Inelastic Dark Matter, Non-Standard Halos and the DAMA/LIBRA Results

TL;DR

This paper examines how different galactic dark matter velocity models affect the interpretation of DAMA/LIBRA's annual modulation signal, suggesting inelastic dark matter could reconcile DAMA with other experiments under certain conditions.

Contribution

It investigates the impact of non-standard dark matter velocity distributions on direct detection results, highlighting the importance of astrophysical assumptions in interpreting experimental data.

Findings

Via Lactea simulations allow DAMA to be consistent with other experiments for inelastic DM.

Dark Disc model does not improve the compatibility of DAMA results.

Higher mass inelastic dark matter particles are favored under certain velocity distributions.

Abstract

The DAMA collaboration have claimed to detect particle dark matter (DM) via an annual modulation in their observed recoil event rate. This appears to be in strong disagreement with the null results of other experiments if interpreted in terms of elastic DM scattering, while agreement for a small region of parameter space is possible for inelastic DM (iDM) due to the altered kinematics of the collision. To date most analyses assume a simple galactic halo DM velocity distribution, the Standard Halo Model, but direct experimental support for the SHM is severely lacking and theoretical studies indicate possible significant differences. We investigate the dependence of DAMA and the other direct detection experiments on the local DM velocity distribution, utilizing the results of the Via Lactea and Dark Disc numerical simulations. We also investigate effects of varying the solar circular velocity, the DM escape velocity, and the DAMA quenching factor within experimental limits. Our data set includes the latest ZEPLIN-III results, as well as full publicly available data sets. Due to the more sensitive dependence of the inelastic cross section on the velocity distribution, we find that with Via Lactea the DAMA results can be consistent with all other experiments over an enlarged region of iDM parameter space, with higher mass particles being preferred, while Dark Disc does not lead to an improvement. A definitive test of DAMA for iDM requires heavy element detectors.