Gordon Krnjaic - Fermilab - A Dark Matter Interpretation of Excesses in Multiple Direct Detection Experiments
E 188 (BLDG 362)
We present a novel unifying interpretation of excess event rates observed in several dark matter direct-detection experiments that utilize single-electron threshold semiconductor detectors. Despite their different locations, exposures, readout techniques, detector composition, and operating depths, these experiments all observe statistically significant excess event rates of ~10 Hz/kg. However, none of these persistent excesses has yet been reported as a dark matter signal because their common spectral shapes are inconsistent with dark matter particles scattering elastically off detector nuclei or electrons. We show that these results can be reconciled if the semiconductor detectors are seeing a collective inelastic process known as a plasmon. We further show that plasmon excitation could arise in two compelling dark matter scenarios, both of which can explain rates of existing signal excesses in germanium and, at least at the order of magnitude level, across several traditional WIMP searches and single-electron threshold detectors. Both dark matter scenarios motivate a radical rethinking of the standard interpretations of dark matter-electron scattering from recent experiments.