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 non-perturbative light-cone Fock representation. In general, each semileptonic exclusive decay amplitude receives two contributions, a diagonal Δn = 0 parton-number-conserving amplitude and a Δn = −2 contribution in which a qaurk 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 occurrence of “zero-mode” endpoint contributions to matrix elements of the “bad” j− currents in the Drell-Yan frame when q+ → 0.