The Inert Doublet Model and Inelastic Dark Matter

TL;DR

This paper explores elastic and inelastic dark matter scattering within the Inert Doublet Model, showing it can explain DAMA data and match cosmological abundance, with potential for lighter candidates under certain symmetries.

Contribution

It demonstrates the viability of the Inert Doublet Model to account for DAMA signals through both elastic and inelastic scattering scenarios, including natural protection of mass splitting.

Findings

Candidates with 535 GeV to 50 TeV mass can reproduce DAMA data.

Inelastic dark matter candidates can have the correct relic abundance.

Lighter candidates (~50 GeV) are possible with approximate PQ symmetry and dark sector asymmetry.

Abstract

The annual modulation observed by DAMA/NaI and DAMA/Libra may be interpreted in terms of elastic or inelastic scattering of dark matter particles. In this paper we confront these two scenarios within the framework of a very simple extension of the Standard Model, the Inert Doublet Model (IDM). In this model the dark matter candidate is a scalar, the lightest component of an extra Higgs doublet. We first revisit the case for the elastic scattering of a light scalar WIMP, M_DM~10 GeV, a scenario which requires that a fraction of events in DAMA are channelled. Second we consider the possibility of inelastic Dark Matter (iDM). This option is technically natural in the IDM, in the sense that the mass splitting between the lightest and next-to-lightest neutral scalars may be protected by a Peccei-Quinn (PQ) symmetry. We show that candidates with a mass M_DM between ~535 GeV and ~50 TeV may reproduce the DAMA data and have a cosmic abundance in agreement with WMAP. This range may be extended to candidates as light as ~50 GeV if we exploit the possibility that the approximate PQ symmetry is effectively conserved and that a primordial asymmetry in the dark sector may survive until freeze-out.