On meson dominance in the `second class' tau \to eta pi nu_tau decay

TL;DR

This paper evaluates the tau to eta pi nu_tau decay process, considering contributions from both ground state and excited mesons to improve the accuracy of branching ratio estimates.

Contribution

It introduces a comprehensive assessment including radial excitations rho(1450) and a_0(1450) in the meson dominance model for the decay.

Findings

Radial excitations significantly affect the decay's form factors.

Branching ratio estimates are refined by including excited meson states.

The approach enhances understanding of isospin-violating tau decays.

Abstract

Motivated by recent estimates of the isospin-violating process tau \to eta pi nu_tau, mostly relying on the rho and a_0 dominance of the relevant form factors near threshold, we present an assessment for the branching ratio that accounts for additional, potential, effects from the lowest radial excitations rho(1450) and a_0(1450), respectively, also lying in the decay phase space.