Measurement of the slope parameter α for the η→3π0 decay with the Crystal Ball detector at the Mainz Microtron (MAMI-C)03/01/2009
The dynamics of the η→3π0 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 3×106 γp→ηp→3π0p→6γp events yields the value α=−0.032±0.003 for the η→3π0 slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The π0π0invariant-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.