LIMITS ON HEAVY WIMP MASSES AND INTERACTIONS

We consider generic heavy WIMPs with effective neutral current coupling constant g'. We show that cosmology, experiments and unitarity considerations limit their masses from above as well as from below. There are also absolute lower limits of 4 x 10(-5)g and 6 x 10(-5)g for the couplings of Dirac and Majorana neutrinos, respectively. In the experimentally interesting region m(N) congruent-to O(100) GeV we find a stringent bound g' greater-than-or-similar-to 0.1g. In U (1)' models cosmology implies an upper limit of about 1 TeV on the Z' and on the WIMP masses, but only in the absence of ZZ' mixing.