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Register a new userDAMA annual modulation effect and asymmetric mirror matter
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The long-standing model-independent annual modulation effect measured by DAMA Collaboration is examined in the context of asymmetric mirror dark matter, assuming that dark atoms interact with target nuclei in the detector via kinetic mixing between mirror and ordinary photons, both being massless. The relevant ranges for the kinetic mixing parameter are obtained taking into account various existing uncertainties in nuclear and particle physics quantities as well as characteristic density and velocity distributions of dark matter in different halo models.
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The DAMA experiment using ultra low background NaI(Tl) crystal scintillators has measured an annual modulation effect in the keV region which satisfies all the peculiarities of an effect induced by Dark Matter particles. In this paper we analyze this annual modulation effect in terms of mirror Dark Matter, an exact duplicate of ordinary matter from parallel hidden sector, which chemical composition is dominated by mirror helium while it can also contain significant fractions of heavier elements as Carbon and Oxygen. Dark mirror atoms are considered to interact with the target nuclei in the detector via Rutherford-like scattering induced by kinetic mixing between mirror and ordinary photons, both being massless. In the present analysis we consider various possible scenarios for the mirror matter chemical composition. For all the scenarios, the relevant ranges for the kinetic mixing parameter have been obtained taking also into account various existing uncertainties in nuclear and particle physics quantities.
The DAMA collaboration reported an annually modulated rate with a phase compatible with a Dark Matter induced signal. We point out that a slowly varying rate can bias or even simulate an annual modulation if data are analyzed in terms of residuals computed by subtracting approximately yearly averages starting from a fixed date, rather than a background continuous in time. In the most extreme case, the amplitude and phase of the annual modulation reported by DAMA could be alternatively interpreted as a decennial growth of the rate. This possibility appears mildly disfavoured by a detailed study of the available data, but cannot be safely excluded. In general, a decreasing or increasing rate could partially reduce or enhance a true annual modulation, respectively. The issue could be clarified by looking at the full time-dependence of the DAMA total rate, not explicitly published so far.
If dark matter is composed of new fundamental particles, Earths orbital motion around the Sun may induce an annual modulation in the rate at which these particles interact in a terrestrial detector. The DAMA collaboration has identified at a 12$sigma$ confidence level such an annual modulation in their event rate. One previously proposed explanation is `plasma dark matter (e.g. mirror dark matter) which would have electron recoils in the detector from interactions via kinetic mixing. We perform a chi-squared goodness of fit test of this plasma dark matter model to DAMA/LIBRA modulation amplitude which rejects the hypothesis of plasma dark matter as an explanation of this data at greater than 7$sigma$.
A claim for evidence of dark matter interactions in the DAMA experiment has been recently reinforced. We employ a new type of germanium detector to conclusively rule out a standard isothermal galactic halo of Weakly Interacting Massive Particles (WIMPs) as the explanation for the annual modulation effect leading to the claim. Bounds are similarly imposed on a suggestion that dark pseudoscalars mightlead to the effect. We describe the sensitivity to light dark matter particles achievable with our device, in particular to Next-to-Minimal Supersymmetric Model candidates.
This paper summarizes in a simple and intuitive way why the neutrons, the muons and the solar neutrinos cannot give any significant contribution to the DAMA annual modulation results. A number of these elements have already been presented in individual papers; they are recalled here. Afterwards, few simple considerations are summarized which already demonstrate the incorrectness of the claim reported in PRL 113 (2014) 081302.
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