Weakly Interacting Massive Particles (WIMPs) may constitute a large fraction of the matter in the Universe. The search started with a four seminal papers. Then the influence of annual modulation effect, diurnal modulation effect and subsequently direction sensitive AME was documented. Now, about 30 years later, there are intriguing results from DAMA/LIBRA, CoGeNT, CRESST-II, and recently CDMS-Si, which suggest that there is something with MDM < 10 GeV/c2. However, CDMS-Ge and l. Xenon detectors suggest that there is no DM candidates with MDM> 7. 0 and 12.5 GeV/c2, respectively.
The DAMA/LIBRA has seen WIMP-like events for the last decade. Recent analysis has confirmed the annual modulation effect in all 24 active detectors. The analysis of recent events from cryogenic bolometers (CRESST and CDMS-Si) and CoGeNT suggests that there may be particles with low mass and relatively high velocity, say V = 400-500 km/sec. For MDM = O(5 GeV/c2), the ”exclusion plots” from CDMS-Ge and especially liquid Xenon, depends on particles with velocity close to or beyond the ”escape velocity”. For these low mass particles scattering on high mass nuclei, current methods for background rejection becomes very difficult, some would say disputable. The ability to detect direction of recoil nuclei will considerably facilitate detection of DM candidates using annual modulation effect” (AME) (see DAMA results) and by means of “diurnal modulation effect” (DME). Detection of direction specific annual modulation effect (DS-AME) is especially important in the case of low mass DM candidates Recently, we reviewed status of direct searches for DM candidates, with focus on low mass DM-candidates (MDM < O(5 GeV/c2)).
Until recently, the DM candidates were assumed to be WIMPs “predictable” from SUSY and their mass was assumed to be 30 GeV/c2 < MDM < 300 GeV/c2. Combination of current experimental results and “aftershocks” of recent LHC results lead to increased interest in DM-candidates with smaller mass MDM = O(5 GeV/c2). There exist good candidates in so called Asymmetric Dark Matter Theories (ADMT). Obviously, the particles predicted by ADMT are also weakly interacting and massive. However, we believe that it make sense to keep the two classes separate, i.e. we propose to reserve the name WIMP for the DM-candidates predicted by SUSY.
We argued that particles with MDM = O(5 GeV/c2) can be detected by current generation of detectors but that these detectors are far from being optimal or even reliable because they can not detect DM-candidates with velocity below the Vpeak. There are severe challenges concerning the detectors energy threshold, expected count rate and the rejection of backgrounds. This paper focus on the new class of nano-explosives based DM detectors. In this detectors, the local heating of the nano-size explosives ignites explosion which release the chemical energy stored in such a grain. This energy is about 500-fold larger than energy initially deposed by DM candidate. This leads to effects, e.g. sonic boom, which can be detected remotly. This new class of detectors may be especially important in detection of DM candidates with very low (MDM =O(5 GeV/c2) and very high (MDM > 200 GeV/c2) mass.
C't: Jan Conrad
