Evidence for the reaction πp → etaetan at 40 GeV/c

An experiment investigating the reaction π-+p → mγ + n has been performed at the 70 GeV IHEP-accelerator. The final state gammas are measured in a hodoscope spectrometer running on-line with a computer. In a preliminary study of data events of the reaction π-p → etaetan (eta → 2γ) are observed. At invariant masses of the etaeta-system above 1600 MeV up to 2800 MeV a clean sample free of background from π0π0-events is obtained. The ratio of production cross sections of etaeta and π0π0 final states of the order 1:5 which has been found is in agreement with predictions of the quark model. Etaeta angular distributions in the Gottfried-Jackson frame for masses above 1600 MeV are not isotopic