* Astronomy

Title: Charm decay in slow-jet supernovae as the origin of the IceCube ultra-high energy neutrino events
Author: Atri Bhattacharya, Rikard Enberg, Mary Hall Reno, Ina Sarcevic

We investigate whether the recent ultra-high energy (UHE) neutrino events detected at the IceCube neutrino observatory could come from the decay of charmed mesons produced within the mildly relativistic jets of supernova-like astrophysical sources. We demonstrate that the 5.7sigma excess of neutrinos observed by IceCube in the energy range 30 TeV--2 PeV can be explained by a diffuse flux of neutrinos produced in such slow-jet supernovae, using the values of astrophysical and QCD parameters within the theoretical uncertainties associated with neutrino production from charmed meson decay in astrophysical sources. We discuss the theoretical uncertainties inherent in the evaluation of charm production in high energy hadronic collisions, as well as the astrophysical uncertainties associated with slow-jet supernova sources. The proton flux within the source, and therefore also the produced neutrino flux, is cut off at around a few PeV, when proton cooling processes become dominant over proton acceleration. This directly explains the sudden drop in event rates at energies above a few PeV. We incorporate the effect of energy dependence in the spectrum-weighted charm production cross-section and show that this has a very significant effect on the shape, magnitude and cut-off energies for the neutrino flux.

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Title: Neutrino signal from extended Galactic sources in IceCube
Authors: C. Tchernin, J.A. Aguilar, A. Neronov, T. Montaruli

We explore the detectability of the neutrino flux from the entire Galactic Plane or from a part of it with IceCube. We calculate the normalisation and the spectral index of the neutrino power law spectrum from different regions of the Galactic plane, based on the observed spectral characteristics of the pion decay gamma-ray diffuse emission observed by the Fermi/LAT telescope in the energy band above 100 GeV. We compare the neutrino flux calculated in this way with the sensitivity of IceCube for the detection of extended sources. Assuming a binned extended source analysis method, we find that the only possible evidence for neutrino emission for sources located in the Northern hemisphere is from the Cygnus region after 20 years of exposure. For other parts of the Galactic Plane even a 20 years exposure with IceCube is not sufficient for the detection. Taking into account marginal significance of the detectable source in the Cygnus region, we find a precise position and size of the source region which optimises the signal-to-noise ratio for neutrinos. We also calculate the low-energy threshold above which the neutrino signal could be detected with the highest signal-to-noise ratio. This calculation of precise source position, size and energy range, based on the gamma-ray data, could be used to remove the 'trial factor' in the analysis of the real neutrino data of IceCube. We notice that the diffuse neutrino emission from the inner Galactic Plane in the Southern Hemisphere is much brighter. A neutrino detector with characteristics equivalent to IceCube, but placed at the Northern Hemisphere (such as KM3NeT), would detect several isolated neutrino sources in the Galactic Plane within just 5 years exposure at 5{\sigma} level. These isolated sources of ~TeV neutrinos would unambiguously localise sources of cosmic rays which operated over the last 10 thousand years in the Galaxy.

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Neutrinos from the cosmos hint at new era in astronomy

An experiment buried beneath the ice of the South Pole has for the first time seen the particles called neutrinos originating outside our Solar System.
They are produced in our atmosphere and in the Universe's most violent processes, but the IceCube experiment has seen the first "cosmic neutrinos".
It detected 28 of the exceptionally fast-moving neutrinos - but it remains unclear exactly where they came from.
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Title: First observation of PeV-energy neutrinos with IceCube
Authors: IceCube Collaboration: M. G. Aartsen, R. Abbasi, Y. Abdou, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, D. Altmann, J. Auffenberg, X. Bai, M. Baker, S. W. Barwick, V. Baum, R. Bay, J. J. Beatty, S. Bechet, J. Becker Tjus, K.-H. Becker, M. Bell, M. L. Benabderrahmane, S. BenZvi, J. Berdermann, P. Berghaus, D. Berley, E. Bernardini, A. Bernhard, D. Bertrand, D. Z. Besson, G. Binder, D. Bindig, M. Bissok, E. Blaufuss, J. Blumenthal, D. J. Boersma, S. Bohaichuk, C. Bohm, D. Bose, S. Böser, O. Botner, L. Brayeur, H.-P. Bretz, A. M. Brown, R. Bruijn, J. Brunner, M. Carson, J. Casey, M. Casier, D. Chirkin, A. Christov, B. Christy, K. Clark, F. Clevermann, S. Coenders, S. Cohen, D. F. Cowen, A. H. Cruz Silva, M. Danninger, J. Daughhetee, J. C. Davis, C. De Clercq, S. De Ridder, P. Desiati, et al. (221 additional authors not shown)

We report on the observation of two neutrino-induced events which have an estimated deposited energy in the IceCube detector of 1.04 ± 0.16 and 1.14 ± 0.17 PeV, respectively, the highest neutrino energies observed so far. These events are consistent with fully contained particle showers induced by neutral-current \nu_{e, µ,\tau} (\bar\nu_{e, µ,\tau}) or charged-current \nu_{e} (\bar\nu_{e}) interactions within the IceCube detector. The events were discovered in a search for ultra-high energy neutrinos using data corresponding to 615.9 days effective livetime. The two neutrino events are observed over an expected atmospheric background of 0.082 ± 0.004 {(stat)}^{+0.041}_{-0.057} {(syst)}. The resulting p-value for the background-only hypothesis is 2.9 x 10^{-3} (2.8\sigma) taking into account the uncertainty on the expected number of background events. Though the two events could be a first indication of an astrophysical neutrino flux, the moderate significance and the uncertainties on the expected atmospheric background from neutrinos produced in the decay of charmed mesons do not allow for a firm conclusion at this point.

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