Using the Crystal Ball detector at the DORIS II e+e- storage ring, we measure the ηπ0π0 mass spectrum in the reaction e+e-→e+e-ηπ 0π0→e+e-6γ from the ηπ0π0 threshold to about 2500 MeV/c2. The spectrum is dominated by the η′, for which we determine Γγγ(η′)BR(η'→6γ)=0 .36±0.02±0.03 keV. In addition, we observe an enhancement in the cross section near 1900 MeV/c2 which we attribute to the two-photon production of a new resonance X(1900). The angular distributions and the invariant mass distribution of the ηπ0 subsystem are consistent with those expected for the hypothetical η2 meson with JPC=2-+. For this JP assignment the resonance parameters are M(X) = 1876 ±35±50 MeV/c2, Γtot(X)=228±90±34 MeV/c2 and Γγγ(X)BR(X→ηππ) = 0.9±0.2±0.3 keV.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics