$b\to c\tau {\bar{\nu }}_{e,\mu }$ contributions to $R(D^{(\ast )})$

Shikma Bressler, Federico De Vito Halevy, Yosef Nir

The $R(D^{(\ast )})$ puzzle stands for a $\sim 3\sigma$ violation of lepton flavor universality between the decay rates of $B\to D^{(\ast )}\tau \nu$ and $B\to D^{(\ast )}\ell \nu$, where $\ell =e,\mu$. If it i…