Abstract
We present the results of the first IceCube search for dark matter annihilation in the center of the Earth. Weakly interacting massive particles (WIMPs), candidates for dark matter, can scatter off nuclei inside the Earth and fall below its escape velocity. Over time the captured WIMPs will be accumulated and may eventually self-annihilate. Among the annihilation products only neutrinos can escape from the center of the Earth. Large-scale neutrino telescopes, such as the cubic kilometer IceCube Neutrino Observatory located at the South Pole, can be used to search for such neutrino fluxes. Data from 327 days of detector livetime during 2011/2012 were analyzed. No excess beyond the expected background from atmospheric neutrinos was detected. The derived upper limits on the annihilation rate of WIMPs in the Earth and the resulting muon flux are an order of magnitude stronger than the limits of the last analysis performed with data from IceCube’s predecessor AMANDA. The limits can be translated in terms of a spin-independent WIMP–nucleon cross section. For a WIMP mass of 50 GeV this analysis results in the most restrictive limits achieved with IceCube data.
Highlights
A large number of observations, like rotation curves of galaxies and the cosmic microwave background temperature anisotropies, suggests the existence of an unknown component of matter [1], commonly referred to as dark matter
We present the results of the first IceCube search for dark matter annihilation in the center of the Earth
Different strategies are pursued to search for these particles: at colliders, dark matter particles could be produced [3], in direct detection experiments, nuclear recoils from a massive target could be observed [4,5,6,7], and indirect detection experiments search for a signal of secondary particles produced by self-annihilating dark matter [8,9,10,11,12]
Summary
A large number of observations, like rotation curves of galaxies and the cosmic microwave background temperature anisotropies, suggests the existence of an unknown component of matter [1], commonly referred to as dark matter. Neutrinos are the only messenger particles that can be used to probe for dark matter in close-by massive baryonic bodies like the Sun or the Earth. The WIMPs may scatter weakly on nuclei in the celestial bodies and lose energy Over time, this leads to an accumulation of dark matter in the center of the bodies. The inner strings at the center of IceCube comprise DeepCore [31], a more densely instrumented sub-array equipped with higher quantum efficiency DOMs. While the large ice overburden above the detector provides a shield against downward going, cosmic ray induced muons with energies 500 GeV at the surface, most analyses focus on upward going neutrinos employing the entire Earth as a filter. The search for WIMP annihilation signatures at the center of the Earth takes advantage of these two background rejection techniques as the expected signal will be vertically up-going and of low energy
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