Study of p−p → ηπ0π0π0 at rest Original Research Article

Crystal Barrel data are presented on p−p → ηπ0π0π0 at rest in liquid hydrogen and also in gaseous hydrogen at 12 bar. Annihilation from the initial 3P0 state relative to 3P2 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 [a0(980)π,a0 → 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 JPC = 0−+, consistent with an earlier analysis proposing a very wide η(1800) resonance; it contributes 31% of the ηπ0π0π0 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 f2 (1565), decaying to a2 (1320)π.