## Semileptonic B{yields}{pi} decays from an Omnes improved nonrelativistic constituent quark model

The semileptonic B{yields}{pi}l{sup +}{nu}{sub l} decay is studied starting from a simple quark model which includes the influence of the B* pole. To extend the predictions of a nonrelativistic constituent quark model from its region of applicability near q{sub max}{sup 2}=(m{sub B}-m{sub {pi}}){sup 2} to all q{sup 2} values accessible in the physical decay, we use a novel multiply subtracted Omnes dispersion relation, which considerably diminishes the form-factor dependence on the elastic {pi}B{yields}{pi}B scattering amplitudes at high energies. By comparison to the experimental branching fraction we extract |V{sub ub}|=0.0034{+-}0.0003(exp){+-}0.0007(theory). To further test our framework, we also study D{yields}{pi} and D{yields}Kmore »