Factorization in leptonic radiative B→γeν decays

We discuss factorization in exclusive radiative leptonic B --> gammaev decays using the soft-collinear effective theory. The form factors describing these decays can be expanded in a power series in Lambda(QCD)/Egamma with Egamma the photon energy. We write down the most general operators in the effective theory which contribute to the form factors at leading order in Lambda(QCD)/Egamma, proving their factorization into hard, jet and soft contributions, to all orders in a, (C) 2002 Published by Elsevier Science B.V.