https://doi.org/10.1140/epjc/s10052-015-3583-6
Regular Article - Theoretical Physics
Radiative leptonic 
decay in effective field theory beyond leading order
1
INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
2
State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China
* e-mail: rlzhu@sjtu.edu.cn
Received:
6
April
2015
Accepted:
27
July
2015
Published online:
8
August
2015
We study the radiative leptonic 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 
, but also the nonrelativistic corrections at the order 
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 
. For phenomenological application, we present our results for the photon energy, lepton energy and lepton-neutrino invariant mass distribution.
© The Author(s), 2015
