The Majoron and left-handed neutrino masses in SU(5)

We consider the spontaneous breaking of B?L in SU(5) in connection with left-handed neutrino masses. We show that the ensuing Goldstone boson, “the majoron”, is harmless. The low-energy predictions are the same as in the SU(2)_L × U(1) majoron model which, in particular, predicts the existence of doubly and singly charged scalars, with masses ?250 GeV and with a mass ratio of √2. Going to SU(5), one would expect these scalars to escape to the grand unified mass. This does not happen and, surprisingly, even the ratio √2 is preserved.