Angular Analysis of New Physics Operators in polarized $\tau \to 3 \ell$ Decays

TL;DR

This paper explores how the polarization and angular distribution in rare tau decays can help identify new physics operators, using a phenomenological approach with virtual experiments to estimate the required event numbers.

Contribution

It introduces the use of tau polarization and angular observables in analyzing lepton-flavor violating decays to better probe effective new physics operators.

Findings

Polarization and angular observables enhance sensitivity to new physics.

Estimated event counts needed for operator coefficient extraction.

Focus on integrated observables due to decay rarity.

Abstract

In a bottom-up approach we investigate lepton-flavour violating processes $\tau \to 3 \ell$ that are mediated by New Physics encoded in effective-theory operators of dimension six. While the opportunity to scrutinize the underlying operator structure has been investigated before, we explore the benefits of utilising the polarization direction of the initial $\tau$ lepton and the angular distribution of the decay. Given the rarity of these events (if observed at all), we focus on integrated observables rather than spectra, such as partial rates and asymmetries. In an effort to estimate the number of events required to extract the coupling coefficients to the effective operators we perform a phenomenological study with virtual experiments.