G-parity breaking contributions in τ − → η (′) π − ντ decays induced at one loop level by the anomalous γγη (′) vertices

Abstract

Second class current processes (SCC) are forbidden in the limit of exact isospin symmetry by G-parity. Since G-parity invariance is slightly broken by the u–d mass difference and electromagnetic effects, SCC can appear but they are naturally suppressed. τ ⁻ → η ^(′) π ⁻ ν_τ decays represent a clean test of SCC and according to theoretical estimations and thanks to the increased luminosity contemplated at the Belle-II collaboration, their discovery should be finally possible. Consequently, a careful evaluation of G-parity breaking contributions results mandatory in order to isolate possible new physics contributions. In this work, we evaluate the G-parity breaking contributions in τ ⁻ → η ^(′) π ⁻ ν_τ decays induced at one loop level by the anomalous electromagnetic γγη ^(′) vertices.