D → P(π, K) helicity form factors within light-cone sum rule approach * * Supported in part by the National Science Foundation of China (11765007), the National Natural Science Foundation of China (11947302), the Project of Guizhou Provincial Department of Science and Technology (KY[2017]1089, No.KY[2019]1171) and the China Postdoctoral Science Foundation (2019TQ0329)

Abstract

In this study, helicity form factors (HFFs) are investigated by applying the QCD light-cone sum rule (LCSR) approach. The calculation accuracy is up to the next-to-leading order (NLO) gluon radiation correction of twist-(2,3) distribution amplitude. The resultant HFFs at a large recoil point are and , in which the contributions from the three particles of the leading order (LO) are so small that they can be safely neglected. The maximal contribution of the NLO gluon radiation correction for is less than 3%. After extrapolating the LCSR predictions for these HFFs to the whole -region, we obtain the decay widths for semileptonic decay processes , which are consistent with the BES-III collaboration predictions within error limits. After considering the -meson lifetime, we give the branching fractions of with ; our predictions also agree with the BES-III collaboration results within error limits, especially for the decay process. Finally, we present the forward-backward asymmetry and lepton convexity parameter , and further calculate the mean value of these two observations, and , which may provide a way to test those HFFs in future experiments.