On gluon masses, colour symmetry, and a possible massive ninth gluon
  Gluons acquire a determinate mass from quark loop radiative corrrections and self-interaction, when these are recomputed with the symmetrical theory of generalised functions. The colour symmetry may be~$U(3)$ instead of~$SU(3)$. The symmetry breaks spontaneously and the ninth colour~$SU(3)$ singlet gluon acquires a very large mass. There may be some experimental support for its existence. 
J. J. Lodder