Heavy neutrinos: The heterodox strikes back

The properties of a fourth generation doublet neutrino are severely constrained by the recent LEP results. This species is no longer a viable candidate for the dark matter which pervades the universe. Those who favour the heterodox will be relieved to notice that neutrinos embedded inside electroweak gauge triplets - a promising if unconventional possibility - may still solve the astronomical missing mass conundrum. High energy physics and cosmological relevance favour such a neutrino to have a mass in the range 30-80 GeV. Whilst elusively absent from the Z0 boson peak width, these new dark matter candidates are associated by gauge symmetry to charged Dirac fermions whose discovery should not escape the LEP detectors once the beam energy reaches ≅ 100 GeV. (orig.)