  In this paper we study the semileptonic decay $B\to\pi l \nu$ and in
particular the factorizable contribution to symmetry breaking corrections to
the form factors at large recoil. This contribution is a convolution of the
coefficient function, which can be calculated in perturbation theory, and of
the nonperturbative light-cone distribution amplitudes of the mesons. The
coefficient function, in turn, can also be represented as convolution of the
hard Wilson coefficient and of the jet function. Loop corrections to the hard
Wilson coefficient and jet function are calculated. We use the method of
expanding by regions to calculate these corrections. The results obtained
coincide with the ones calculated in the framework of the soft-collinear
effective theory (SCET). Factorization of soft and collinear singularities into
the light-cone distribution amplitudes is demonstrated at one-loop level
explicitly. It is also demonstrated that the contribution of the so-called
soft-messenger modes vanishes; this fact is of critical importance to the
factorization approach to this decay.
