Semileptonic tau decays beyond the Standard Model

TL;DR

This paper analyzes semileptonic tau decays to explore potential new physics beyond the Standard Model by deriving likelihood functions for Wilson coefficients from experimental data and theoretical models.

Contribution

It provides a comprehensive, model-independent likelihood analysis of Wilson coefficients in tau decays, incorporating recent measurements and theoretical advances.

Findings

Likelihood functions for Wilson coefficients derived from tau decay data

Identification of new physics hints related to the Cabibbo anomaly

Framework for combining tau decay data with other low-energy observables

Abstract

Hadronic $\tau$ decays are studied as probe of new physics. We determine the dependence of several inclusive and exclusive $\tau$ observables on the Wilson coefficients of the low-energy effective theory describing charged-current interactions between light quarks and leptons. The analysis includes both strange and non-strange decay channels. The main result is the likelihood function for the Wilson coefficients in the tau sector, based on the up-to-date experimental measurements and state-of-the-art theoretical techniques. The likelihood can be readily combined with inputs from other low-energy precision observables. We discuss a combination with nuclear beta, baryon, pion, and kaon decay data. In particular, we provide a comprehensive and model-independent description of the new physics hints in the combined dataset, which are known under the name of the Cabibbo anomaly.