Exact Light-Cone Wavefunction Representation of Matrix Elements of Electroweak Currents

The matrix elements of electroweak currents which occur in exclusive decays of heavy hadrons are evaluated in the nonperturbative light-cone Fock representration. In general, each semileptonic exclusive decay amplitude receives two contributions, a diagonal ∆n = 0 parton-number-conserving amplitude and a ∆n = −2 contribution in which a quark and an antiquark from the initial hadron Fock state annihilate to the leptonic current. The general formalism can be used as a basis for systematic approximations to heavy hadron decay amplitudes such as hard perturbative QCD contributions. We illustrate the general formalism using a simple perturbative model of composite hadrons. Our analysis demonstrates the occurence of “zero-mode” endpoint contributions to matrix elements of the “bad” j currents in the Drell-Yan frame when q → 0. (Submitted to Physics Letters B.) ∗Work supported by the Department of Energy, contract DE–AC03–76SF00515.