Measurement of the η→3π0 Dalitz plot distribution with the WASA detector at COSY

In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pions was studied using 1.2×105 fully reconstructed events, and the quadratic slope parameter α was determined to be −0.027±0.008(stat)±0.005(syst). The result is consistent with previous measurements and further corroborates the importance of pion-pion final state interactions.