  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 1.2e5 fully reconstructed events, and the quadratic slope parameter alpha
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.
