Differentiating hidden sector dark matter from light WIMPs with Germanium detectors

TL;DR

This paper compares light WIMP and hidden sector dark matter models using Germanium detectors, highlighting their distinct recoil spectra and discussing how upcoming experiments can differentiate between them.

Contribution

It provides a detailed comparison of WIMP and hidden sector dark matter models, emphasizing their spectral differences and potential for experimental discrimination.

Findings

Recoil spectra of the two models approximately agree at certain masses.

Hidden sector dark matter predicts a sharply rising spectrum, unlike WIMPs.

Upcoming experiments can distinguish between the models through precise measurements.

Abstract

Light WIMP dark matter and hidden sector dark matter have been proposed to explain the DAMA, CoGeNT and CRESST-II data. Both of these approaches feature spin independent elastic scattering of dark matter particles on nuclei. Light WIMP dark matter invokes a single particle species which interacts with ordinary matter via contact interactions. By contrast hidden sector dark matter is typically multi-component and is assumed to interact via the exchange of a massless mediator. Such hidden sector dark matter thereby predicts a sharply rising nuclear recoil spectrum, $dR/dE_R \sim 1/E_R^2$ due to this dynamics, while WIMP dark matter predicts a spectrum which depends sensitively on the WIMP mass, $m_\chi$. We compare and contrast these two very different possible origins of the CoGeNT low energy excess. In the relevant energy range, the recoil spectra predicted by these two theories approximately agree provided $m_\chi \simeq 8.5$ GeV - close to the value favoured from fits to the CoGeNT and CDMS low energy data. Forthcoming experiments including C-4, CDEX, and the MAJORANA demonstrator, are expected to provide reasonably precise measurements of the low energy Germanium recoil spectrum, including the annual modulation amplitude, which should differentiate between these two theoretical possibilities.