Polarization measurements andTviolation in exclusive semileptonicBdecays

We provide a general analysis of time reversal invariance violation in the exclusive semileptonic $B$ decays $B\to D\mathcal{l}\overline{\nu }$ and $B\to D^{*}\mathcal{l}\overline{\nu }$. Measurements of the lepton and $D^{*}$ polarizations can be used to search for and identify nonstandard model sources of $T$ violation. Upper limits are placed on the $T$-odd polarization observables in both the supersymmetric $R$-parity-conserving and $R$-parity-breaking theories, as well as in some nonsupersymmetric extensions of the standard model, including multi-Higgs-doublet models, leptoquark models, and left-right symmetric models. It is noted that many of these models allow for large $T$-violating polarization effects which could be within the reach of the planned $B$ factories.