CP Violation in ${\bar B}^0\to D^{*+}\mu^-{\bar\nu}_\mu$

Understand

In order to explain the observed anomalies in the measurements of $R_{D^{(*)}}$ and $R_{J/\psi}$, a variety of new-physics (NP) models that contribute to $b\to c\tau^-{\bar\nu}$ have been proposed.

• In this paper, we show how CP-violating observables can be used to distinguish these NP models.
• Because ${\vec p}_\tau$ cannot be measured (the decay products of the $\tau$ include the undetected $\nu_\tau$), obtaining the angular distribution of ${\bar B}^0\to D^{*+}\tau^{-}{\bar\nu}_\tau$ is problematic.
• Instead, we focus here on ${\bar B}^0\to D^{*+}(\to D^0 \pi^+)\mu^- {\bar\nu}_\mu$.