$\tau^-\to\pi^-\eta^{(\prime)}\nu_\tau$ decays

The vector and scalar form factors relevant to the second-class current $\tau^-\to\pi^-\eta^{(\prime)}\nu_\tau$ processes are evaluated supplementing Chiral Perturbation Theory with the inclusion of resonances as explicit degrees of freedom. While the vector contribution is essentially fixed from knowledge of the two-pion vector form factor, the scalar form factor demands a coupled channel dispersive analysis to obtain robust predictions for the detection of these decay modes.