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

TL;DR

This paper analyzes the full angular distribution of B to D* tau nu decays, focusing on CP violation and new physics effects, especially through triple product asymmetries sensitive to vector and axial-vector operators.

Contribution

It provides the complete angular distribution including complex new physics couplings and identifies CP-violating observables that can signal new physics beyond the Standard Model.

Findings

Triple product asymmetries vanish in the Standard Model.

Non-zero triple products indicate vector/axial-vector new physics.

Method applicable to e and mu final states for new physics searches.

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.