The Full $B \to D^{*} \tau^{-} \bar{\nu_\tau}$ Angular Distribution and CP violating Triple Products

Abstract

We perform a comprehensive study of the impact of new-physics operators with different Lorentz structures on $\BDstarellnu$ decays, $(\ell = e, \mu, \tau $) involving the $b \to c l \nu_\ell$ transition. We present the full three angle and $q^2$ angular distribution with new physics operators with complex couplings. Various observables are constructed from the angular distribution with special focus on the CP violating triple product asymmetries which vanish in the Standard Model without any hadronic complications. Two of the three triple products are only sensitive to vector/axial vector new physics operators. %and do not depend on pseudoscalar new physics. Hence, the measurements of non-zero triple-product asymmetries will be a clear sign of new physics and a strong signal for vector/axial vector new physics operators. Even though we focus on $\tau$ final state, one can use the triple-products to search for new physics with $e$ and $\mu$ in the final state.