Lepton mass effects in semi-leptonic B-meson decays

We calculate decay rates, decay spectra and polarization parameters for exclusive semi-leptonic (s.l.) b-->c and b-->u bottom meson and free bottom quark decays involving the τ-lepton. These are compared to the corresponding observables calculated for the light lepton modes. A surprising feature is a significant scalar current contribution in s.l. B-->D and B-->π decays which leads to an average positive longitudinal τ-polarization in the B-->D mode.

Supported by Bundesministerium für Forschung und Technologie, 05 4HH 92P/3, Bonn, RFG.