Partial wave analysis of the ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ and ${\pi }^{-}{\pi }^0{\pi }^0$ systems and the search for a $J^{PC}=1^{-+}$ meson

A partial wave analysis (PWA) of the ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ and ${\pi }^{-}{\pi }^0{\pi }^0$ systems produced in the reaction ${\pi }^{-}p\to (3\pi {)}^{-}p$ at $18\mathrm{GeV}/c$ was carried out using an isobar model assumption. This analysis is based on 3.0 M ${\pi }^{-}{\pi }^0{\pi }^0$ events and 2.6 M ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ events and shows production of the $a_1(1260)$, $a_2(1320)$, ${\pi }_2(1670)$, and $a_4(2040)$ resonances. Results of detailed studies of the stability of partial wave fits are presented. An earlier analysis of 250 K ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ events from the same experiment showed possible evidence for a $J^{PC}=1^{-+}$ exotic meson with a mass of $\sim 1.6\mathrm{GeV}/c^2$ decaying into $\rho \pi$. In this analysis of a higher statistics sample of the $(3\pi {)}^{-}$ system in two charged modes we find no evidence of an exotic meson.