  The non-Abelian nature of QCD suggests that particles that have a gluon
constituent, such as glueballs or hybrids, should exist. Experiments WA76, WA91
and WA102 have performed a dedicated search for these states in central
production using the CERN Omega Spectrometer. Several non-qqbar candidates have
been observed. This paper presents a study of central meson production as a
function of the difference in transverse momentum (dPT) of the exchanged
particles which shows that undisputed qqbar mesons are suppressed at small dPT
whereas the glueball candidates are enhanced.
