"Old" resonance model for 3π decays of K and η

Abstract

In view of the current experimental interest in the three-pion modes of K and η decays, a phenomenological model of a π-π resonance in I = 0, proposed several years ago by one of us, is re-examined in the context of the present experimental data. It is found that the model satisfactorily explains all the available features of τ and τ' decays if the resonance occurs at an energy around 400 MeV with a width 85-90 MeV. The corresponding parameters with a somewhat smaller width (˜75-80 MeV) also give satisfactory agreement with the experimental results for η decay. This model corresponds to a repulsive I = 0 π-π interaction at low energies and is therefore not in disagreement with the earlier dispersion theoretical predictions for τ decay, using final-state interactions. It also has a strong resemblance to the s model of Brown and Singer.