helicity form factors and the decays *

Abstract

Abstract In this paper, we calculate the helicity form factors (HFFs) up to twist-4 accuracy by using the light-cone sum rules (LCSR) approach. After extrapolating those HFFs to the physically allowable region, we investigate the -meson two-body decays and semi-leptonic decays , where stand for light pseudoscalar and vector mesons, respectively. The branching fractions can be derived using the CKM matrix element and the lifetime from the Particle Data Group, and we obtain , , , , and . We then obtain and , which agree with the LHCb measured value within -error. We also obtain , which like other theoretical predictions, is consistent with the LHCb measured value within -error. These imply that the HFFs under the LCSR approach are also applicable to the meson two-body decays and semi-leptonic decays , and the HFFs obtained using LCSR in a new way implies that there may be new physics in the semi-leptonic decays.