Probing New Physics with $q^2$ distributions in $\bar{B} \to D^{(*)} \tau \bar\nu$

TL;DR

This paper explores how $q^2$ distributions in $ar{B} o D^{(*)} au ar u$ decays can be used to test for New Physics beyond the Standard Model, especially with upcoming Belle II data.

Contribution

It demonstrates the potential of $q^2$ distributions to distinguish various New Physics scenarios in $ar{B}$ decays, providing a new method for probing beyond Standard Model physics.

Findings

Current data favors several New Physics models.

$q^2$ distributions can effectively discriminate between New Physics scenarios.

Belle II has high sensitivity for these measurements.

Abstract

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.