Radiative leptonic Bc decays in effective field theory

The recent discovery of the Bc meson by the CDF Collaboration and proposed new experiments at Fermilab and CERN motivate new theoretical studies of the Bc system. Here we investigate the radiative leptonic decay Bc→γlν. This process is an important background to the annihilation process Bc→lν, which will be used to extract the Bc decay constant. We perform a model-independent calculation, based on QCD, of the partial width and various kinematic distributions. We also examine the decay within the framework of NRQCD, an effective field theory of nonrelativistic quarks, generalizing the NRQCD Lagrangian to include external sources for the weak and electromagnetic currents. Finally, we will show how NRQCD reproduces the correct position of the Bc* pole in the emission of very soft photons. copyright 1999 The American Physical Society