Magnetic Inelastic Dark Matter: Directional Signals Without a Directional Detector

TL;DR

This paper proposes a novel method to detect directional signals of magnetic inelastic dark matter through delayed coincidence events, enabling directional detection without specialized detectors, and demonstrates its feasibility with current experiments.

Contribution

It introduces a new approach to identify directional dark matter signals via photon emission after inelastic scattering, bypassing the need for directional detectors.

Findings

Directional modulation of WIMP recoil tracks can be observed.

Current experiments can constrain MiDM parameters with modest exposure.

Recoil and photon detection enable reconstruction of dark matter velocity.

Abstract

The magnetic inelastic dark matter (MiDM) model, in which dark matter inelastically scatters off nuclei through a magnetic dipole interaction, has previously been shown to reconcile the DAMA/LIBRA annual modulation signal with null results from other experiments. In this work, we explore the unique directional detection signature of MiDM. After the dark matter scatters into its excited state, it decays with a lifetime of order 1 microsecond and emits a photon with energy ~100 keV. Both the nuclear recoil and the corresponding emitted photon can be detected by studying delayed coincidence events. The recoil track and velocity of the excited state can be reconstructed from the nuclear interaction vertex and the photon decay vertex. The angular distribution of the WIMP recoil tracks is sharply peaked and modulates daily. It is therefore possible to observe the directional modulation of WIMP-nucleon scattering without a large-volume gaseous directional detection experiment. Furthermore, current experiments such as XENON100 can immediately measure this directional modulation and constrain the MiDM parameter space with an exposure of a few thousand kg day.