Nuclear Spin in Direct Dark Matter Search

The Weakly Interacting Massive Particles (WIMPs) are among the main candidates for the relic dark matter (DM). The idea of the direct DM detection relies on elastic in-dependent (SD) and spin-independent (SI) interaction of WIMPs with target nuclei. The importance of the SD WIMP-nucleus interaction for reliable DM detection is argued. The absolute lower bound for the detection rate can naturally be due to SD interaction. An experiment aimed at detecting DM with sensitivity higher than 10^{-5} event/day/kg should have a non-zero-spin target.