B => π π ell ν decays in a QCD relativistic potential model

In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decay B => \pi\pi \ell \nu. The calculation is performed in a phase space region far away from the resonances and therefore is complementary to other decay mechanisms where the pions are produced by intermediate particles, e.g. in the chiral approach. We give an estimate of the contribution of the non resonant channel of the order of BR(B- => \pi+ \pi- \ell \nu) \approx 2.2 x 10^(-4).