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Bosonic super-WIMPs, including pseudoscalar and vector particles, are dark matter candidates. Until now, many underground experiments searches for super-WIMPs have been performed in the mass range of a few $rm keV/c^2$ to 1 $rm MeV/c^2$. All these searches utilize the absorption process of a super-WIMP by a target atom in the detector, which is similar to the photoelectric effect. In this study, we consider another process, namely, a Compton-like process. As an example, we compare the cross-section of a germanium atom for the absorption process with that of a Compton-like process. Our findings indicate that the cross-section for the Compton-like process becomes dominant, compared to that for the absorption process for mass above approximately 150 $rm keV/c^2$ for both pseudoscalar and vector super-WIMPs. In particular, the cross-section for the Compton-like process for a vector super-WIMP becomes increasingly greater than that for the absorption process by an order of magnitude to two orders of magnitude in the 400 $rm keV/c^2$ to 1 $rm MeV/c^2$ mass range, respectively. By including the Compton-like process, which has not been used in any other super-WIMP search experiment, the experimental upper limits can be improved.
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We present the first search for bosonic super-WIMPs as keV-scale dark matter candidates performed with the GERDA experiment. GERDA is a neutrinoless double-beta decay experiment which operates high-purity germanium detectors enriched in $^{76}$Ge in an ultra-low background environment at the Laboratori Nazionali del Gran Sasso (LNGS) of INFN in Italy. Searches were performed for pseudoscalar and vector particles in the mass region from 60 keV/c$^2$ to 1 MeV/c$^2$. No evidence for a dark matter signal was observed, and the most stringent constraints on the couplings of super-WIMPs with masses above 120 keV/c$^2$ have been set. As an example, at a mass of 150 keV/c$^2$ the most stringent direct limits on the dimensionless couplings of axion-like particles and dark photons to electrons of $g_{ae} < 3 cdot 10^{-12}$ and ${alpha}/{alpha} < 6.5 cdot 10^{-24}$ at 90% credible interval, respectively, were obtained.
The CDMS and EDELWEISS collaborations have combined the results of their direct searches for dark matter using cryogenic germanium detectors. The total data set represents 614 kg.d equivalent exposure. A straightforward method of combination was chosen for its simplicity before data were exchanged between experiments. The results are interpreted in terms of limits on spin-independent WIMP-nucleon cross-section. For a WIMP mass of 90 GeV/c^2, where this analysis is most sensitive, a cross-section of 3.3 x 10^{-44} cm^2 is excluded at 90% CL. At higher WIMP masses, the combination improves the individual limits, by a factor 1.6 above 700 GeV/c^2. Alternative methods of combining the data provide stronger constraints for some ranges of WIMP masses and weaker constraints for others.
We present results of searches for vector and pseudo-scalar bosonic super-WIMPs, which are dark matter candidates with masses at the keV-scale, with the XENON100 experiment. XENON100 is a dual-phase xenon time projection chamber operated at the Laboratori Nazionali del Gran Sasso. A profile likelihood analysis of data with an exposure of 224.6 live days $times$ 34,kg showed no evidence for a signal above the expected background. We thus obtain new and stringent upper limits in the $(8-125)$,keV/c$^2$ mass range, excluding couplings to electrons with coupling constants of $g_{ae} > 3times10^{-13}$ for pseudo-scalar and $alpha/alpha > 2times10^{-28}$ for vector super-WIMPs, respectively. These limits are derived under the assumption that super-WIMPs constitute all of the dark matter in our galaxy.
We present the results of a search for elastic scattering from galactic dark matter in the form of Weakly Interacting Massive Particles (WIMPs) in the 4-30 GeV/$c^2$ mass range. We make use of a 582 kg-day fiducial exposure from an array of 800 g Germanium bolometers equipped with a set of interleaved electrodes with full surface coverage. We searched specifically for $sim 2.5-20$ keV nuclear recoils inside the detector fiducial volume. As an illustration the number of observed events in the search for 5 (resp. 20) GeV/$c^2$ WIMPs are 9 (resp. 4), compared to an expected background of 6.1 (resp. 1.4). A 90% CL limit of $4.3times 10^{-40}$ cm$^2$ (resp. $9.4times 10^{-44}$ cm$^2$) is set on the spin-independent WIMP-nucleon scattering cross-section for 5 (resp. 20) GeV/$c^2$ WIMPs. This result represents a 41-fold improvement with respect to the previous EDELWEISS-II low-mass WIMP search for 7 GeV/$c^2$ WIMPs. The derived constraint is in tension with hints of WIMP signals from some recent experiments, thus confirming results obtained with different detection techniques.
We present the result of an indirect search for high energy neutrinos from WIMP annihilation in the Sun using upward-going muon (upmu) events at Super-Kamiokande. Datasets from SKI-SKIII (3109.6 days) were used for the analysis. We looked for an excess of neutrino signal from the Sun as compared with the expected atmospheric neutrino background in three upmu categories: stopping, non-showering, and showering. No significant excess was observed. The 90% C.L. upper limits of upward-going muon flux induced by WIMPs of 100 GeV/c$^2$ were 6.4$times10^{-15}$ cm$^{-2}$ sec$^{-1}$ and 4.0$times10^{-15}$ cm$^{-2}$ sec$^{-1}$ for the soft and hard annihilation channels, respectively. These limits correspond to upper limits of 4.5$times10^{-39}$ cm$^{-2}$ and 2.7$times10^{-40}$ cm$^{-2}$ for spin-dependent WIMP-nucleon scattering cross sections in the soft and hard annihilation channels, respectively.
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