A partial wave analysis of the $π^- π^- π^+$ and $π^- π^0 π^0$ systems and the search for a $J^{PC}=1^{-+}$ meson

Abstract

A partial wave analysis (PWA) of the $π^- π^- π^+$ and $π^- π^0 π^0$ systems produced in the reaction $π^- p \to (3π)^-p$ at 18 GeV/$c$ was carried out using an \emph{isobar} model assumption. This analysis is based on 3.0M $π^- π^0 π^0$ events and 2.6M $π^- π^-π^+$ events and shows production of the $a_1(1260)$, $a_2(1320)$, $π_2(1670)$ and $a_4(2040)$ resonances. Results of detailed studies of the stability of partial wave fits are presented. An earlier analysis of 250K $π^- π^- π^+$ events from the same experiment showed possible evidence for a $J^{PC}=1^{-+}$ exotic meson with a mass of $\sim$1.6 GeV/$c^2$ decaying into $ρπ$. In this analysis of a higher statistics sample of the $(3π)^-$ system in two charged modes we find no evidence of an exotic meson.