Testing time reversal invariance in exclusive semileptonic B meson decays

We demonstrate that polarization measurements in exclusive semileptonic B decays are powerful tools for unraveling non-standard model sources of T-violation. Measurements of the transverse polarization of the tau lepton in the B --> D tau<(nu)over bar> and B --> D*tau<(nu)over bar> decays probe separately effective scalar and pseudoscalar CP-violating four-Fermi interactions, whereas the D* polarization in the B --> D*l<(nu)over bar> (l = e, mu) decay is sensitive to an effective right-handed quark current interaction. Two T-odd polarization structures exist involving the D* polarization and they can be isolated and studied separately. An estimate of these T-odd effects is also given in the context of supersymmetric theories. (C) 1997 Elsevier Science B.V.