Signature of relic heavy stable neutrinos in underground experiments

Considering heavy stable neutrinos of the 4th generation, we calculate the relic density of such neutrinos in the Universe. Taking into account the condensation of heavy neutrinos in the Galaxy and applying the results of calculations to experimental data from underground experiments on search for WIMPs in elastic neutral current scattering on nuclei, we find an exclusion region of neutrino mass 60 GeV< m < 290 GeV. The bounds obtained from the present underground experiments, while confirming the previous bounds derived from analysis of cosmic ray spectra, are more reliable. We also discuss the first indication of elastic scattering induced by WIMPs in the DAMA experiment, finding a very narrow window of neutrino mass 45 GeV< m <50 GeV compatible with the possible signal rate in the detector.