Study of p−p → ηπ0π0π0 at rest

Abstract Crystal Barrel data are presented on p − p → ηπ 0 π 0 π 0 at rest in liquid hydrogen and also in gaseous hydrogen at 12 bar. Annihilation from the initial 3 P 0 state relative to 3 P 2 is stronger in liquid than in gas by a factor 2.46 ± 0.15, in fair agreement with a prediction by Batty. There is a definite peak due to η(1440). Liquid data determine its mass as M = 1413 MeV, Γ = 49 ± 8 MeV. The mass is, however, lower in gas than in liquid by 12 ± 3 MeV; we attribute this mass shift to interference with broad background amplitudes. The η (1440) decays dominantly to ησ: BR [ a 0 (980) π , a 0 → ηπ ]/BR[ ησ ] = 0.4 ± 0.2. However, there is strong destructive interference between these two decay modes. There is also a strong, broad ηππ component with J PC = 0 −+ , consistent with an earlier analysis proposing a very wide η(1800) resonance; it contributes 31% of the ηπ 0 π 0 π 0 branching ratio in liquid. At the highest ηππ masses, there are definite 2 −+ and l ++ signals, but we cannot establish precise resonance masses or widths. There is also evidence for the production of f 2 (1565), decaying to a 2 (1320) π .