Measurement of the Slope Parameter $\hat{I}\pm$ for the $\hat{I}\cdot \to 3\ddot{I}{€}^0$ decay with the Crystal Ball detector at the Mainz Microtron (MAMI-C)

Abstract

The dynamics of the $\hat{I}\cdot \to 3\ddot{I}{€}^0$ decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for $\hat{I}\cdot$-meson production. The analysis of $3\times 10^6$ ${\hat{I}}^{3}p\to \hat{I}\cdot p\to 3\ddot{I}{€}^{0}p\to 6{\hat{I}}^{3}p$ events yields the value $\hat{I}\pm =-0.032\pm 0.003$ for the $\hat{I}\cdot \to 3\ddot{I}{€}^0$ slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The $\ddot{I}{€}^0\ddot{I}{€}^0$ invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ threshold. The observed effect is small and does not affect our measured value for the slope parameter.