Compatibility of DAMA/LIBRA dark matter detection with other searches

TL;DR

This paper evaluates DAMA/LIBRA dark matter signals against other experimental results, finding some low-mass WIMP parameter regions compatible with all data, especially when considering channeling and certain interaction types.

Contribution

It provides a comprehensive statistical analysis of DAMA/LIBRA data in light of null results, identifying viable low-mass WIMP parameter regions for both spin-independent and spin-dependent interactions.

Findings

Low-mass (~8 GeV) WIMPs can fit DAMA data and other constraints with channeling.

Spin-independent WIMP regions are largely excluded at 3σ, but some low-mass solutions remain.

Certain spin-dependent couplings, especially proton-only, are compatible with all experiments when including indirect detection constraints.

Abstract

The DAMA/NaI and DAMA/LIBRA annual modulation data, which may be interpreted as a signal for the existence of weakly interacting dark matter (WIMPs) in our galactic halo, are examined in light of null results from other experiments. We use the energy spectrum of the combined DAMA modulation data given in 36 bins, and include the effect of channeling. Several statistical tools are implemented in our study: likelihood ratio with a global fit and with raster scans in the WIMP mass and goodness-of-fit (g.o.f.). These approaches allow us to differentiate between the preferred (global best fit) and allowed (g.o.f.) parameter regions. It is hard to find WIMP masses and couplings consistent with all existing data sets. For spin-independent (SI) interactions, the best fit DAMA regions are ruled out to the 3$\sigma$ C.L., even with channeling taken into account. However, for WIMP masses of ~8 GeV some parameters outside these regions still yield a moderately reasonable fit to the DAMA data and are compatible with all 90% C.L. upper limits from negative searches, when channeling is included. For spin-dependent (SD) interactions with proton-only couplings, a range of masses below 10 GeV is compatible with DAMA and other experiments, with and without channeling, when SuperK indirect detection constraints are included; without the SuperK constraints, masses as high as ~20 GeV are compatible. For SD neutron-only couplings we find no parameters compatible with all the experiments. Mixed SD couplings are examined: e.g. ~8 GeV mass WIMPs with a_n = +/- a_p are found to be consistent with all experiments. In short, there are surviving regions at low mass for both SI and SD interactions; if indirect detection limits are relaxed, some SD proton-only couplings at high masses also survive.