Branching ratio estimates of tau(-) -> pi(-)eta(('))nu(tau) decays

We study the rare tau(-) -> pi(-)eta(('))nu(tau) decays. These processes occur via isospin violation and belong to the so-called second-class currents unseen in Nature so far. Our analysis is based on the framework of resonance chiral theory supplemented by dispersion relations. In this contribution we discuss the prospects for their discovery at forthcoming B-factories such Belle-II. While we find a total branching fraction for the pi(-)eta decay mode of similar to 1.7 x 10(-5), well within the reach of Belle-II, the pi(-)eta' channel might be one or two orders of magnitude more suppressed.