A model for baryonium

The spectrum of qqanti qanti q hadrons examined in a quark-gluon model yields two types of state both of which have small mesonic widths and may be associated with baryoniums. One type (T-diquonium) has normal hadronic widths into Banti B, while the other (M-diquonium) is narrow and decays into Banti B only reluctantly, preferring if possible to decay by cascade. The experience gained from ordinary hadron spectroscopy, plus some new phenomenological observations, allow one to predict the spectrum and properties of both types in considerable detail. The result bears close resemblance to present experiment. The existence of narrow M-diquonium states following only from hidden colour, and if established would be a major triumph for the concept. It would be, however, only the first example of a quite general phenomenon which may well develop into a whole new branch of hadron spectroscopy. (Auth.)