Abstract
Although we have yet to determine whether the DAMA data represents a true discovery of new physics, among such interpretations inelastic dark matter (IDM) can match the energy spectrum of DAMA very well while not contradicting the results of other direct detection searches. In this paper we investigate the general properties that a viable IDM candidate must have and search for simple models that realize these properties in natural ways. We begin by determining the regions of IDM parameter space that are allowed by direct detection searches including DAMA, paying special attention to larger IDM masses. We observe that an inelastic dark matter candidate with electroweak interactions can naturally satisfy observational constraints while simultaneously yielding the correct thermal relic abundance. We comment on several other proposed dark matter explanations for the DAMA signal and demonstrate that one of the proposed alternatives -- elastic scattering of dark matter off electrons -- is strongly disfavored when the modulated and unmodulated DAMA spectral data are taken into account. We then outline the general essential features of IDM models in which inelastic scattering off nuclei is mediated by the exchange of a massive gauge boson, and construct natural models in the context of a warped extra dimension and supersymmetry.
Highlights
The DAMA/NaI and DAMA/LIBRA experiments observe an annual modulation signal in their NaI-based scintillation detectors with a statistical significance of 8.3 σ [1]
4.2 Models Mediated by an Exotic Z′ Gauge Boson In Section 3 we showed that the DAMA signal can arise from the scattering of inelastic dark matter (IDM) off iodine nuclei mediated by an exotic U(1)x gauge boson
In this paper we have considered the possibility that DAMA is a true discovery of dark matter, and investigated the properties a theory of dark matter needs to have in order to account for the data
Summary
The DAMA/NaI and DAMA/LIBRA experiments observe an annual modulation signal in their NaI-based scintillation detectors with a statistical significance of 8.3 σ [1]. An elegant possibility that can account for the signal observed by the DAMA experiments that is consistent with other direct detection experiments is dark matter that scatters inelastically off nuclei [11, 12, 13, 14]. In the inelastic dark matter (IDM) scenario, the dark matter particle χ1 scatters preferentially off target nuclei into a slightly heavier χ2 state The kinematics of this process can enhance the nuclear recoil signal at DAMA relative to other experiments such as CDMS in a couple of ways. When the second term in this expression dominates, the minimal velocity needed to produce a recoil energy ER is lower for heavier nuclei This leads to an enhanced signal at DAMA, which contains iodine with A ≃ 127 as a detector material, relative to CDMS, consisting of germanium with A ≃ 73 [11].
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