Search for low-mass WIMPs with EDELWEISS-II heat-and-ionization detectors

Abstract

We report on a search for low-energy (E < 20 keV) WIMP-induced nuclear recoils using data collected in 2009 − 2010 by EDELWEISS from four germanium detectors equipped with thermal sensors and an electrode design (ID) which allows to efficiently reject several sources of background. The data indicate no evidence for an exponential distribution of low-energy nuclear recoils that could be attributed to WIMP elastic scattering after an exposure of 113 kg·d. For WIMPs of mass 10 GeV, the observation of one event in the WIMP search region results in a 90% CL limit of 1.0 × 10 −5 pb on the spin-independent WIMP-nucleon scattering cross-section, which constrains the parameter space associated with the findings reported by the CoGeNT, DAMA and CRESST experiments.

Search for Low-Mass Weakly Interacting Massive Particles with SuperCDMS

“…The 90% C.L. exclusion limits shown are CDMS II Ge [22] (dotted dark red), CDMS II Ge low threshold [17] (dashed-dotted red), CDMSlite [20] (solid dark red, extending to ∼3 GeV=c 2 ), LUX [35] (solid green, extending to ∼5.5 GeV=c 2 ), XENON10 S2 only [19,36] (dashed dark green, extending to ∼4.5 GeV=c 2 ), and EDELWEISS low threshold [18] …”

“…Since light WIMPs produce only low-energy nuclear recoils, experiments optimized for masses ≳30 GeV=c 2 have searched for light WIMPs by lowering their analysis energy thresholds [16][17][18][19]. This additional sensitivity comes with higher background rates because resolution effects degrade particle discrimination at low energies.…”

Galactic searches for dark matter

“…EDELWEISS-II has also presented a low threshold analysis with a goal of improving the sensitivity to WIMPs with mass below 10 GeV (Armengaud et al, 2012). From an exposure of 113 kg-days and the observation of one event in the signal region, at 5 GeV the limit on the cross section is approximately three times weaker than the corresponding limits from CDMS-II.…”

New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment

“…In this case, the number densities of the two are also related, suggesting searches for particles with masses of a few GeV/c 2 . Hints of WIMP signals near detector thresholds [17][18][19][20][21], and an excess of gamma-ray emission from the Galactic Center [22], have also contributed to interest in the low-mass WIMP region [5,[23][24][25][26][27][28][29][30][31][32].…”

“…The improvement in sensitivity over the first CDMSlite run is due to the increase in exposure, the reduction in threshold, and the [23], SuperCDMS low threshold (red thin dashed) [24], EDELWEISS-II (red thin dotted) [25], LUX (dark-yellow thick dashed-dot) [5], CRESST (magenta thick dashed) [27], and DAMIC (purple thick dotted) [28]. Closed regions are CDMS II Si 90 % C.L.…”