New Contribution to Neutrinoless Double Beta Decay in Gauge Models

It is pointed out that in a general class of gauge models, there exist new contributions to neutrinoless double $\beta$ transitions, that do not involve a Majorana neutrino but the decay of a doubly charged Higgs boson to electrons. Explicit calculations for the case ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$→${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$ indicate that for reasonable choice of parameters, this new contribution may dominate over that involving light or heavy Majorana neutrinos.