Partial-wave analysis of ${\tau }^{-}\to {\pi }^{-}{\pi }^{-}{\pi }^{+}{\nu }_{\tau }$ at Belle

We present preliminary results of a partial-wave analysis of ${\tau }^{-}\to {\pi }^{-}{\pi }^{-}{\pi }^{+}{\nu }_{\tau }$ in data from the Belle experiment at the KEKB ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ collider. We demonstrate the presence of the ${\mathrm{a}}_1(1420)$ and ${\mathrm{a}}_1(1640)$ resonances in tauon decays and measure their masses and widths. We also present validation of our findings using a model-independent approach. Our results can improve modeling in simulation studies necessary for measuring the tauon electric and magnetic dipole moments and Michel parameters.