Explaining the DAMA Signal with WIMPless Dark Matter

Abstract

WIMPless dark matter provides a framework in which dark matter particles with a wide range of masses naturally have the correct thermal relic density. We show that WIMPless dark matter with mass around 2-10 GeV can explain the annual modulation observed by the DAMA experiment without violating the constraints of other dark matter searches. This explanation implies distinctive and promising signals for other direct detection experiments, GLAST, and the LHC.

Figures (2)

• Figure 1: Direct detection cross sections for spin-independent $X$-nucleon scattering as a function of dark matter mass $m_X$. The solid curves are the predictions for WIMPless dark matter with connector mass $m_Y = 400~\text{GeV}$ and the Yukawa couplings $\lambda_b$ indicated. The light yellow shaded region is excluded by the experimental results indicated (see text). The dark blue shaded region is consistent with the DAMA signal at $3\sigma$, using 2-4 and 6-14 keVee bins; it may be extended to the medium green shaded region with the inclusion of dark matter streams and 2-6 and 6-14 keVee bins Gondolo:2005hh. The medium-dark magenta shaded region is DAMA-favored when channeling is included (but streams are not) Petriello:2008jj. The cross-hatched region is the conventional DAMA-favored region Belli:1999nz, which is now excluded by other experiments.
• Figure 2: Predicted $\gamma$-ray spectrum for a WIMPless model that explains DAMA with $m_X = 6~\text{GeV}$ and $\sigma_{b \bar{b}} v = 6 \times 10^{-26}~\text{cm}^3~\text{s}^{-1}$ and an NFW halo profile (see text). The data are EGRET's $\gamma$-ray spectrum from the Galactic center Hunter1997.