New physics effects on $B\to D^{(*)}\tau\nu$ decays

TL;DR

This paper explores potential new physics influences on B meson decays involving tau leptons, using a model-independent approach to constrain Wilson coefficients and analyze polarization effects, with implications for high-energy scales up to 27 TeV.

Contribution

It provides a comprehensive, model-independent analysis of new physics effects on B to D(*) tau nu decays, including constraints and polarization predictions.

Findings

New physics scale constrained up to ~27 TeV.

Tau polarization asymmetry can be negative only for specific operators.

Constraints from Bc→τν limit new physics contributions.

Abstract

We investigate new physics effects on $B\to D^{(*)}\tau\nu$ decays in a general and model-independent way. The $\chi^2$ fits for fractions of the branching ratios $R(D^{(*)})$ and other polarization parameters are implemented. We parameterize the relevant Wilson coefficients with a new physics scale and its power together with combined fermionic couplings. Constraints from $B_c\to\tau\nu$ are imposed such that its branching ratio is less than 30%. For a moderate range of our parameters we find that the new physics scale goes up to $\lesssim 27$ TeV for ordinary new particle contributions. It turns out that the polarization asymmetry of $\tau$ for $B\to D$ transition can be negative only for a few combinations of the new physics operators. We also discuss related processes $B_c\to J/\Psi\tau\nu$ and $\Lambda_b\to\Lambda_c\tau\nu$ decays.