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https://hdl.handle.net/2440/100896
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Type: | Journal article |
Title: | A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube |
Author: | Aartsen, M. Abraham, K. Ackermann, M. Adams, J. Aguilar, J. Ahlers, M. Ahrens, M. Altmann, D. Anderson, T. Archinger, M. Arguelles, C. Arlen, T. Auffenberg, J. Bai, X. Barwick, S. Baum, V. Bay, R. Beatty, J. Tjus, J. Becker, K. et al. |
Citation: | The Astrophysical Journal: an international review of astronomy and astronomical physics, 2015; 809(1):98-1-98-15 |
Publisher: | IOP Publishing |
Issue Date: | 2015 |
ISSN: | 0004-637X 1538-4357 |
Statement of Responsibility: | M. G. Aartsen ... G. C. Hill ... S. Robertson ... A. Wallace ... B. J. Whelan ... et al. (The IceCube Collaboration) |
Abstract: | Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for neutrino events with deposited energies ≥ 30 TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to lower energies and is also visible with throughgoing, νμ-induced tracks from the Northern Hemisphere. Here, we combine the results from six different IceCube searches for astrophysical neutrinos in a maximum-likelihood analysis. The combined event sample features high-statistics samples of shower-like and track-like events. The data are fit in up to three observables: energy, zenith angle, and event topology. Assuming the astrophysical neutrino flux to be isotropic and to consist of equal flavors at Earth, the all-flavor spectrum with neutrino energies between 25 TeV and 2.8 PeV is well described by an unbroken power law with best-fit spectral index −2.50 ± 0.09 and a flux at 100 TeV of $({6.7}_{-1.2}^{+1.1})\times {10}^{-18}\;{\mathrm{GeV}}^{-1}\;{{\rm{s}}}^{-1}\;{\mathrm{sr}}^{-1}\;{\mathrm{cm}}^{-2}$. Under the same assumptions, an unbroken power law with index −2 is disfavored with a significance of 3.8σ (p = 0.0066%) with respect to the best fit. This significance is reduced to 2.1σ (p = 1.7%) if instead we compare the best fit to a spectrum with index −2 that has an exponential cut-off at high energies. Allowing the electron-neutrino flux to deviate from the other two flavors, we find a νe fraction of 0.18 ± 0.11 at Earth. The sole production of electron neutrinos, which would be characteristic of neutron-decay-dominated sources, is rejected with a significance of 3.6σ (p = 0.014%). |
Keywords: | astroparticle physics; methods: data analysis; neutrinos |
Rights: | © 2015. The American Astronomical Society. All rights reserved. |
DOI: | 10.1088/0004-637X/809/1/98 |
Grant ID: | ARC |
Published version: | http://dx.doi.org/10.1088/0004-637x/809/1/98 |
Appears in Collections: | Aurora harvest 3 Physics publications |
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