The hadronic structure in τ → 3πν decays

Abstract

The hadronic structure of the decay of the τ lepton to three pions, τ → 3 πν τ , has been studied using DELPHI LEP-1 data. The invariant mass distributions of the 3π system have been fitted to the models of Kühn and Santamaria, Isgur Morningstar and Reader, and Feindt. The 3π and π + π − mass spectra are compared to the models. Qualitative agreement is observed at lower masses but for higher masses anomalous behaviour is observed, consistent with the existence of a hitherto unseen decay mode of the τ through a radial excitation of the α 1 meson.