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  • 51.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Systemfysik.
    Burgess, Christin
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hundertmark, Stephan
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Thollander, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    The Search for Muon Neutrinos from Northern Hemisphere Gamma-Ray Bursts with AMANDA2008Inngår i: Astrophysical Journal, nr 674, s. 357-370Artikkel i tidsskrift (Fagfellevurdert)
  • 52.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hundertmark, Stephan
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wiedemann, Christin
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Search for Point Sources of High Energy Neutrinos with Final Data from AMANDA-II2009Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 79, s. 062001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a search for point sources of high energy neutrinos using 3.8 yr of data recorded by AMANDA-II during 2000–2006. After reconstructing muon tracks and applying selection criteria designed to optimally retain neutrino-induced events originating in the northern sky, we arrive at a sample of 6595 candidate events, predominantly from atmospheric neutrinos with primary energy 100 GeV to 8 TeV. Our search of this sample reveals no indications of a neutrino point source. We place the most stringent limits to date on E-2 neutrino fluxes from points in the northern sky, with an average upper limit of E2Φνμτ≤5.2×10-11  TeV cm-2 s-1 on the sum of νμ and ντ fluxes, assumed equal, over the energy range from 1.9 TeV to 2.5 PeV.

  • 53.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Systemfysik.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hundertmark, Stephan
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Wiedemann, Christin
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Solar Energetic Particle Spectrum on 13 December 2006 Determined by IceTop2008Inngår i: Astrophysical Journal Letters, nr 689, s. L65-L68Artikkel i tidsskrift (Fagfellevurdert)
  • 54.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Systemfysik.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Hundertmark, Stephan
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Thollander, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Wiedemann, Christin
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Elementarpartikelfysik.
    Search for Ultra High-Energy Neutrinos with AMANDA-II2008Inngår i: Astrophysical Journal, nr 675, s. 1014-1024Artikkel i tidsskrift (Fagfellevurdert)
  • 55.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nygren, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Determination of the Atmospheric Neutrino Flux and Searches for New Physics with AMANDA-II2009Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 79, s. 102005-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The AMANDA-II detector, operating since 2000 in the deep ice at the geographic South Pole, has accumulated a large sample of atmospheric muon neutrinos in the 100 GeV to 10 TeVenergy range. The zenith angle and energy distribution of these events can be used to search for various phenomenological signatures of quantum gravity in the neutrino sector, such as violation of Lorentz invariance or quantum decoherence. Analyzing a set of 5511 candidate neutrino events collected during 1387 days of livetime from 2000 to 2006, we find no evidence for such effects and set upper limits on violation of Lorentz invariance and quantum decoherence parameters using a maximum likelihood method. Given the absenceof evidence for new flavor-changing physics, we use the same methodology to determine the conventionalatmospheric muon neutrino flux above 100 GeV.

  • 56.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nygren, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Search for High-Energy Muon Neutrinos from the "Naked-Eye" GRB 080319B with the IceCube Neutrino Telescope2009Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 701, s. 1721-1731Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a search with the IceCube detector for high-energy muon neutrinos from GRB 080319B, one of the brightest gamma-ray bursts (GRBs) ever observed. The fireball model predicts that a mean of 0.1 events should be detected by IceCube for a bulk Lorentz boost of the jet of 300. In both the direct on-time window of 66 s and an extended window of about 300 s around the GRB, no excess was found above background. The 90% CL upper limit on the number of track-like events from the GRB is 2.7, corresponding to a muon neutrino fluence limit of 9.5 × 10–3 erg cm–2 in the energy range between 120 TeV and 2.2 PeV, which contains 90% of the expected events.

  • 57.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wiedemann, Christin
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    The IceCube Data Acquisition System: Signal Capture, Digitization, and Timestamping2009Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 601, s. 294-316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs), detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, functional capabilities, and initial performance of the DOM MB, and the operation of a combined array of DOMs as a system, are described here. Experience with the first InIce strings and the IceTop stations indicates that the system design and performance goals have been achieved.

    Keywords:

  • 58.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Limits on a Muon Flux from Neutralino Annihilations in the Sun with the IceCube 22-string Detector2009Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, s. 201302-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for muon neutrinos from neutralino annihilations in the Sun has been performed with the IceCube 22-string neutrino detector using data collected in 104.3 days of live time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured neutralinos in the Sun and converted to limits on the weakly interacting massive particle (WIMP) proton cross sections for WIMP masses in the range 250–5000 GeV. These results are the most stringent limits to date on neutralino annihilation in the Sun.

  • 59.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Flis, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Multiyear Search for Dark Matter Annihilations in the Sun with the AMANDA-II and IceCube Detectors2012Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 85, s. 042002-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for an excess of muon neutrinos from dark matter annihilations in the Sun has been performed with the AMANDA-II neutrino telescope using data collected in 812 days of live time between 2001 and 2006 and 149 days of live time collected with the AMANDA-II and the 40-string configuration of IceCube during 2008 and early 2009. No excess over the expected atmospheric neutrino background has been observed. We combine these results with the previously published IceCube limits obtained with data taken during 2007 to obtain a total live time of 1065 days. We provide an upper limit at 90% confidence level on the annihilation rate of captured neutralinos in the Sun, as well as the corresponding muon flux limit at the Earth, both as functions of the neutralino mass in the range 50–5000 GeV. We also derive a limit on the neutralino-proton spin-dependent and spin-independent cross section. The limits presented here improve the previous results obtained by the collaboration between a factor of 2 and 5, as well as extending the neutralino masses probed down to 50 GeV. The spin-dependent cross section limits are the most stringent so far for neutralino masses above 200 GeV, and well below direct search results in the mass range from 50 GeV to 5 TeV.

  • 60.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Flis, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per-Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wolf, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Measurement of South Pole ice transparency with the IceCube LED calibration system2013Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 711, s. 73-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The IceCube Neutrino Observatory, approximately 1 km(3) in size, is now complete with 86 strings deployed in the Antarctic ice. IceCube detects the Cherenkov radiation emitted by charged particles passing through or created in the ice. To realize the full potential of the detector, the properties of light propagation in the ice in and around the detector must be well understood. This report presents a new method of fitting the model of light propagation in the ice to a data set of in situ light source events collected with IceCube. The resulting set of derived parameters, namely the measured values of scattering and absorption coefficients vs. depth, is presented and a comparison of IceCube data with simulations based on the new model is shown.

  • 61.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nygren, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    The Energy Spectrum of Atmospheric Neutrinos between 2 and 200 TeV with the AMANDA-II Detector2010Inngår i: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 34, s. 48-58Artikkel i tidsskrift (Fagfellevurdert)
  • 62.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Background Studies for Acoustic Neutrino Detection at the South Pole2012Inngår i: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 35, s. 312-324Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The detection of acoustic signals from ultra-high energy neutrino interactions is a promising method to measure the flux of cosmogenic neutrinos expected on Earth. The energy threshold for this process depends strongly on the absolute noise level in the target material. The South Pole Acoustic Test Setup (SPATS), deployed in the upper part of four boreholes of the IceCube Neutrino Observatory, has monitored the noise in Antarctic ice at the geographic South Pole for more than two years down to 500 m depth. The noise is very stable and Gaussian distributed. Lacking an in situ calibration up to now, laboratory measurements have been used to estimate the absolute noise level in the 10–50 kHz frequency range to be smaller than 20 mPa. Using a threshold trigger, sensors of the South Pole Acoustic Test Setup registered acoustic events in the IceCube detector volume and its vicinity. Acoustic signals from refreezing IceCube holes and from anthropogenic sources have been used to test the localization of acoustic events. An upper limit on the neutrino flux at energies Eν > 1011 GeV is derived from acoustic data taken over eight months.

  • 63.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Constraints on the Extremely-high Energy Cosmic Neutrino Flux with the IceCube 2008-2009 Data2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, nr 9, s. 092003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a search for extremely-high energy neutrinos with energies greater than 10(6) GeV using the data taken with the IceCube detector at the South Pole. The data was collected between April 2008 and May 2009 with the half-completed IceCube array. The absence of signal candidate events in the sample of 333.5 days of live time significantly improves model-independent limits from previous searches and allows to place a limit on the diffuse flux of cosmic neutrinos with an E(-2) spectrum in the energy range 2.0 x 10(6) - 6.3 x 10(9) GeV to a level of E(2) phi <= 3.6 x 10(-8) GeV cm(-2) sec(-1) sr(-1).

  • 64.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    First Search for Atmospheric and Extraterrestrial Neutrino-Induced Cascades with the IceCube Detector2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, nr 7, s. 072001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. A total of 14 events with energies above 16 TeV remained after event selections in the diffuse analysis, with an expected total background contribution of 8.3 +/- 3.6. At 90% confidence we set an upper limit of E(2)Phi(90%CL) < 3.6 x 10(-7) GeV.cm(-2).s(-1).sr(-1) on the diffuse flux of neutrinos of all flavors in the energy range between 24 TeV and 6.6 PeV assuming that Phi proportional to E(-2) and the flavor composition of the nu(e):nu(mu):nu(tau) flux is 1:1:1 at the Earth. The atmospheric neutrino analysis was optimized for lower energies. A total of 12 events were observed with energies above 5 TeV. The observed number of events is consistent with the expected background, within the uncertainties.

  • 65.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Limits on Neutrino Emission from Gamma-Ray Bursts with the 40 String IceCube Detector2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, nr 14, s. 141101-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18) eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from p gamma interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.

  • 66.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Search for Dark Matter from the Galactic Halo with the IceCube Neutrino Telescope2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, nr 2, s. 022004-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Self-annihilating or decaying dark matter in the Galactic halo might produce high energy neutrinos detectable with neutrino telescopes. We have conducted a search for such a signal using 276 days of data from the IceCube 22-string configuration detector acquired during 2007 and 2008. The effect of halo model choice in the extracted limit is reduced by performing a search that considers the outer halo region and not the Galactic Center. We constrain any large-scale neutrino anisotropy and are able to set a limit on the dark matter self-annihilation cross section of h <sigma(A)nu > similar or equal to 10(-22) cm(3) s(-1) for weakly interacting massive particle masses above 1 TeV, assuming a monochromatic neutrino line spectrum.

  • 67.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Time-Integrated Searches for Point-like Sources of Neutrinos with the 40-String IceCube Detector2011Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 732, nr 1, s. 18-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the results of time-integrated searches for astrophysical neutrino sources in both the northern and southern skies. Data were collected using the partially completed IceCube detector in the 40-string configuration recorded between 2008 April 5 and 2009 May 20, totaling 375.5 days livetime. An unbinned maximum likelihood ratio method is used to search for astrophysical signals. The data sample contains 36,900 events: 14,121 from the northern sky, mostly muons induced by atmospheric neutrinos, and 22,779 from the southern sky, mostly high-energy atmospheric muons. The analysis includes searches for individual point sources and stacked searches for sources in a common class, sometimes including a spatial extent. While this analysis is sensitive to TeV-PeV energy neutrinos in the northern sky, it is primarily sensitive to neutrinos with energy greater than about 1 PeV in the southern sky. No evidence for a signal is found in any of the searches. Limits are set for neutrino fluxes from astrophysical sources over the entire sky and compared to predictions. The sensitivity is at least a factor of two better than previous searches (depending on declination), with 90% confidence level muon neutrino flux upper limits being between E(2)d Phi/dE similar to 2-200 x 10(-12) TeV cm(-2) s(-1) in the northern sky and between 3-700 x 10(-12) TeV cm(-2) s(-1) in the southern sky. The stacked source searches provide the best limits to specific source classes. The full IceCube detector is expected to improve the sensitivity to d Phi/dE proportional to E(-2) sources by another factor of two in the first year of operation.

  • 68.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Calibration and Characterization of the IceCube Photomultiplier Tube2010Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 618, s. 139-152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Over 5000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-in. diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts

  • 69.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Constraints on High-Energy Neutrino Emission from SN 2008D2011Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 527, s. A28-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    SN 2008D, a core collapse supernova at a distance of 27 Mpc, was serendipitously discovered by the Swift satellite through an associated X-ray flash. Core collapse supernovae have been observed in association with long gamma-ray bursts and X-ray flashes and a physical connection is widely assumed. This connection could imply that some core collapse supernovae possess mildly relativistic jets in which high-energy neutrinos are produced through proton-proton collisions. The predicted neutrino spectra would be detectable by Cherenkov neutrino detectors like IceCube. A search for a neutrino signal in temporal and spatial correlation with the observed X-ray flash of SN 2008D was conducted using data taken in 2007–2008 with 22 strings of the IceCube detector. Events were selected based on a boosted decision tree classifier trained with simulated signal and experimental background data. The classifier was optimized to the position and a “soft jet” neutrino spectrum assumed for SN 2008D. Using three search windows placed around the X-ray peak, emission time scales from 100–10 000 s were probed. No events passing the cuts were observed in agreement with the signal expectation of 0.13 events. Upper limits on the muon neutrino flux from core collapse supernovae were derived for different emission time scales and the principal model parameters were constrained. While no meaningful limits can be given in the case of an isotropic neutrino emission, the parameter space for a jetted emission can be constrained. Future analyses with the full 86 string IceCube detector could detect up to  ~100 events for a core-collapse supernova at 10 Mpc according to the soft jet model.

  • 70.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Extending the Search for Neutrino Point Sources with IceCube above the Horizon2009Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, s. 221102-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Point source searches with the IceCube neutrino telescope have been restricted to one hemisphere, due to the exclusive selection of upward going events as a way of rejecting the atmospheric muon background. We show that the region above the horizon can be included by suppressing the background through energy-sensitive cuts. This improves the sensitivity above PeV energies, previously not accessible for declinations of more than a few degrees below the horizon due to the absorption of neutrinos in Earth. We present results based on data collected with 22 strings of IceCube, extending its field of view and energy reach for point source searches. No significant excess above the atmospheric background is observed in a sky scan and in tests of source candidates. Upper limits are reported, which for the first time cover point sources in the southern sky up to EeV energies

  • 71.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Limits on a Muon Flux from Kaluza-Klein Dark Matter Annihilations  in the Sun from the IceCube 22-string Detector2010Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 81, nr 5, s. 057101-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for muon neutrinos from Kaluza-Klein dark matter annihilations in the Sun has been performed with the 22-string configuration of the IceCube neutrino detector using data collected in 104.3 days of live time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured lightest Kaluza-Klein particle (LKP) WIMPs in the Sun and converted to limits on the LKP-proton cross sections for LKP masses in the range 250-3000 GeV. These results are the most stringent limits to date on LKP annihilation in the Sun.

  • 72.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Measurement of Acoustic Attenuation in South Pole Ice2011Inngår i: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 34, nr 6, s. 382-393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient α = 3.20 ± 0.57 km−1 between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for λ ≡ 1/α of ∼300 m with 20% uncertainty. No significant depth or frequency dependence has been found.

  • 73.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Measurement of the Anisotropy of Cosmic Ray Arrival Directions with IceCube2010Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 718, s. L194-L198Artikkel i tidsskrift (Fagfellevurdert)
  • 74.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Measurement of the Atmospheric Neutrino Energy Spectrum from 100 GeV to 400 TeV with IceCube2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, nr 1, s. 012001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18 000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject misreconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than 1%. This is the first measurement of atmospheric neutrinos up to 400 TeV, and is fundamental to understanding the impact of this neutrino background on astrophysical neutrino observations with IceCube. The measured spectrum is consistent with predictions for the atmospheric nu(mu) + (nu) over bar (mu) flux.

  • 75.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Search for a Lorentz-Violating Sidereal Signal with Atmospheric Neutrinos in IceCube2010Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 82, s. 112003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillation models, derivable from extensions to the standard model, allow for neutrino oscillations that depend on the neutrino’s direction of propagation. No such direction-dependent variation was found. A discrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Because of the unique high energy reach of IceCube, it was possible to improve constraints on certain Lorentz-violating oscillations by 3 orders of magnitude with respect to limits set by other experiments

  • 76.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Search for Neutrino-Induced Cascades with Five Years of AMANDA Data2011Inngår i: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 34, nr 6, s. 420-430Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the search for electromagnetic and hadronic showers ("cascades") produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were recorded during 1001 days of detector livetime in the years 2000-2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of v(e):v(mu):v(tau) = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Phi proportional to E(-2) is less than 5.0 x 10(-7) GeV s(-1) sr(-1) cm(-2) at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production.

  • 77.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Search for Relativistic Magnetic Monopoles with the AMANDA-II Neutrino Telescope2010Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 69, nr 3-4, s. 361-378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the search for Cherenkov signatures from relativistic magnetic monopoles in data taken with the AMANDA-II detector, a neutrino telescope deployed in the Antarctic ice cap at the Geographic South Pole. The non-observation of a monopole signal in data collected during the year 2000 improves present experimental limits on the flux of relativistic magnetic monopoles: Our flux limit varies between 3.8×10−17 cm−2 s−1 sr−1 (for monopoles moving at the vacuum speed of light) and 8.8×10−16 cm−2 s−1 sr−1 (for monopoles moving at a speed β=v/c=0.76, just above the Cherenkov threshold in ice). These limits apply to monopoles that are energetic enough to penetrate the Earth and enter the detector from below the horizon. The limit obtained for monopoles reaching the detector from above the horizon is less stringent by roughly an order of magnitude, due to the much larger background from down-going atmospheric muons. This looser limit is however valid for a larger class of magnetic monopoles, since the monopoles are not required to pass through the Earth.

  • 78.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    The First Search for Extremely-High Energy Cosmogenic Neutrinos with the IceCube Neutrino Observatory2010Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 82, nr 7, s. 072003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the results of the search for extremely-high energy neutrinos with energies above 107  GeV obtained with the partially (∼30%) constructed IceCube in 2007. From the absence of signal events in the sample of 242.1 days of effective live time, we derive a 90% C.L. model independent differential upper limit based on the number of signal events per energy decade at E2ϕνe+νμ+ντ≃1.4×10-6  GeV cm-2 sec⁡-1 sr-1 for neutrinos in the energy range from 3×107 to 3×109  GeV.

  • 79.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    IceCube Sensitivity for Low-Energy Neutrinos from Nearby Supernovae2011Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 535, s. A109-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the response of the IceCube neutrino telescope located at the geographic south pole to outbursts of MeV neutrinos from the core collapse of nearby massive stars. IceCube was completed in December 2010 forming a lattice of 5160 photomultiplier tubes that monitor a volume of similar to 1 km(3) in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can detect subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed, as well as the possibility to detect the neutronization burst, a short outbreak of nu(e)'s released by electron capture on protons soon after collapse. Tantalizing signatures, such as the formation of a quark star or a black hole as well as the characteristics of shock waves, are investigated to illustrate IceCube's capability for supernova detection.

  • 80.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Neutrino Analysis of the 2010 September Crab Nebula Flare and Time-Integrated Constraints on Neutrino Emission from the Crab using IceCube2012Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 745, nr 1, s. 45-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the results of a search for high-energy muon neutrinos with the IceCube detector in coincidence with the Crab Nebula flare reported on 2010 September by various experiments. Due to the unusual flaring state of the otherwise steady source we performed a prompt analysis of the 79-string configuration data to search for neutrinos that might be emitted along with the observed γ-rays. We performed two different and complementary data selections of neutrino events in the time window of 10 days around the flare. One event selection is optimized for discovery of E –2 ν neutrino spectrum typical of first-order Fermi acceleration. A similar event selection has also been applied to the 40-string data to derive the time-integrated limits to the neutrino emission from the Crab. The other event selection was optimized for discovery of neutrino spectra with softer spectral index and TeV energy cutoffs as observed for various Galactic sources in γ-rays. The 90% confidence level (CL) best upper limits on the Crab flux during the 10 day flare are 4.73 × 10–11 cm–2 s–1 TeV–1 for an E –2 ν neutrino spectrum and 2.50 × 10–10 cm–2 s–1 TeV–1 for a softer neutrino spectra of E –2.7 ν, as indicated by Fermi measurements during the flare. In this paper, we also illustrate the impact of the time-integrated limit on the Crab neutrino steady emission. The limit obtained using 375.5 days of the 40-string configuration is compared to existing models of neutrino production from the Crab and its impact on astrophysical parameters is discussed. The most optimistic predictions of some models are already rejected by the IceCube neutrino telescope with more than 90% CL.

  • 81.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Observation of Anisotropy in the Arrival Directions of Galactic Cosmic Rays at Multiple Angular Scales with IceCube2011Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 740, nr 1, s. 16-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Between 2009 May and 2010 May, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mil anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of five weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at (right ascension alpha = 122 degrees.4 and declination d = -47 degrees.4), extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.

  • 82.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Observation of Anisotropy in the Galactic Cosmic-Ray Arrival Directions at 400 TeV with IceCube2012Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 746, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic-ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic-ray-induced muons recorded by the partially deployed IceCube observatory between 2009 May and 2010 May. The data include a total of 33 x 10(9) muon events with a median angular resolution of similar to 3 degrees. A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic-ray median energies of 20 and 400 TeV. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high-energy sky map shows a different anisotropy structure including a deficit with a post-trial significance of -6.3 sigma. This anisotropy reveals a new feature of the Galactic cosmic-ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

  • 83.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Search for a Diffuse Flux of Astrophysical Muon Neutrinos with the IceCube 40-String Detector2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, nr 8, s. 082001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The IceCube Neutrino Observatory is a 1 km(3) detector currently taking data at the South Pole. One of the main strategies used to look for astrophysical neutrinos with IceCube is the search for a diffuse flux of high-energy neutrinos from unresolved sources. A hard energy spectrum of neutrinos from isotropically distributed astrophysical sources could manifest itself as a detectable signal that may be differentiated from the atmospheric neutrino background by spectral measurement. This analysis uses data from the IceCube detector collected in its half completed configuration which operated between April 2008 and May 2009 to search for a diffuse flux of astrophysical muon neutrinos. A total of 12 877 upward-going candidate neutrino events have been selected for this analysis. No evidence for a diffuse flux of astrophysical muon neutrinos was found in the data set leading to a 90% C. L. upper limit on the normalization of an E(-2) astrophysical nu(mu) flux of 8.9 x 10(-9) GeV cm(-2) s(-1) sr(-1). The analysis is sensitive in the energy range between 35 TeV and 7 PeV. The 12 877 candidate neutrino events are consistent with atmospheric muon neutrinos measured from 332 GeV to 84 TeV and no evidence for a prompt component to the atmospheric neutrino spectrum is found.

  • 84.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Searching for soft relativistic jets in core-collapse supernovae with the IceCube optical follow-up program2012Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 539, s. A60-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Transient neutrino sources such as gamma-ray bursts (GRBs) and supernovae (SNe) are hypothesized to emit bursts of high-energy neutrinos on a time-scale of less than or similar to 100 s. While GRB neutrinos would be produced in high relativistic jets, core-collapse SNe might host soft-relativistic jets, which become stalled in the outer layers of the progenitor star leading to an efficient production of high-energy neutrinos. Aims. To increase the sensitivity to these neutrinos and identify their sources, a low-threshold optical follow-up program for neutrino multiplets detected with the IceCube observatory has been implemented. Methods. If a neutrino multiplet, i.e. two or more neutrinos from the same direction within 100 s, is found by IceCube a trigger is sent to the Robotic Optical Transient Search Experiment, ROTSE. The 4 ROTSE telescopes immediately start an observation program of the corresponding region of the sky in order to detect an optical counterpart to the neutrino events. Results. No statistically significant excess in the rate of neutrino multiplets has been observed and furthermore no coincidence with an optical counterpart was found. Conclusions. The search allows, for the first time, to set stringent limits on current models predicting a high-energy neutrino flux from soft relativistic hadronic jets in core-collapse SNe. We conclude that a sub-population of SNe with typical Lorentz boost factor and jet energy of 10 and 3 x 1051 erg, respectively, does not exceed 4.2% at 90% confidence.

  • 85.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Finley, Chad
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Zoll, Marcel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Time-Dependent Searches for Point Sources of Neutrinos with the 40-String and 22-String Configurations of IceCube2012Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 744, nr 1, s. 1-Artikkel i tidsskrift (Fagfellevurdert)
  • 86.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nygren, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    First Neutrino Point-Source Results From the 22 String IceCube Detector2009Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 701, s. L47-L51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present new results of searches for neutrino point sources in the northern sky, using data recorded in 2007-2008 with 22 strings of the IceCube detector (approximately one-fourth of the planned total) and 275.7 days of live time. The final sample of 5114 neutrino candidate events agrees well with the expected background of atmospheric muon neutrinos and a small component of atmospheric muons. No evidence of a point source is found, with the most significant excess of events in the sky at 2.2σ after accounting for all trials. The average upper limit over the northern sky for point sources of muon-neutrinos with E –2 spectrum is , in the energy range from 3 TeV to 3 PeV, improving the previous best average upper limit by the AMANDA-II detector by a factor of 2.

  • 87.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Danninger, Matthias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nygren, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Measurement of Sound Speed vs Depth in South Pole Ice for Neutrino Astronomy2010Inngår i: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 33, s. 277-286Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at 5–25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.

  • 88.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hellman, Sten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hidvegi, Attila
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    ATLAS Level-1 Calorimeter Trigger: Subsystem Tests of a Jet/Energy-sum Processor Module2004Inngår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, nr 5, s. 2356-2361Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS Level-1 Calorimeter Trigger consists of a Preprocessor, a Cluster Processor (CP), and a Jet/Energy-sum Processor (JEP). The CP and JEP receive digitized trigger-tower data from the Preprocessor and produce trigger multiplicities and total and missing energy for the final trigger decision. The trigger also provides region-of-interest information for the Level-2 trigger and intermediate results of the data acquisition system for monitoring and diagnostics by using Readout Driver modules. The JEP identifies and localizes jets, and sums total and missing transverse energy information from the trigger data. The Jet/Energy Module (JEM) is the main module of the JEP. The JEM prototype is designed to be functionally identical to the final production module for ATLAS and to have the full number of channels. Three JEM prototypes have been built and successfully tested. Various test vector patterns were used to test the energy summation and the jet algorithms. Data communication between adjacent JEMs and all other relevant modules of the JEP has been tested. Recent test results using the JEM prototypes are discussed.

  • 89.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hellman, Sten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hidvegi, Attila
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pre-Production Validation of the ATLAS Level-1 Calorimeter Trigger System2006Inngår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, nr 3, s. 859-863Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Level-1 Calorimeter Trigger is a major part of the first stage of event selection for the ATLAS experiment at the LHC. It is a digital, pipelined system with several stages of processing, largely based on FPGAs, which perform programmable algorithms in parallel with a fixed latency to process about 300 Gbyte/s of input data. The real-time output consists of counts of different types of trigger objects and energy sums. Prototypes of all module types have been undergoing intensive testing before final production during 2005. Verification of their correct operation has been performed stand-alone and in the ATLAS test-beam at CERN. Results from these investigations will be presented, along with a description of the methodology used to perform the tests.

  • 90.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hellman, Sten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hidvegi, Attila
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    The ATLAS Level-1 Calorimeter Trigger Architecture2004Inngår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, nr 3, s. 356-360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The architecture of the ATLAS Level-1 Calorimeter Trigger system (L1Calo) is presented. Common approaches have been adopted for data distribution, result merging, readout, and slow control across the three different subsystems. A significant amount of common hardware is utilized, yielding substantial savings in cost, spares, and development effort. A custom, high-density backplane has been developed with data paths suitable for both the em/τ cluster processor (CP) and jet/energy-summation processor (JEP) subsystems. Common modules also provide interfaces to VME, CANbus and the LHC timing, trigger and control system (TTC). A common data merger module (CMM) uses field-programmable gate arrays (FPGAs) with multiple configurations for summing electron/photon and τ/hadron cluster multiplicities, jet multiplicities, or total and missing transverse energy. The CMM performs both crate- and system-level merging. A common, FPGA-based readout driver (ROD) is used by all of the subsystems to send input, intermediate and output data to the data acquisition (DAQ) system, and region-of-interest (RoI) data to the level-2 triggers. Extensive use of FPGAs throughout the system makes the trigger flexible and upgradable, and several architectural choices have been made to reduce the number of intercrate links and make the hardware more robust.

  • 91.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hulth, Per Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Hultqvist, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Johansson, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Nygren, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Seo, Seon-Hee
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Walck, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Wikström, Gustav
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
    Search for Muon Neutrinos from Gamma-Ray Bursts with the IceCube Neutrino Telescope2010Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 710, nr 1, s. 346-359Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the results of searches for high-energy muon neutrinos from 41 gamma-ray bursts (GRBs) in the northern sky with the IceCube detector in its 22 string configuration active in 2007/2008. The searches cover both the prompt and a possible precursor emission as well as a model-independent, wide time window of -1 hr to + 3 hr around each GRB. In contrast to previous searches with a large GRB population, we do not utilize a standard Waxman-Bahcall GRB flux for the prompt emission but calculate individual neutrino spectra for all 41 GRBs from the burst parameters measured by satellites. For all of the three time windows, the best estimate for the number of signal events is zero. Therefore, we place 90% CL upper limits on the fluence from the prompt phase of 3.7 x 10(-3) erg cm(-2) (72 TeV-6.5 PeV) and on the fluence from the precursor phase of 2.3 x 10(-3) erg cm(-2) (2.2-55 TeV), where the quoted energy ranges contain 90% of the expected signal events in the detector. The 90% CL upper limit for the wide time window is 2.7 x 10(-3) erg cm(-2) (3 TeV-2.8 PeV) assuming an E(-2) flux.

  • 92.
    Bringmann, Torsten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Particle Models and the Small-Scale Structure of Dark Matter2009Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, s. 105027-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetic decoupling of weakly interacting massive particles (WIMPs) in the early universe sets a scale that can directly be translated into a small-scale cutoff in the spectrum of matter density fluctuations. The formalism presented here allows a precise description of the decoupling process and thus the determination of this scale to a high accuracy from the details of the underlying WIMP microphysics. With decoupling temperatures of several MeV to a few GeV, the smallest protohalos to be formed range between 10^{-11} and almost 10^{-3} solar masses -- a somewhat smaller range than what was found earlier using order-of-magnitude estimates for the decoupling temperature; for a given WIMP model, the actual cutoff mass is typically about a factor of 10 greater than derived in that way, though in some cases the difference may be as large as a factor of several 100. Observational consequences and prospects to probe this small-scale cutoff, which would provide a fascinating new window into the particle nature of dark matter, are discussed.

  • 93.
    Bringmann, Torsten
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Doro, Michele
    Padova Univ.
    Fornasa, Mattia
    IAP, Paris.
    Dark Matter signals from Draco and Willman 1: Prospects for MAGIC II and CTA2009Inngår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, Vol. 01, nr 016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The next generation of ground-based Imaging Air Cherenkov Telescopes (IACTs) will play an important role in indirect dark matter searches. In this article, we consider two particularly promising candidate sources for dark matter annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study the prospects of detecting such a signal for the soon-operating MAGIC II telescope system as well as for the planned installation of CTA, taking special care of describing the experimental features that affect the detectional prospects. For the first time in such a study, we fully take into account the effect of internal bremsstrahlung, which has recently been shown to considerably enhance, in some cases, the gamma-ray flux at the high energies where Atmospheric Cherenkov Telescopes operate, thus leading to significantly harder annihilation spectra than traditionally considered. While the detection of the spectral features introduced by internal bremsstrahlung would constitute a smoking gun signature for dark matter annihilation, we find that for most models the overall flux still remains at a level that will be challenging to detect unless one adopts rather (though by no means overly) optimistic astrophysical assumptions about the distribution of dark matter in the dwarfs

  • 94.
    Bringmann, Torsten
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lavalle, Julien
    Turin University.
    Salati, Pierre
    Annecy.
    Intermediate Mass Black Holes and Nearby Dark Matter Point Sources: A Myth-Buster2009Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, s. 161301-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The proposal of a galactic population of intermediate mass black holes (IMBHs), forming dark matter (DM) ``mini-spikes'' around them, has received considerable attention in recent years. In fact, leading in some scenarios to large annihilation fluxes in gamma rays, neutrinos and charged cosmic rays, these objects are sometimes quoted as one of the most promising targets for indirect DM searches. In this letter, we apply a detailed statistical analysis to point out that the existing EGRET data already place very stringent limits on those scenarios, making it rather unlikely that any of these objects will be observed with, e.g., the Fermi/GLAST satellite or upcoming Air Cherenkov telescopes. We also demonstrate that prospects for observing signals in neutrinos or charged cosmic rays seem even worse. Finally, we address the question of whether the excess in the cosmic ray positron/electron flux recently reported by PAMELA/ATIC could be due to a nearby DM point source like a DM clump or mini-spike; gamma-ray bounds, as well as the recently released Fermi cosmic ray electron and positron data, again exclude such a possibility for conventional DM candidates, and strongly constrain it for DM purely annihilating into light leptons.

  • 95.
    Burgess, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    A Search for Solar Neutralino Dark Matter with the AMANDA-II Neutrino Telescope2008Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    A relic density of Weakly Interacting Massive Particles (WIMPs) remaining from the Big Bang constitutes a promising solution to the Dark Matter problem. It is possible for such WIMPs to be trapped by and accumulate in gravitational potentials of massive dense objects such as the Sun. A perfect WIMP candidate appears in certain supersymmetric extensions to the Standard Model of particle physics, where the lightest supersymmetric particle is a neutralino which can be stable, massive and weakly interacting. The neutralinos may annihilate pair-wise and in these interactions neutrinos with energies ranging up to the neutralino mass can be indirectly produced. Hence, a possible population of dark matter neutralinos trapped in the Sun can give rise to an observable neutrino flux.

    The Antarctic Muon And Neutrino Detector Array, AMANDA, is a neutrino telescope that detects Cherenkov light emitted by charged particles created in neutrino interactions in the South Pole glacial ice sheet using an array of light detectors frozen into the deep ice. In this work data taken with the AMANDA-II detector during 2003 are analyzed to measure or put upper bounds on the flux of such neutrinos from the Sun. In the analysis detailed signal and background simulations are compared to measurements. Background rejection filters optimized for various neutralino models have been constructed. No excess above the background expected from neutrinos and muons created in cosmic ray interactions in the atmosphere was found. Instead 90% confidence upper limits have been set on the neutralino annihilation rate in the Sun and the muon flux induced by neutralino signal neutrinos.

  • 96.
    Carney, Rebecca
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Instrumentation for silicon tracking at the HL-LHC2017Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    In 2027 the Large Hadron Collider (LHC) at CERN will enter a high luminosity phase, deliver- ing 3000 fb 1 over the course of ten years. The High Luminosity LHC (HL-LHC) will increase the instantaneous luminosity delivered by a factor of 5 compared to the current operation pe- riod. This will impose significant technical challenges on all aspects of the ATLAS detector but particularly the Inner Detector, trigger, and data acquisition systems. In addition, many of the components of the Inner Detector are reaching the end of their designed lifetime and will need to be exchanged. As such, the Inner Detector will be entirely replaced by an all silicon tracker, known as the Inner Tracker (ITk).

    The layout of the Pixel and strip detectors will be optimised for the upgrade and will extend their forward coverage. To reduce the per-pixel hit rate and explore novel techniques for deal- ing with the conditions in HL-LHC, an inter-experiment collaboration called RD53 has been formed. RD53 is tasked with producing a front-end readout chip to be used as part of hybrid Pixel detectors that can deal with the high multiplicity environment in the HL-LHC.

    A silicon sensor, which makes up the other half of the hybrid Pixel detector, must also be designed to cope with the high fluences in HL-LHC. Significant damage will be caused by non- ionising energy loss in the sensor over its lifetime. This damage must be incorporated into the detector simulation both to predict the detector performance at specific conditions and to understand the e↵ects of radiation damage on data taking. The implementation of radiation damage in the ATLAS simulation framework is discussed in this thesis.

    Collisions produced by the HL-LHC also presents a challenge for the current track reconstruc- tion software. High luminosity is obtained, in part, by increasing the number of interactions per bunch crossing, which in turn increases the time taken for track reconstruction. Various ap- proaches to circumvent the strain on projected resources are being explored, including porting existing algorithms to parallel architectures. A popular algorithm used in track reconstruction, the Kalman filter, has been implemented in a neuromorphic architecture: IBM’s TrueNorth. The limits of using such an architecture for tracking, as well as how its performance compares to a non-spiking Kalman filter implementation, are explored in this thesis. 

  • 97.
    Carney, Rebecca
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Lawrence Berkeley National Lab.
    Silicon Tracking and a Search for Long-lived Particles2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The ATLAS Detector, below the surface of the Swiss-French border, measures the remnants of high-energy proton-proton collisions, accelerated by the Large Hadron Collider (LHC) at CERN. Recently the LHC paused operations, having delivered an integrated luminosity corresponding to 150 fb−1 of data at a centre-of-mass energy of 13 TeV. This thesis describes a search for physics beyond the Standard Model using that dataset as well as the charged particle tracking detector technology that renders it possible. The analysis searches for long-lived, massive particles identified by a characteristic decay displaced from the interaction point and produced in association with high momentum jets.

    Searching for rare processes requires sifting through a large amount of data, which stresses the ATLAS computing infrastructure. As such, measures are taken to reduce unnecessary computations and supplement our existing resources with, for example, inherently parallel computing architectures. Early adoption of these new architectures is necessary to understand the feasibility of their potential integration, including porting existing algorithms. A popular algorithm used in track reconstruction, the Kalman filter, has been implemented in a neuromorphic architecture: IBM’s TrueNorth. The limits of using such an architecture for tracking, as well as how its performance compares to a non-spiking Kalman filter implementation, are explored in this thesis.

    In 2026 the LHC will enter a High Luminosity phase (HL-LHC), increasing the instantaneous luminosity by a factor of five and delivering 4000 fb-1 within twelve years. This will impose significant technical challenges on all aspects of the ATLAS detector, resulting in the entire ATLAS Inner Detector being replaced by an all-silicon tracker. ITk (the new “Inner TracKer”) will be comprised of Strip and Pixel detectors. The layout of the Pixel and Strip detectors was optimised for the upgrade to extend their forward coverage. To cope with the increased number of hits per chip per event and explore novel techniques for dealing with the conditions in HL-LHC, an inter-experiment collaboration, RD53, was formed, tasked with producing a front-end readout chip used in Pixel detectors. This thesis will briefly outline the author’s contribution to both of these projects.

    ITk silicon sensors will undergo significant damage over their lifetime due to non-ionising energy loss (NIEL). This damage must be incorporated into the detector simulation both to predict the detector performance and to understand the effects of radiation damage on data taking. The implementation of NIEL radiation damage in the ATLAS simulation framework is discussed in this thesis.

  • 98.
    Carney, Rebecca
    et al.
    Lawrence Berkeley National Laboratory, USA.
    Bouchard, Kris
    Calafiura, Paolo
    Clark, David
    Donofrio, David
    Garcia-Sciveres, Maurice
    Livezey, Jesse
    Neuromorphic Kalman filter implementation in IBM's TrueNorth2017Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 898, nr 4, artikkel-id 042021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Following the advent of a post-Moore’s law field of computation, novel architectures continue to emerge. With composite, multi-million connection neuromorphic chips like IBM’s TrueNorth, neural engineering has now become a feasible technology in this novel computing paradigm. High Energy Physics experiments are continuously exploring new methods of computation and data handling, including neuromorphic, to support the growing challenges of the field and be prepared for future commodity computing trends. This work details the first instance of a Kalman filter implementation in IBM’s neuromorphic architecture, TrueNorth, for both parallel and serial spike trains. The implementation is tested on multiple simulated systems and its performance is evaluated with respect to an equivalent non-spiking Kalman filter. The limits of the implementation are explored whilst varying the size of weight and threshold registers, the number of spikes used to encode a state, size of neuron block for spatial encoding, and neuron potential reset schemes.

  • 99.
    Carney, Rebecca
    et al.
    Lawrence Berkeley National Lab, USA.
    Dunne, Katherine
    Garcia-Sciveres, Mauricio
    Gnani, Dario
    Heim, Timon
    Hemperek, Tomasz
    Krueger, Hans
    Mekkaoui, Abderrazak
    Wallangen, Veronica
    Results of FE65-P2 Pixel Readout Test Chip for High Luminosity LHC Upgrades2017Inngår i: PoS - Proceedings of Science, ISSN 1824-8039, E-ISSN 1824-8039, Vol. 282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A pixel readout test chip called FE65-P2 has been fabricated on 65 nm CMOS technology. FE65-P2 contains a matrix of 64 x 64 pixels on 50 micron by 50 micron pitch, designed to read out a bump bonded sensor. The goals of FE65-P2 are to demonstrate excellent analog performance isolated from digital activity well enough to achieve 500 electron stable threshold, be radiation hard to at least 500 Mrad, and prove the novel concept of isolated analog front ends embedded in a flat digital design, dubbed “analog islands in a digital sea”. Experience from FE65-P2 and hybrid assemblies will be applied to the design for a large format readout chip, called RD53A, to be produced in a wafer run in early 2017 by the RD53 collaboration. We review the case for 65 nm technology and report on threshold stability test results for the FE65-P2.

  • 100. Chaudhuri, A
    et al.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Jones, R G
    Lee, T-L
    Detlefs, B
    Woodruff, D P
    The structure of the Au(111)/methylthiolate interface: new insights from near-edge x-ray absorption spectroscopy and x-ray standing waves.2009Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, nr 12, s. 124708-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The local structure of the Au(111)(√3x√3)R30 degrees-methylthiolate surface phase has been investigated by S K-edge near-edge s-ray absorption fine structure (NEXAFS) both experimentally and theoretically and by experimental normal-incidence x-ray standing waves (NIXSW) at both the C and S atomic sites. NEXAFS shows not only excitation into the intramolecular σ*S-C resonance but also into a σ* S-Au orbital perpendicular to the surface, clearly identifying the local S headgroup site as atop a Au atom. Simulations show that it is not possible, however, to distinguish between the two possible adatom reconstruction models; a single thiolate species atop a hollow-site Au adatom or a dithiolate moiety comprising two thiolate species bonded to a bridge-bonded Au adatom. Within this dithiolate moiety a second σ* S-Au orbital that lies near parallel to the surface has a higher energy that overlaps that of the σ* S-C resonance. The new NIXSW data show the S-C bond to be tilted by 61 degrees relative to the surface normal, with a preferred azimuthal orientation in <211>, corresponding to the intermolecular nearest-neighbor directions. This azimuthal orientation is consistent with the thiolate being atop a hollow-site Au adatom, but not consistent with the originally proposed Au-adatom-dithiolate moiety. However, internal conformational changes within this species could, perhaps, render this model also consistent with the experimental data.

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