2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189165We use a multiply-subtracted Omnes dispersion relation for the form factor f^+ in B->pi semileptonic decay, allowing the direct input of experimental and theoretical information to constrain its dependence on q^2. Apart from these inputs we use only unitarity and analyticity properties. We obtain |V(ub)|=(4.02 \pm 0.35)\times 10^{-3}, improving the agreement with the value determined from inclusive methods, and competitive in precision with them.10 pages, 4 figures. We include experimental data from BaBar (hep-ex/0607089). Approved for publication in PRDHigh Energy Physics - PhenomenologyHigh Energy Physics - Latticetext