Hadronic decays of $\tau$ lepton provide a unique possibility to study dynamics in a three-body hadronic system. Particularly, $\tau^-\to \pi^+\pi^-\pi^-\,\nu$ and $\tau^-\to K^-K^+\pi^-\,\nu$ gives a clear sample of the $a_1(1260)$ decays. While the pionic system is dominated by the $\rho$ intermediate resonance and the system with kaons shows mostly $K^*$ resonances, the two final states are strongly coupled via the scalar sector and $\pi^+\pi^- \leftrightarrow K^+K^-$ transitions. In the talk, I will discuss the consequences of this coupling as a modification of the resonance lineshapes and an appearance of the observable triangle-singularity cusps.
|What is your topic?||Hadronic decays|