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IceCube sees astrophysical neutrinos

  1. Aug 23, 2015 #1

    marcus

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    http://inspirehep.net/record/1382926?ln=en
    PRL, 8 pages, 4 figures +supplementary material
    most neutrinos IceCube detects originated locally---e.g. from cosmic ray particles hitting Earth's atmosphere. But extra high energy neutrinos are more likely to come from outside solar system.
    As I understand it, they've been finding some rare ones that don't even come from in the plane of the Milkyway galaxy.
    http://nycity.today/content/284365-existence-cosmic-neutrinos-confirmed-help-antarctic-icecube-neutrino-observatory [Broken]
    rightly or not the headline in this popular media says "existence of cosmic neutrinos confirmed..."
     
    Last edited by a moderator: May 7, 2017
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  3. Aug 23, 2015 #2

    marcus

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    http://arxiv.org/abs/1507.07871
    IceCube at the Threshold
    Thomas K. Gaisser, for the IceCube Collaboration
    (Submitted on 28 Jul 2015)
    IceCube has observed neutrinos above 100 TeV at a level significantly above the steeply falling background of atmospheric neutrinos. The astrophysical signal is seen both in the high-energy starting event analysis from the whole sky and as a high-energy excess in the signal of neutrino-induced muons from below. No individual neutrino source, either steady or transient, has yet been identified. Several follow-up efforts are currently in place in an effort to find coincidences with sources observed by optical, X-ray and gamma-ray detectors. This paper, presented at the inauguration of HAWC, reviews the main results of IceCube and describes the status of plans to move to near-real time publication of high-energy events by IceCube.
    Presentation on behalf of IceCube at the Inauguration of HAWC, Puebla, March 19, 2015. Fifteen figures with updated references
     
  4. Aug 23, 2015 #3

    Bystander

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    Are there any alternative "local" sources?
     
  5. Aug 23, 2015 #4

    marcus

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    I hope some others will comment. I've been looking at Gaisser's article. This indicates that they have identified a particular small sample of neutrinos which are most likely of extragalactic origin. they have not identified specific sources, as yet. I hope you have a look at Gaisser http://arxiv.org/abs/1507.07871 and let us know what you make of it.
    ==quote pages 12-13 of Gaisser==
    Many, if not all, of the astrophysical events in the HESE sample are most likely of extragalactic origin. Ahlers & Halzen [39] show that, in this case, it is possible to use the observed luminosity density of the HESE flux (e.g. from Eq. 1) together with the upper limits from the point source search (Eq. 5) to constrain the classes of sources responsible for the astrophysical neutrino flux in IceCube. The argument is basically geometric, comparing the integral over the neutrinos from all sources in the Universe with the flux from a typical nearby source [40]. ...
    ...
    IceCube is currently in the position of having discovered high-energy astro- physical neutrinos without yet establishing what the sources are. Upper limits are placing significant constraints on particular classes of potential sources. For example, although blazars are attractive candidates [38], an analysis of the Fermi-LAT catalog of blazars [42] concludes that the sources in that catalog cannot count for more that about 20% of the observed astrophysical flux. Starburst galaxies [43] are an attractive potential class of sources, in part because of their relatively low luminosity and relatively high density. On the other hand, depending on how steeply the astrophysical spectrum extends to low energy [44], they may be in conflict with Fermi observations of the diffuse gamma-ray background [45]. ...
    ===endquote===
     
    Last edited: Aug 23, 2015
  6. Aug 24, 2015 #5

    Ken G

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    Perhaps now the question is, do you just wait longer for IceCube to compile more data, or do you build an instrument with more sensitivity? This would usher in a new branch of neutrino astrophysics.
     
  7. Aug 24, 2015 #6

    Drakkith

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    If we can string a few cups together, I'll build one in my bedroom.

    But seriously, what kind of phenomena can potentially give rise to 100 TeV neutrinos?
     
  8. Aug 24, 2015 #7

    Ken G

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    Generally the decay of other things that are easier to accelerate. I think a common reaction is high energy protons smack into something, creating pions, which decay in part into neutrinos. So the neutrinos are just kind of the slop left over from some really high-energy acceleration event. But 100 TeV isn't even all that much-- the highest energy cosmic rays are a million times more energetic than that-- so energetic that a single particle has the energy of a well-thrown baseball. The goal is to detect ZeV particles, though these must be quite rare!
     
  9. Aug 24, 2015 #8

    Drakkith

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    Thanks, Ken! I wouldn't have thought that they'd come from something as simple as a high-speed decaying particle!
     
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