Impure Thoughts on Inelastic Dark Matter

TL;DR

This paper explores inelastic dark matter models, highlighting the role of thallium nuclei in DAMA and identifying parameter regions consistent with experimental results, with implications for future detection experiments.

Contribution

It introduces the significance of thallium in inelastic dark matter scattering and delineates parameter space compatible with multiple experiments.

Findings

Thallium nuclei can dominate DAMA scattering at large energy splittings.

A specific delta-m parameter space aligns with all current experimental constraints.

Detection prospects depend on the WIMP velocity distribution tail.

Abstract

The inelastic dark matter scenario was proposed to reconcile the DAMA annual modulation with null results from other experiments. In this scenario, WIMPs scatter into an excited state, split from the ground state by an energy delta comparable to the available kinetic energy of a Galactic WIMP. We note that for large splittings delta, the dominant scattering at DAMA can occur off of thallium nuclei, with A~205, which are present as a dopant at the 10^-3 level in NaI(Tl) crystals. For a WIMP mass m~100GeV and delta~200keV, we find a region in delta-m-parameter space which is consistent with all experiments. These parameters in particular can be probed in experiments with thallium in their targets, such as KIMS, but are inaccessible to lighter target experiments. Depending on the tail of the WIMP velocity distribution, a highly modulated signal may or may not appear at CRESST-II.