Exothermic Double-Disk Dark Matter

TL;DR

This paper explores a novel dark matter model called Exothermic Double-Disk Dark Matter (ExoDDDM), which can explain experimental excesses and offers distinctive detection signatures, combining theoretical modeling with analysis of current and future detection prospects.

Contribution

It introduces a new exothermic dark matter model within the double-disk dark matter framework, explaining experimental excesses and predicting unique detection signatures.

Findings

ExoDDDM can explain the CDMS-Si excess within existing experimental limits.

Light dark matter particles (5-15 GeV) are favored in this model.

Distinctive detection signatures include peaked recoil spectra and reduced annual modulation.

Abstract

If a subdominant component of dark matter (DM) interacts via long-range dark force carriers it may cool and collapse to form complex structures within the Milky Way galaxy, such as a rotating dark disk. This scenario was proposed recently and termed "Double-Disk Dark Matter" (DDDM). In this paper we consider the possibility that DDDM remains in a cosmologically long-lived excited state and can scatter exothermically on nuclei (ExoDDDM). We investigate the current status of ExoDDDM direct detection and find that ExoDDDM can readily explain the recently announced ~3 sigma excess observed at CDMS-Si, with almost all of the 90% best-fit parameter space in complete consistency with limits from other experiments, including XENON10 and XENON100. In the absence of isospin-dependent couplings, this consistency requires light DM with mass typically in the 5-15 GeV range. The hypothesis of ExoDDDM can be tested in direct detection experiments through its peaked recoil spectra, reduced annual modulation amplitude, and, in some cases, its novel time-dependence. We also discuss future direct detection prospects and additional indirect constraints from colliders and solar capture of ExoDDDM. As theoretical proof-of-principle, we combine the features of exothermic DM models and DDDM models to construct a complete model of ExoDDDM, exhibiting all the required properties.