1,895 research outputs found
Multi-PeV Signals from a New Astrophysical Neutrino Flux Beyond the Glashow Resonance
The IceCube neutrino discovery was punctuated by three showers with ~
1-2 PeV. Interest is intense in possible fluxes at higher energies, though a
marked deficit of ~ 6 PeV Glashow resonance events implies a spectrum
that is soft and/or cutoff below ~few PeV. However, IceCube recently reported a
through-going track event depositing 2.6 0.3 PeV. A muon depositing so
much energy can imply 10 PeV. We show that extending the
soft spectral fit from TeV-PeV data is unlikely to yield such an
event. Alternatively, a tau can deposit this much energy, though requiring
~10x higher. We find that either scenario hints at a new flux,
with the hierarchy of and energies suggesting a window
into astrophysical neutrinos at ~ 100 PeV if a tau. We address
implications, including for ultrahigh-energy cosmic-ray and neutrino origins.Comment: 6 pages, 4 figures + 3 pages Supplementary Material; updated to agree
with version published in Physical Review Letter
The Cosmic MeV Neutrino Background as a Laboratory for Black Hole Formation
Calculations of the cosmic rate of core collapses, and the associated
neutrino flux, commonly assume that a fixed fraction of massive stars collapse
to black holes. We argue that recent results suggest that this fraction instead
increases with redshift. With relatively more stars vanishing as "unnovae" in
the distant universe, the detectability of the cosmic MeV neutrino background
is improved due to their hotter neutrino spectrum, and expectations for
supernova surveys are reduced. We conclude that neutrino detectors, after the
flux from normal SNe is isolated via either improved modeling or the next
Galactic SN, can probe the conditions and history of black hole formation.Comment: 5 pages, 4 figures; Matches version published in Physics Letters
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