Isospin violation in τ → 3πντ

Abstract

Isospin violating signals in the τ− → (3π)−ντ decay mode are discussed. For the τ− → π−π−π+ντ decay mode, isospin violation arises from the vector current contribution in the τ− → ωπ−ντ decay with the subsequent isospin violating ω decay into π+π−. We demonstrate that such effects may be observed in presently available data through the measurement of the interference effects of these vector current contributions with the dominating axial vector current,i. e. through a measurement of the structure functionsW F, WG, WH andW I. In the case of the τ− → π0π0π−ντ decay mode, a vector current contribution is generated by ηπ0 mixing in the decay chain τ− → ηϱ−ντ → π0π0π−ντ. We find that this effect is rather small, the magnitude of the associated interference terms being too low for present statistics.