New effects observed in central production by the WA102 experiment at   the CERN Omega Spectrometer
  A study of central meson production as a function of the difference in transverse momentum (dPT) of the exchanged particles shows that undisputed qqbar mesons are suppressed at small dPT whereas the glueball candidates are enhanced. In addition, the production cross section for different resonances depends strongly on the azimuthal angle between the two outgoing protons. 
A. Kirk and the WA102 Collaboration