Second class current effects in Tau-Lepton decay

The matrix element for the G-parity nonconserving decay τ → η+π+ντ is calculated in the standard electroweak theory. The ηπ final state is assumed to be dominated by the a0(980) resonance, which is described by an excited anti qq state of the MIT bag model. The branching ratio B(τ → η+π+ντ), while quite model dependent, is very small (< 10-4) for all reasonable values of the bag radius and quark masses. Consequently, the decay mode is a negligible background in τ decay and can be ruled out as being responsible for the 'missing' one-prong events in τ decay. (orig.)