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Probing light WIMPs with directional detection experiments
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Morgan, B. (Ben) and Green, Anne M. (2012) Probing light WIMPs with directional detection experiments. Physical Review D (Particles, Fields, Gravitation and Cosmology), Volume 86 (Number 8). Article number 083544 . doi:10.1103/PhysRevD.86.083544 ISSN 1550-7998.
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Official URL: http://dx.doi.org/10.1103/PhysRevD.86.083544
Abstract
The CoGeNT and CRESST WIMP direct detection experiments have recently observed excesses of nuclear recoil events, while the DAMA/LIBRA experiment has a long-standing annual modulation signal. It has been suggested that these excesses may be due to light masses of mχ∼5–10 GeV, weakly interacting massive particles (WIMPs). The Earth’s motion with respect to the Galactic rest frame leads to a directional dependence in the WIMP scattering rate, providing a powerful signal of the Galactic origin of any recoil excess. We investigate whether direct detection experiments with directional sensitivity have the potential to observe this anisotropic scattering rate with the elastically scattering light WIMPs proposed to explain the observed excesses. We find that the number of recoils required to detect an anisotropic signal from light WIMPs at 5σ significance varies from 7 to more than 190 over the set of target nuclei and energy thresholds expected for directional detectors. Smaller numbers arise from configurations where the detector is only sensitive to recoils from the highest-speed, and hence most anisotropic, WIMPs. However, the event rate above the threshold is very small in these cases, leading to the need for large experimental exposures to accumulate even a small number of events. To account for this sensitivity to the tail of the WIMP velocity distribution, whose shape is not well known, we consider two exemplar halo models spanning the range of possibilities. We also note that for an accurate calculation, the Earth’s orbital speed must be averaged over. We find that the exposures required to detect 10 GeV WIMPs at a WIMP-proton cross section of 10-4 pb are of order 103 kg day for a 20 keV energy threshold, within reach of planned directional detectors. Lower WIMP masses require higher exposures and/or lower energy thresholds for detection.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Journal or Publication Title: | Physical Review D (Particles, Fields, Gravitation and Cosmology) | ||||
Publisher: | American Physical Society | ||||
ISSN: | 1550-7998 | ||||
Official Date: | 2012 | ||||
Dates: |
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Volume: | Volume 86 | ||||
Number: | Number 8 | ||||
Page Range: | Article number 083544 | ||||
DOI: | 10.1103/PhysRevD.86.083544 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published |
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