Detecting the Milky Way's Dark Disk

TL;DR

This paper investigates the properties and detection implications of the Milky Way's dark disk, showing it enhances detection rates and alters modulation signals for dark matter WIMPs, thus impacting experimental constraints.

Contribution

It introduces the concept of the dark disk's influence on dark matter detection, quantifies its effects on detection rates and modulation signals, and discusses how future surveys can refine WIMP property constraints.

Findings

Dark disk increases detection rates for WIMPs with masses >50 GeV/c^2.

Dark disk boosts annual modulation signals and shifts their phase.

Including dark disk effects tightens constraints on WIMP interaction cross sections.

Abstract

In LambdaCDM, massive satellites are dragged into the disk-plane by dynamical friction where they dissolve into a stellar thick disk and a more massive dark matter disk. The distinctive kinematics of the dark disk matches the stars that also entered in the satellites. The lower velocities of the dark disk with respect to the Earth enhances detection rates at low recoil energy. For WIMP masses > 50 GeV/c^2, the detection rate increases by up to a factor of 3 in the 5 - 20 keV recoil energy range. Comparing this with rates at higher energy will improve constraints on the WIMP mass, particularly for masses > 100 GeV/c^2. The annual modulation signal of the dark disk is significantly boosted and its modulation phase is shifted by ~3 weeks relative to the dark halo. The variation of the observed phase with recoil energy can also be used to determine the WIMP mass once the dark disk properties are fixed by future astronomical surveys. The constraints on the WIMP interaction cross section from current experiments improve by factors of 1.4 to 3.5 when a typical contribution from the dark disk is included.