DAMA and WIMP dark matter

TL;DR

This paper investigates whether low-mass WIMPs can explain DAMA's annual modulation signal without conflicting with other experiments, highlighting the importance of the channeling effect and suggesting future low-threshold detectors can test this parameter space.

Contribution

It identifies a viable parameter space for elastic WIMPs that explains DAMA results while remaining consistent with null experiments, emphasizing the role of channeling effects.

Findings

A region of WIMP mass 3-8 GeV fits DAMA and null results.

Channeling effect is crucial for the DAMA allowed region.

Inelastic scattering does not reconcile DAMA with other experiments.

Abstract

We study whether spin-independent scattering of weakly-interacting massive particles (WIMPs) with nuclei can account for the annual modulation signal reported by DAMA. We consider both elastic and inelastic scattering processes. We find that there is a region of WIMP parameter space which can simultaneously accommodate DAMA and the null results of CDMS, CRESST, and XENON. This region corresponds to an ordinary, elastically-scattering WIMP with a standard Maxwell-Boltzmann distribution, a mass 3 GeV < m_{DM} <8 GeV, and a spin-independent cross section with nucleons 3 \times 10^{-41} cm^2 < \sigma_p^{SI} < 5 \times 10^{-39} cm^2. This new region of parameter space depends crucially on the recently discovered effect of channeling on the energy threshold for WIMP detection in the DAMA experiment; without the inclusion of this effect, the DAMA allowed region is essentially closed by null experiments. Such low-mass WIMPs arise in many theories of Beyond the Standard Model physics, from minimal extensions of the MSSM to solutions of the baryon-dark matter coincidence problem. We find that inelastic scattering channels do not open up a significant parameter region consistent with all experimental results. Future experiments with low energy thresholds for detecting nuclear recoils, such as CDMSII-Si and those utilizing ultra-low energy germanium detectors, will be able to probe the DAMA region of parameter space.