Measurement of the slope parameter $\ensuremath{\alpha}$ for the $\ensuremath{\eta}\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}$ decay with the Crystal Ball detector at the Mainz Microtron (MAMI-C)

Measurement of the slope parameter $α$ for the $η \to 3 π^{0}$ decay with the Crystal Ball detector at the Mainz Microtron (MAMI-C)

S. Prakhov et al. (Crystal Ball Collaboration at MAMI and A2 Collaboration)

Phys. Rev. C 79, 035204 – Published 16 March 2009

Abstract

The dynamics of the $η \to 3 π^{0}$ 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 $η$ -meson production. The analysis of $3 \times 10^{6} γ p \to η p \to 3 π^{0} p \to 6 γ p$ events yields the value $α = - 0.032 \pm 0.003$ for the $η \to 3 π^{0}$ slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The $π^{0} π^{0}$ invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the $π^{+} π^{-}$ threshold. The observed effect is small and does not affect our measured value for the slope parameter.