Confirmation of a pi_1^0 Exotic Meson in the ηπ^0 System

Abstract

The exclusive reaction $\ddot{I}{€}^{-}p\to \hat{I}\cdot \ddot{I}{€}^{0}n$, $\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ at 18 GeV$/c$ has been studied with a partial wave analysis on a sample of 23~492 $\hat{I}\cdot \ddot{I}{€}^{0}n$ events from BNL experiment E852. A mass-dependent fit is consistent with a resonant hypothesis for the $P_{+}$ wave, thus providing evidence for a neutral exotic meson with $J^{PC}=1^{-+}$, a mass of $1257\pm 20\pm 25$ MeV$/c^2$, and a width of $354\pm 64\pm 60$ MeV$/c^2$. New interpretations of the meson exotics in neutral $\hat{I}\cdot \ddot{I}{€}^0$ system observed in E852 and Crystal Barrel experiments are discussed.

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