New physics in the weak interaction of $\bar B\to D^{(*)}\tau\bar\nu$

TL;DR

This paper investigates potential new physics in semi-tauonic B decays by analyzing general four-Fermi interactions, identifying observables that distinguish different models, and assessing specific new physics scenarios against experimental deviations.

Contribution

It provides a model-independent framework for analyzing B decay anomalies and evaluates the viability of various new physics models in explaining experimental results.

Findings

Two Higgs doublet models without FCNC are unlikely to explain data.

Models with FCNC or leptoquarks can accommodate experimental deviations.

Correlations among polarization observables help distinguish new physics operators.

Abstract

Recent experimental results on exclusive semi-tauonic B meson decays, B -> D(*) tau nu, showing sizable deviations from the standard model prediction, suggest a new physics in which the structure of the relevant weak charged interaction may differ from that of the standard model. We study the exclusive semi-tauonic B decays in a model-independent manner using the most general set of four-Fermi interactions in order to clarify possible structures of the charged current in new physics. It turns out that correlations among observables including tau and D* polarizations and q^2 distributions are useful to distinguish possible new physics operators. Further, we investigate some interesting models to exhibit the advantage of our model-independent analysis. As a result, we find that two Higgs doublet models without tree-level FCNC and the minimal supersymmetric standard model with R-parity violation are unlikely to explain the present experimental data, while two Higgs doublet models with FCNC and a leptoquark model are consistent with the data.