A case for colour

A possible explanation of the psi-particles is presented in the context of Han-Nambu colour theory. The strong group is taken to be SU3'XSU3'' and it is proposed that there are vector mesons in the (1,1), (8,1), (1,8) and (8, 8) representations. It is assumed that both SU3 subgroups break to SU2XU1, which implies a fourth psi-particle coupled directly to the photon. A provisional parametrization on the basis of Okubo-type mass formulae suggests a mass for this particle about 4.8GeV/csup(2). The theory also predicts charged coloured vector mesons rhosub(C,D)sup (+-) with the same mass as psi(3.1) and psi(3.7) and coloured mesons Ksub(C,D)sup(*+-0) with masses approximately 3.9GeV/csup(2) and 4.5GeV/csup(2). Coloured pseudoscalar mesons πsub(C,D) have decay properties similar to rhosub (C,D). They do not couple directly to the photon but are accessible from psisub(1.2) by radiative transitions and provide a possible explanation of the new state at 3.5GeV/c sup(2). It is also developed a renormalizable theory of weak and electromagnetic interactions with hadronic currents with the necessary group-theoretic and observed hypercharge-changing properties. These requirements together with ''universality'' are sufficient to determine the theory almost uniquely. Its implications for coloured particles are examined and it is shown that the only long-lived coloured vector meson is Ksub(c)sup(*+) or (rhosub(c)sup(+)) in the alternative version with mean life about 10sup(-13)s