Revisiting the new-physics interpretation of the $b\to cτν$ data
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Revisiting the new-physics interpretation of the $b\to cτν$ data

  • Author(s): Shi, Rui-Xiang
  • Geng, Li-Sheng
  • Grinstein, Benjamín
  • Jäger, Sebastian
  • Camalich, Jorge Martin
  • et al.
Abstract

We revisit the status of the new-physics interpretations of the anomalies in semileptonic $B$ decays in light of the new data reported by Belle on the lepton-universality ratios $R_{D^{(*)}}$ using the semileptonic tag and on the longitudinal polarization of the $D^*$ in $B\to D^*\tau\nu$, $F_L^{D^*}$. The preferred solutions involve new left-handed currents or tensor contributions. Interpretations with pure right-handed currents are disfavored by the LHC data, while pure scalar models are disfavored by the upper limits derived either from the LHC or from the $B_c$ lifetime. The observable $F_L^{D^*}$ also gives an important constraint leading to the exclusion of large regions of parameter space. Finally, we investigate the sensitivity of different observables to the various scenarios and conclude that a measurement of the tau polarization in the decay mode $B\to D\tau\nu$ would effectively discriminate among them.

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