Radiative leptonic decays on the lattice

Abstract

Adding a hard photon to the final state of a leptonic pseudoscalar-meson decay lifts the helicity suppression and can provide sensitivity to a larger set of operators in the weak effective Hamiltonian. Furthermore, radiative leptonic $B$ decays at high photon energy are well suited to constrain the first inverse moment of the $B$-meson light-cone distribution amplitude, an important parameter in the theory of nonleptonic $B$ decays. We demonstrate that the calculation of radiative leptonic decays is possible using Euclidean lattice QCD, and present preliminary numerical results for $D_s^{+}\to {\ell }^{+}\nu \gamma$ and $K^{-}\to {\ell }^{-}\bar{\nu }\gamma$.

Comments: 7 pages, 5 figures, Proceedings of the 37th Annual International Symposium on Lattice Field Theory (Lattice 2019), June 16-22, Wuhan, China