STUDY OF THE ETA-PI+PI- SYSTEM CENTRALLY PRODUCED IN THE REACTION PP-]PF(ETA-PI+PI-)PS AT 300 GEV/C

The reaction pp --> p(f)(eta-pi+ pi-)p(s) where the eta-pi+ pi- system is centrally produced has been studied at 300 GeV/c incident momentum at the CERN OMEGA spectrometer. The eta-pi +/- mass spectrum shows a strong delta/a0(980) signal having a mass of 984 +/- 4 and GAMMA = 95 +/- 14 MeV. The eta-pi+ pi- mass spectrum shows eta' and f1(1285) signals over little background. A spin-parity analysis of the eta-pi+ pi- system shows evidence for a J(PC) = 1++ peak at the f1(1285) mass but no evidence for the pseudoscalar states eta(1270) and l/eta(1440). No evidence is found for the eta-pi-pi decay of the E/f1(1420) meson for which we set an upper limit BR(E/f1(1420) --> eta-pi-pi) < 0.1 at 95% cl.