Pinning down the cosmic ray source mechanism with new IceCube data

Abstract

Very recently the IceCube Collaboration has reported an observation of 28 neutrino candidates with energies between 50 TeV and 2 PeV, constituting a 4.1$\sigma$ excess compared to the atmospheric background. In this article we investigate the compatibility between the data and a hypothesized unbroken power-law neutrino spectrum for various values of spectral index Γ>= 2. We show that Γ~ 2.3 is consistent at the ~ 1.5$\sigma$ level with the observed events up to 2 PeV and to the null observation of events at higher energies. We then assume that the sources of this unbroken spectrum are Galactic, and deduce (i) an energy-transfer fraction from parent protons to pions, and (ii) a way of discriminating among models which have been put forth to explain the "knee" and "ankle" features of the cosmic ray spectrum. Future IceCube data will test the unbroken power law hypothesis and provide a multi-messenger approach to explaining features of the cosmic ray spectrum, including the transition from Galactic to extragalactic dominance.

Matching version to be published in Physical Review D

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• First combined search for neutrino point-sources in the Southern Hemisphere with the ANTARES and IceCube neutrino telescopes
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• Galactic PeV Neutrinos
• Evidence for a break in the spectrum of astrophysical neutrinos
• Estimating the contribution of Galactic sources to the diffuse neutrino flux
• Constraints to a Galactic Component of the Ice Cube cosmic neutrino flux from ANTARES
• Neutron β-decay as the origin of IceCube's PeV (anti)neutrinos
• Angular correlation of cosmic neutrinos with ultrahigh-energy cosmic rays and implications for their sources
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• Early Decay of Peccei-Quinn Fermion and the IceCube Neutrino Events
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• On the angular distribution of IceCube high-energy events
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• Report from the Multi-Messenger Working Group at UHECR-2014 Conference
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