Radiative leptonic Bc→γℓν¯ decay in effective field theory beyond leading order

We study the radiative leptonic Bc→γℓν¯ decays in nonrelativistic QCD effective field theory, and we explore the contribution from a fast-moving photon. As a result, interactions between the photon and the heavy quarks can be integrated out, resulting in the factorization formula for the decay amplitude. We calculate not only the relevant short-distance coefficients at leading order and next-to-leading order in αs , but also the nonrelativistic corrections at the order |v|2 in our analysis. We find that the QCD corrections can significantly decrease the branching ratio, and this is of great importance in extracting the long-distance operator matrix elements of Bc . For phenomenological application, we present our results for the photon energy, lepton energy and lepton-neutrino invariant mass distribution