Eur. Phys. J. C (2018) 78: 187
https://doi.org/10.1140/epjc/s10052-018-5653-z

Regular Article - Experimental Physics

Direct detection of MeV-scale dark matter utilizing germanium internal amplification for the charge created by the ionization of impurities

¹ Department of Physics, The University of South Dakota, Vermillion, SD, 57069, USA
² School of Physics and Optoelectronic, Yangtze University, Jingzhou, 434023, China

^* e-mail: Dongming.Mei@usd.edu

Received: 23 October 2017
Accepted: 15 February 2018
Published online: 6 March 2018

Abstract

Light, MeV-scale dark matter (DM) is an exciting DM candidate that is undetectable by current experiments. A germanium (Ge) detector utilizing internal charge amplification for the charge carriers created by the ionization of impurities is a promising new technology with experimental sensitivity for detecting MeV-scale DM. We analyze the physics mechanisms of the signal formation, charge creation, charge internal amplification, and the projected sensitivity for directly detecting MeV-scale DM particles. We present a design for a novel Ge detector at helium temperature ( 4 K) enabling ionization of impurities from DM impacts. With large localized E-fields, the ionized excitations can be accelerated to kinetic energies larger than the Ge bandgap at which point they can create additional electron–hole pairs, producing intrinsic amplification to achieve an ultra-low energy threshold of  0.1 eV for detecting low-mass DM particles in the MeV scale. Correspondingly, such a Ge detector with 1 kg-year exposure will have high sensitivity to a DM-nucleon cross section of  5  10 cm at a DM mass of  10 MeV/c and a DM-electron cross section of  5  10 cm at a DM mass of  1 MeV/c.