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Sökning: WFRF:(Zarzhitsky P.) > Berdermann J.

  • Resultat 1-10 av 43
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1.
  • Abbasi, R., et al. (författare)
  • Calibration and characterization of the IceCube photomultiplier tube
  • 2010
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. - 0168-9002. ; 618:1-3, s. 139-152
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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2.
  • Abbasi, R., et al. (författare)
  • Constraints on high-energy neutrino emission from SN 2008D
  • 2011
  • Ingår i: Astronomy and Astrophysics. - 0004-6361. ; 527:4, s. A28
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 similar to 100 events for a core-collapse supernova at 10 Mpc according to the soft jet model.
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3.
  • Abbasi, R., et al. (författare)
  • Constraints on the extremely-high energy cosmic neutrino flux with the IceCube 2008-2009 data
  • 2011
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:9, s. 092003
  • Tidskriftsartikel (refereegranskat)abstract
    • 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).
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4.
  • Abbasi, R., et al. (författare)
  • First search for atmospheric and extraterrestrial neutrino-induced cascades with the IceCube detector
  • 2011
  • Ingår i: Physical Review D. - 1550-7998. ; 84:7, s. 072001
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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5.
  • Abbasi, R., et al. (författare)
  • First search for extremely high energy cosmogenic neutrinos with the IceCube Neutrino Observatory
  • 2010
  • Ingår i: Physical review. D, Particles, fields, gravitation, and cosmology. - 1550-7998. ; 82:7, s. 072003
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the results of the search for extremely-high energy neutrinos with energies above 10(7) GeV obtained with the partially (similar to 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 E-2 phi(ve+v mu+v tau) similar or equal to 1.4 x 10(-6) GeV cm(-2) sec(-1) sr(-1) for neutrinos in the energy range from 3 x 10(7) to 3 x 10(9) GeV.
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6.
  • Abbasi, R., et al. (författare)
  • Limits on Neutrino Emission from Gamma-Ray Bursts with the 40 String IceCube Detector
  • 2011
  • Ingår i: Physical Review Letters. - 0031-9007. ; 106:14, s. 141101
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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7.
  • Abbasi, R., et al. (författare)
  • Measurement of the anisotropy of cosmic-ray arrival directions with icecube
  • 2010
  • Ingår i: The Astrophysical Journal Letters. - 2041-8205. ; 718:2, s. L194-L198
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first observation of an anisotropy in the arrival direction of cosmic rays with energies in the multi-TeV region in the Southern sky using data from the IceCube detector. Between 2007 June and 2008 March, the partially deployed IceCube detector was operated in a configuration with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 m inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic-ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the southern sky. The data include 4.3 billion muons produced by downward-going cosmic-ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of similar to 20 TeV. Their arrival direction distribution exhibits an anisotropy in right ascension with a first-harmonic amplitude of (6.4 +/- 0.2 stat. +/- 0.8 syst.) x 10(-4).
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8.
  • Abbasi, R., et al. (författare)
  • Measurement of the atmospheric neutrino energy spectrum from 100 GeV to 400 TeV with IceCube
  • 2011
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:1, s. 012001
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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9.
  • Abbasi, R., et al. (författare)
  • Neutrino Analysis of the 2010 September Crab Nebula Flare and Time-Integrated Constraints on Neutrino Emission from the Crab Using Icecube
  • 2012
  • Ingår i: Astrophysical Journal. - 0004-637X. ; 745:1, s. 45
  • Tidskriftsartikel (refereegranskat)abstract
    • 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. gamma-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-upsilon(2). 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. gamma-rays. The 90% confidence level (CL) best upper limits on the Crab flux during the 10 day flare are 4.73 x 10(-11) cm(-2) s(-1) TeV-1 for an E-upsilon(2). neutrino spectrum and 2.50 x 10(-10) cm(-2) s(-1) TeV-1 for a softer neutrino spectra of E-upsilon(-2.7), 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.
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10.
  • Abbasi, R., et al. (författare)
  • Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube
  • 2011
  • Ingår i: Astrophysical Journal. - 0004-637X. ; 740:1, s. 16
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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