Generalized structure functions in semileptonic tau decays

TL;DR

This paper generalizes the structure functions for tau decays to include potential tensor interactions beyond the Standard Model, emphasizing the importance of spectral functions for CP and T violation studies.

Contribution

It introduces a new framework for structure functions in tau decays that accounts for tensor interactions, extending previous models.

Findings

Generalized structure functions accommodate tensor interactions.

Spectral functions are crucial for model-independent CP and T violation analysis.

Highlights the importance of measuring these spectral functions in tau decays.

Abstract

In case there are tensor interactions beyond the SM in the low-energy effective Lagrangian, their interference with the SM V-A currents yields a contribution for tau decays into three or more mesons that cannot be included in the famous structure functions introduced by K\"uhn and Mirkes in their seminal 1992 paper. We present this generalization here, highlighting again the importance of measuring the (generalized) spectral functions, as being model-independent and exploiting maximally the data. This can be particularly relevant for CP and T violation studies with at least three mesons in the final state of the tau decay.