The current world averages of the ratios $R_{ D^{ (*)}}$ are about $4\sigma$ away from their Standard Model prediction. These measurements indicate towards the violation of lepton flavor universality in $b\rightarrow c\,l\,\bar{ \nu}$ decay. The different new physics operators, which can explain the $R_{ D^{ (*)}}$ measurements, have been identified previously. We show that a simultaneous measurement of the polarization fractions of $\tau$ and $D^*$ and the angular asymmetries $A_{ FB}$ and $A_{ LT}$ in $B\rightarrow D^*\tau\bar{ \nu}$ decay can distinguish all the new physics amplitudes and hence uniquely identify the Lorentz structure of new physics.
Categories: hep-ph hep-ex