Radiative Corrections to the Decay $B\to \pi e\nu$ and the Heavy Quark Limit

We calculate radiative corrections to the light-cone sum rule for the semileptonic form factor in $B\to\pi e\nu$ decays and thus remove the major uncertainty in determining the CKM mixing angle $|V_{ub}|$ by this method. We discuss the remaining uncertainties and perspectives for further studies. The structure of the radiative corrections suggests factorization of soft (end-point) and hard rescattering contributions in heavy-to-light decays in the heavy quark limit.