Study of (p)over-bar-p→ηπ0π0π0 at rest

Crystal Barrel data are presented on <(p)over bar p> --> eta pi(0) pi(0) pi(0) at rest in liquid hydrogen and also in gaseous hydrogen at 12 bar. Annihilation from the initial P-3(0) state relative to P-3(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 eta(1440). Liquid data determine its mass as M = 1413 MeV, Gamma = 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 eta(1440) decays dominantly to eta sigma. BR[a(0)(98O)pi, a(0) --> eta pi]/BR[eta sigma] = 0.4 +/- 0.2. However, there is strong destructive interference between these two decay modes. There is also a strong, broad eta pi pi component with J(PC) = 0(-+), consistent with an earlier analysis proposing a very wide eta(1800) resonance; it contributes 31% of the eta pi(0) pi(0) pi(0) branching ratio in liquid, At the highest eta pi pi masses, there are definite 2(-+) and 1(++) 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)pi. (C) 1998 Elsevier Science B.V.