τ polarization asymmetry in B→${\mathit{X}}_{\mathit{s}}$${\mathrm{\tau }}^{+}$${\mathrm{\tau }}^{\mathrm{-}}$

Rare B decays provide an opportunity to probe for new physics beyond the standard model. In this paper, we propose to measure the τ polarization in the inclusive decay B→${\mathit{X}}_{\mathit{s}}$ ${\mathrm{\tau }}^{+}$ ${\mathrm{\tau }}^{\mathrm{-}}$ and discuss how it can be used, in conjunction with other observables, to completely determine the parameters of the flavor-changing low-energy effective Hamiltonian. Both the standard model and several new physics scenarios are examined. This process has a large enough branching fraction, ∼few×${10}^{\mathrm{-}7}$, such that sufficient statistics will eventually be provided by the B factories currently under construction. © 1996 The American Physical Society.