QUANTUM EFFECTS ON HIGGS-BOSON PRODUCTION AND DECAY DUE TO MAJORANA NEUTRINOS

We analyze the phenomenological implications for new electroweak physi cs in the Higgs sector in the framework of SU(2)L x U(1)Y theories tha t naturally predict heavy Majorana neutrinos. We calculate the one-loo p Majorana-neutrino contributions to the decay rates of the Higgs boso n into pairs of quarks and intermediate bosons and to its production c ross section via bremsstrahlung in e+e- collisions. It turns out that these are extremely small in three-generation models. On the other han d, the sizeable quantum corrections generated by a conventional fourth generation with a Dirac neutrino may be screened considerably in the presence of a Majorana degree of freedom.