Study Of The Form Factor Of D Meson Decay

The study of D meson decay is significant for both the standard model and the CKM matrix,where the hadron matrix elements can be parameterized as form factors and thus accurately calculated.Currently,there are various ways to calculate the form factors,such as,QCD sum rules,light-cone sum rules,lattice QCD,heavy quark effective theory,low-energy effective theory,etc.The transfer momentum q²of in these methods is different.These form factors can be used to extract the CKM matrix elements,and also calculate the decay width,which in turn can be compared with experiments to give a good theoretical basis for experiments.In this paper,we calculate the form factors of the semileptonic decay process D?S,Al?_l(S denotes the scalar meson and A denotes the axial-vector meson,l=e,?)by applying the light-cone sum rules method.We study scalar mesons a₀(980)and a₀(1450)and take them as two-quark states,and study axial-vector mesons a₁(1260)and b₁(1235).Particularly,we introduce the chiral currents in the calculation,so that the form factors results include only the contribution of twist-2light-cone distribution amplitudes,which helps to avoid the uncertainty caused by the high twist distribution amplitudes.Otherwise,we obtain some simple relations between these form factors,which are similar to those obtained for the semileptonic decay process B?S,Al?_l.And the the form factors dependence on q²is plotted under the transfer momentum m_l² q²(m_D-m_M)²(M denotes the scalar meson and the axial-vector meson).Using the form factors,we calculate the decay branching ratios for the semilep-tonic decay process D?S,Al?_l.The numerical results of the branching ratios are not available experimentally,but the experimental product decay branching ratio and partial width ratios are given.Therefore,we further calculate the product decay branching ratio and partial width ratio to compare with the experimental data to verify the reliability of the results in this paper.Finally,we find that the result of D?a₀(980),b₁(1235)l?_lprocess agrees well with the experimental results within the error,while for D?a₀(1450),a₁(1260)l?_lprocess,it is expected that our theoretical predictions will be tested by experiments in the future,since the experiments do not have data yet.Further,we consider the initial state mesons as D_Smesons,calculate form factor and decay branching ratio of the D_s⁺?a₀⁰(980)l?_lprocess by using the light-cone sum rules with chiral currents,where the product branching ratio results are in good agreement with the recent experimental data of BES III.