High Energy Neutrinos from Dark Matter Decay

Abstract

Discovery of high-energy neutrino events by the IceCube Collaboration \cite{IC1} opened a new era of experimental neutrino astrophysics. The analysis of starting and uncontained cascade and track events based on multiple years of IceCube data \cite{ICRC} leaves no doubt that the excess of the neutrino events above 100 TeV or so cannot be explained by atmospheric neutrinos. Isotropic distribution of these events, showing no significant evidence of spatial or temporal correlations with known sources, points to extragalactic origin of high energy neutrinos. However, the production mechanism of this cosmic component is not clear yet. It might have astrophysical origin being produced by cosmic rays with a typical power law spectrum, or cosmological origin related to dark matter decay which would produce the neutrino spectrum in a form of one ore more bumps. Here we present a model of decaying dark matter represented by heavy mirror neutrinos, with masses of few PeV, from a parallel gauge sector with very large electroweak scale, in which ordinary high energy neutrinos are produced via the majoron portal. In this case the neutrino spectrum would consist of two bumps, one with maximal energy of about 0.5 PeV, and another with maximal energy of about 5 PeV. In addition, the majoron decay produces the neutrino mass eigenstates $\nu_{1,2,3}$ with fractions proportional to the neutrino masses squared, $F_1 : F_2 : F_3 = m_1^2 : m_2^2 : m_3^2$, with specific implications for the flavor composition of the IceCube neutrinos. Thus, precise determination of the energy spectrum and flavor content of the IceCube neutrinos in the future can discriminate between their cosmological and astrophysical origins.