## Abstract

In order to explain the observed anomalies in the measurements of \( {R}_{D^{\left(\ast \right)}} \) and *R*_{J/ψ}, a variety of new-physics (NP) models that contribute to \( b\to c{\tau}^{-}\overline{\nu} \) have been proposed. In this paper, we show how CP-violating observables can be used to distinguish these NP models. Because \( {\overrightarrow{p}}_{\tau } \) cannot be measured (the decay products of the *τ* include the undetected *ν*_{τ}), obtaining the angular distribution of \( {\overline{B}}^0\to {D}^{\ast +}{\tau}^{-}{\overline{\nu}}_{\tau } \) is problematic. Instead, we focus here on \( {\overline{B}}^0\to {D}^{\ast +}\left(\to {D}^0{\pi}^{+}\right){\mu}^{-}{\overline{\nu}}_{\mu } \). This process may also receive contributions from the same NP, and LHCb intends to measure the CP-violating angular asymmetries in this decay. There are two classes of NP models that contribute to \( b\to c{\mu}^{-}{\overline{\nu}}_{{}_{\mu }} \). These involve (i) a *W*^{′} (two types) or (ii) a leptoquark (LQ) (six types). The most popular NP models predict no CP-violating effects, so the measurement of nonzero CP-violating asymmetries would rule them out. Furthermore these measurements allow one to distinguish the *W*^{′} and LQ models, and to differentiate among several LQ models.

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Bhattacharya, B., Datta, A., Kamali, S. *et al.* CP violation in \( {\overline{B}}^0\to {D}^{\ast +}{\mu}^{-}{\overline{\nu}}_{\mu } \).
*J. High Energ. Phys.* **2019**, 191 (2019). https://doi.org/10.1007/JHEP05(2019)191

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DOI: https://doi.org/10.1007/JHEP05(2019)191

### Keywords

- Beyond Standard Model
- CP violation