Exclusive semileptonic decays of heavy mesons

Abstract

Exclusive semileptonic decays of heavy mesons provide interesting information on systems consisting of quarks of unequal mass. We express the formfactors of the hadronic current in terms of relativistic bound state wave functions for which we take the solutions of a relativistic harmonic oscillator potential. The wave function overlap is determined by the quark mass dependent longitudinal momentum distribution and differs from results based on non relativistic wave functions. The semileptonic widths and lepton spectra are calculated using in addition nearest pole dominance for the momentum transfer dependence of the formfactors. We compare our results with recent experimental data. The formfactor calculation also allows an estimate of special nonleptonic transitions. From the CLEO results on$\bar B^0 \to \pi ^ + \pi ^ -$ and$\bar B^0 \to D^{* + } + \pi ^ -$ we find for the corresponding Kobayashi-Maskawa matrix element ratio the limit |V _ub /V _cb |≲0.3.