Search for the inelastic scattering of dark matter massive particles on the Hf isomer

Abstract The results of the new experimental search for dark matter using the isomer are presented. The γ -rays that are not emitted during the spontaneous decay of this isomer but might arise from the population of excited nuclear levels in 178 Hf due to the inelastic scattering with dark matter massive particles are analyzed in detail. The limits on the half-life of the dark-matter–induced transitions, obtained from limits on these γ -ray intensities, have been improved by about 55 times, from 1.79 × 10 5 y to 10 5 y. Further progress of such experimental efforts is discussed.