Pseudo-Goldstone bosons in the Pati-Salam model

It is shown that there exist 17 (real) 'pseudo'-Goldstone bosons in the Pati-Salam (Phys. Rev.; D10:275 (1974)) model. These are not of the usual type, but are due to making the potential invariant under a much larger symmetry than the gauge group. This leads to the model being non-renormalisable. One of these 'pseudo'-Goldstones would mediate the unobserved K0 → μe decay. This implies a lower bound of about 100 GeV on the mass of this particular pseudo-Goldstone boson and suggests that the complete potential should be minimised, which could lead to a significantly different structure for the symmetry breaking than that deduced by Pati and Salam. Possible ways of overcoming these difficulties are discussed. (author)