using the light cone sum rules in the framework of HQEFT, which includes:·The transition form factors:For semileptonic decays, there is only one meson in the final state and therefore the operator matrix elements can be parameterized into transition form factors. By using the light cone sum rules, we calculate the Dâ†'K1(including the spin triplet K1 A and the spin singlet K1B) transition form factors at the leading order of 1/mQ. We have considered the K1 meson light cone distribution amplitudes up to twist 3 and the SU(3) chiral symmetry breaking effects. Considering the large mass of K1, we believe that the transition form factors given by the light cone sum rules are reliable in the whole kinematically accessible region and data fitting is unnecessary. The uncertainties of transition form factors mainly come from the two free parameters, i.e. the D meson threshold energy s0 and the Borel transformation parameter T, which are about 5%-30%.·Studies on the heavy to light P-wave meson semileptonic decays: Based on the transition form factors given above, we study the Dâ†'K1(1270),K1(1400) semileptonic decays and calculate the corresponding branching ratios. It is found that the branching ratios for Dâ†'K1(1270) semileptonic decays are about 10-3, while the branching ratios for Dâ†' K1(1400) are smaller by two orders of magnitude. The uncertainties of branching ratios come from two aspects, one is the parameters S0, T and the other is K1(1270)-K1(1400) mixing angleθK1.Since the experimental values for the branching ratios of Dâ†'K1 semileptonic decays are absent, our results should be tested by more precise experiments in the future.