Spectral analysis of the high-energy IceCube neutrinos

Abstract

A full energy and flavor-dependent analysis of the three-year high-energy IceCube neutrino events is presented. By means of multidimensional fits, we derive the current preferred values of the highenergy neutrino flavor ratios, the normalization and spectral index of the astrophysical fluxes, and the expected atmospheric background events, including a prompt component. A crucial assumption resides on the choice of the energy interval used for the analyses, which significantly biases the results. When restricting ourselves to the ∼30 TeV−3 PeV energy range, which contains all the observed IceCube events, we find that the inclusion of the spectral information improves the fit to the canonical flavor composition at Earth, (1 : 1 : 1)⊕, with respect to a single-energy bin analysis. Increasing both the minimum and the maximum deposited energies has dramatic effects on the reconstructed flavor ratios as well as on the spectral index. Imposing a higher threshold of 60 TeV yields a slightly harder spectrum by allowing a larger muon neutrino component, since above this energy most atmospheric tracklike events are effectively removed. Extending the high-energy cutoff to fully cover the Glashow resonance region leads to a softer spectrum and a preference for tau neutrino dominance, as none of the expected electron antineutrino induced showers have been observed so far. The lack of showers at energies above 2 PeV may point to a broken power-law neutrino spectrum. Future data may confirm or falsify whether or not the recently discovered high-energy neutrino fluxes and the long-standing detected cosmic rays have a common origin.PACS numbers: 95.85. Ry, 14.60.Pq, 95.55.Vj, 29.40.Ka

Searching for leptoquarks at IceCube and the LHC

“…A parametrization of this function can be found in Ref. [68]. Though IceCube provides effective masses as a function of the incoming neutrino energies, these depend implicitly on the ν − N cross sections: since we are searching for effects of new physics, the method of Eq.…”

“…We calculate the number of events at IceCube following the formalism laid out in [68]. The relevant observable at IceCube is the event rate per deposited electromagnetic (EM)-equivalent energy.…”

“…To properly take this into account, one should compute the directionally dependent attenuation rate by solving the transport equation. We will use angleaveraged attenuation rates computed by [68]; Ref. [57] has shown that the impact of LQs on attenuation is quite small.…”

Astrophysical neutrinos flavored with beyond the Standard Model physics

“…A complete analysis of spectrum, neutrino flux normalization and flavor composition is, for example, given in Refs. [42][43][44].…”

Test of Lorentz Violation with Astrophysical Neutrino Flavor

“…Finding the flavor ratio is experimentally challenging 17 , due especially to the separation of ν e and ν τ largely relying on the simulation input 18 . The measurements can be improved with current detectors, but future IceCubeGen2 19 and KM3NeT 20 will have a better chance of studying the astrophysical neutrino flavors from their superior detectors.…”