LIMITS ON TAU-NEUTRINO AS DARK MATTER

If the tau neutrino is to constitute the cold dark matter of the galactic halo, as has recently been suggested, it should have a mass between a few MeV and 35 MeV, and a magnetic moment around 10(-6) Bohr magnetons. We investigate the consequences of these neutrino properties for some rare decays and other processes. In particular, we find that such a neutrino could be established or ruled out at a tau-charm factory by studying the decay psi(2S) --> J/psi + pi-pi. Neutral-current processes in beam dump experiments are also a sensitive probe of these neutrinos. Measurements of low-energy cosmic ray positions may also constrain this model once solar wind modulation effects are better understood.