A study of the centrally produced 3pi channel in pp interactions at 450   GeV/c
  The reaction pp -> pf (pi+pi-pi0) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. The analysis confirms the previous observation that all undisputed qqbar states are suppressed at small dPT. In addition, a clear difference is observed in the production mechanism for the eta and omega. 
The WA102 Collaboration, D. Barberis et al