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1.
  • Forskningsöversikt (refereegranskat)
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2.
  • Forskningsöversikt (refereegranskat)
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3.
  • Tidskriftsartikel (refereegranskat)
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4.
  • Aartsen, M. G., et al. (författare)
  • Multiwavelength follow-up of a rare IceCube neutrino multiplet
  • 2017
  • Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 607
  • Tidskriftsartikel (refereegranskat)abstract
    • On February 17, 2016, the IceCube real-time neutrino search identified, for the first time, three muon neutrino candidates arriving within 100 s of one another, consistent with coming from the same point in the sky. Such a triplet is expected once every 13.7 years as a random coincidence of background events. However, considering the lifetime of the follow-up program the probability of detecting at least one triplet from atmospheric background is 32%. Follow-up observatories were notified in order to search for an electromagnetic counterpart. Observations were obtained by Swift's X-ray telescope, by ASAS-SN, LCO and MASTER at optical wavelengths, and by VERITAS in the very-high-energy gamma-ray regime. Moreover, the Swift BAT serendipitously observed the location 100 s after the first neutrino was detected, and data from the Fermi LAT and HAWC observatory were analyzed. We present details of the neutrino triplet and the follow-up observations. No likely electromagnetic counterpart was detected, and we discuss the implications of these constraints on candidate neutrino sources such as gamma-ray bursts, core-collapse supernovae and active galactic nucleus flares. This study illustrates the potential of and challenges for future follow-up campaigns.
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5.
  • Adrian-Martinez, S., et al. (författare)
  • The First Combined Search For Neutrino Point-Sources In The Southern Hemisphere With The Antares And Icecube Neutrino Telescopes
  • 2016
  • Ingår i: ; 823:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of searches for point-like sources of neutrinos based on the first combined analysis of data from both the ANTARES and IceCube neutrino telescopes. The combination of both detectors, which differ in size and location, forms a window in the southern sky where the sensitivity to point sources improves by up to a factor of 2 compared with individual analyses. Using data recorded by ANTARES from 2007 to 2012, and by IceCube from 2008 to 2011, we search for sources of neutrino emission both across the southern sky and from a preselected list of candidate objects. No significant excess over background has been found in these searches, and flux upper limits for the candidate sources are presented for E-2.5 and E-2 power-law spectra with different energy cut-offs.
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6.
  • Aartsen, M. G., et al. (författare)
  • Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser IceCube instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 and 100 GeV, where a strong disappearance signal is expected. The IceCube detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by Delta m(32)(2) = 2.72(-0.20)(+0.19) x 10(-3) eV(2) and sin(2)theta(23) = 0.53(-0.12)(+0.09) (normal mass ordering assumed). The results are compatible, and comparable in precision, to those of dedicated oscillation experiments.
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7.
  • Aartsen, M. G., et al. (författare)
  • Multipole analysis of IceCube data to search for dark matter accumulated in the Galactic halo
  • 2015
  • Ingår i: European Physical Journal C. - 1434-6044 .- 1434-6052. ; 75:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Dark matter which is bound in the Galactic halo might self-annihilate and produce a flux of stable final state particles, e. g. high energy neutrinos. These neutrinos can be detected with IceCube, a cubic-kilometer sized Cherenkov detector. Given IceCube's large field of view, a characteristic anisotropy of the additional neutrino flux is expected. In this paper we describe a multipole method to search for such a large-scale anisotropy in IceCube data. This method uses the expansion coefficients of a multipole expansion of neutrino arrival directions and incorporates signal-specific weights for each expansion coefficient. We apply the technique to a high-purity muon neutrino sample from the Northern Hemisphere. The final result is compatible with the null-hypothesis. As no signal was observed, we present limits on the self-annihilation cross-section averaged over the relative velocity distribution down to 1.9x10(-23) cm(3) s(-1) for a dark matter particle mass of 700-1,000 GeV and direct annihilation into nu(nu) over bar. The resulting exclusion limits come close to exclusion limits from gamma-ray experiments, that focus on the outer Galactic halo, for high dark matter masses of a few TeV and hard annihilation channels.
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8.
  • Aartsen, M. G., et al. (författare)
  • Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data
  • 2014
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:10, s. 101101-
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for high-energy neutrinos interacting within the IceCube detector between 2010 and 2012 provided the first evidence for a high-energy neutrino flux of extraterrestrial origin. Results from an analysis using the same methods with a third year (2012-2013) of data from the complete IceCube detector are consistent with the previously reported astrophysical flux in the 100 TeV-PeV range at the level of 10(-8) GeV cm(-2) s(-1) sr(-1) per flavor and reject a purely atmospheric explanation for the combined three-year data at 5.7 sigma. The data are consistent with expectations for equal fluxes of all three neutrino flavors and with isotropic arrival directions, suggesting either numerous or spatially extended sources. The three-year data set, with a live time of 988 days, contains a total of 37 neutrino candidate events with deposited energies ranging from 30 to 2000 TeV. The 2000-TeV event is the highest-energy neutrino interaction ever observed.
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9.
  • Aartsen, M. G., et al. (författare)
  • SEARCHES FOR EXTENDED AND POINT-LIKE NEUTRINO SOURCES WITH FOUR YEARS OF ICECUBE DATA
  • 2014
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 796:2, s. 109-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present results on searches for point-like sources of neutrinos using four years of IceCube data, including the first year of data from the completed 86 string detector. The total livetime of the combined data set is 1373 days. For an E-2 spectrum, the observed 90% C. L. flux upper limits are similar to 10(-12) TeV-1 cm(-2) s(-1) for energies between 1 TeV and 1 PeV in the northern sky and similar to 10(-11) TeV-1 cm(-2) s(-1) for energies between 100 TeV and 100 PeV in the southern sky. This represents a 40% improvement compared to previous publications, resulting from both the additional year of data and the introduction of improved reconstructions. In addition, we present the first results from an all-sky search for extended sources of neutrinos. We update the results of searches for neutrino emission from stacked catalogs of sources and test five new catalogs; two of Galactic supernova remnants and three of active galactic nuclei. In all cases, the data are compatible with the background-only hypothesis, and upper limits on the flux of muon neutrinos are reported for the sources considered.
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10.
  • Aartsen, M. G., et al. (författare)
  • Searches for small-scale anisotropies from neutrino point sources with three years of IceCube data
  • 2015
  • Ingår i: Astroparticle physics. - 0927-6505 .- 1873-2852. ; 66, s. 39-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, IceCube found evidence for a diffuse signal of astrophysical neutrinos in an energy range of similar to 60 TeV to the PeV-scale [1]. The origin of those events, being a key to understanding the origin of cosmic rays, is still an unsolved question. So far, analyses have not succeeded to resolve the diffuse signal into point-like sources. Searches including a maximum-likelihood-ratio test, based on the reconstructed directions and energies of the detected down- and up-going neutrino candidates, were also performed on IceCube data leading to the exclusion of bright point sources. In this paper, we present two methods to search for faint neutrino point sources in three years of IceCube data, taken between 2008 and 2011. The first method is an autocorrelation test, applied separately to the northern and southern sky. The second method is a multipole analysis, which expands the measured data in the northern hemisphere into spherical harmonics and uses the resulting expansion coefficients to separate signal from background. With both methods, the results are consistent with the background expectation with a slightly more sparse spatial distribution, corresponding to an underfluctuation. Depending on the assumed number of sources, the resulting upper limit on the flux per source in the northern hemisphere for an E-2 energy spectrum ranges from similar to 1.5. 10(-8) GeV/cm(2) s(-1), in the case of one assumed source, to similar to 4. 10(-10) GeV/cm(2) s(-1), in the case of 3500 assumed sources.
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