On the branching ratio of the "second class" tau --> eta' pi nu_tau decay

TL;DR

This paper estimates the standard model prediction for the tau decay into eta' pi nu_tau, finding it significantly below experimental limits and highlighting potential for discovering new physics with higher statistics.

Contribution

It provides a detailed theoretical estimate of the branching ratio using meson dominance and mixing effects, suggesting room for new interactions beyond the standard model.

Findings

Predicted branching ratio is an order of magnitude below current experimental limits.

The model incorporates pi^0-eta-eta' mixing effects.

Results suggest potential for observing new physics in high-statistics experiments.

Abstract

We present an assessment of the standard model expectations for the branching ratio of the isotopic spin and G-parity violating decay tau --> eta' pi nu_tau. The estimate is based on a vector and scalar meson dominance parametrization of the relevant form factors, that explicitly accounts for pi^0-eta-eta' mixing. The numerical results obtained in this framework indicate a branching ratio one order of magnitude (or more) below the current experimental limit, and suggest the possibility of evidencing some novel interaction in high statistics studies of this decay.