| This thesis is devoted to calculating the heavy to light axial meson transition form factors via the light cone sum rules in the framework of heavy quark effective field theory and applying the results to study the corresponding exclusive semileptonic decays.In the review part,we give an introduction to the basic theoretical framework and relevant backgrounds involved in the research,including two aspects,i.e.the standard model of particle physics?the electroweak theory and quantum chromodynamics?QCD??and the quark model for mesons?with emphasis on the basic properties of axial vector mesons?.In the research part,we firstly calculate the transition form factors of D to light axial mesons a1?1260?,f1?1285?,f1?1420?,b1?1235?,h1?1170?,h1?1380? by using the light cone sum rules in the framework of heavy quark effective theory.In the calculations,we consider the light cone distribution amplitudes of light axial mesons to twist 3.For the two free parameterss0and T,the allowed regions are determined by requiring the sum rules to be most stable.The uncertainties stemming from these two parameters are analyzed.Based on the transition form factors given here,we study the corresponding exclusive semileptonic decays,predicting the observables such as the differential decays rates,branching fractions andsoon.Itisfoundthatthebranchingfractionsof D?f1?1420?lv1 and D?h1?1380?lv1 are smaller than those of D?f1?1285?lv1 and D?h1?1170?lv1 by about two order of magnitude,respectively.The branching fractions of D?a1?1260?lv1 and D?b1?1235?lv1 are at the order ofO(10-4)andthe branching fractions of decay modes with a charged axial vector meson in the final states are smaller than the corresponding decay modes with a neutral axial vector meson in the final states.These results can be tested by more precise experiments such as LHCb,BelleII in the future,which provide some references for testing the standard model of particle physics and searching for possible new physics signals. |
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