  Recent experimental results for the ratios of the branching fractions of the
decays $\bar{B} \to D^{(*)} \tau \bar\nu$ and $\bar{B} \to D^{(*)} \mu \bar\nu$
came as a surprise and lead to a discussion of possibility of testing New
Physics beyond the Standard Model through these modes. We show that these decay
channels can provide us with good constraints on New Physics and several New
Physics cases are favored by the present experimental data. In order to
discriminate various New Physics scenarios, we examine the $q^2$ distributions
and estimate the sensitivity of this potential measurement at the
SuperKEKB/Belle II experiment.
