Measurement of the invariant-mass spectrum for the two photons from the η→π0γγ decay

New results on the rare, doubly radiative decay eta ->pi(0)gamma gamma have been obtained from a revised analysis of the Crystal Ball experiment performed at the AGS. The analysis yields the first information on the dependence of the decay width, Gamma(eta ->pi(0)gamma gamma), on the two-photon invariant mass squared, m(2)(gamma gamma). A re-evaluation of the branching ratio is also made, BR(eta ->pi(0)gamma gamma)=(2.21 +/- 0.24(stat)+/- 0.47(syst))x10(-4); it implies that the decay width is Gamma(eta ->pi(0)gamma gamma)=0.285 +/- 0.031(stat)+/- 0.061(syst) eV. These results are close to predictions based on chiral perturbation theory with vector-meson dominance.