154 research outputs found
Detection of Atmospheric Muon Neutrinos with the IceCube 9-String Detector
The IceCube neutrino detector is a cubic kilometer TeV to PeV neutrino
detector under construction at the geographic South Pole. The dominant
population of neutrinos detected in IceCube is due to meson decay in cosmic-ray
air showers. These atmospheric neutrinos are relatively well-understood and
serve as a calibration and verification tool for the new detector. In 2006, the
detector was approximately 10% completed, and we report on data acquired from
the detector in this configuration. We observe an atmospheric neutrino signal
consistent with expectations, demonstrating that the IceCube detector is
capable of identifying neutrino events. In the first 137.4 days of livetime,
234 neutrino candidates were selected with an expectation of 211 +/-
76.1(syst.) +/- 14.5(stat.) events from atmospheric neutrinos
Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of December 27th, 2004 with the AMANDA-II detector
On December 27th 2004, a giant gamma flare from the Soft Gamma-ray Repeater
1806-20 saturated many satellite gamma-ray detectors. This event was by more
than two orders of magnitude the brightest cosmic transient ever observed. If
the gamma emission extends up to TeV energies with a hard power law energy
spectrum, photo-produced muons could be observed in surface and underground
arrays. Moreover, high-energy neutrinos could have been produced during the SGR
giant flare if there were substantial baryonic outflow from the magnetar. These
high-energy neutrinos would have also produced muons in an underground array.
AMANDA-II was used to search for downgoing muons indicative of high-energy
gammas and/or neutrinos. The data revealed no significant signal. The upper
limit on the gamma flux at 90% CL is dN/dE < 0.05 (0.5) TeV^-1 m^-2 s^-1 for
gamma=-1.47 (-2). Similarly, we set limits on the normalization constant of the
high-energy neutrino emission of 0.4 (6.1) TeV^-1 m^-2 s^-1 for gamma=-1.47
(-2).Comment: 14 pages, 3 figure
Calibration and Characterization of the IceCube Photomultiplier Tube
Over 5,000 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-inch 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.Comment: 40 pages, 12 figure
Detecting a stochastic gravitational wave background with the Laser Interferometer Space Antenna
The random superposition of many weak sources will produce a stochastic
background of gravitational waves that may dominate the response of the LISA
(Laser Interferometer Space Antenna) gravitational wave observatory. Unless
something can be done to distinguish between a stochastic background and
detector noise, the two will combine to form an effective noise floor for the
detector. Two methods have been proposed to solve this problem. The first is to
cross-correlate the output of two independent interferometers. The second is an
ingenious scheme for monitoring the instrument noise by operating LISA as a
Sagnac interferometer. Here we derive the optimal orbital alignment for
cross-correlating a pair of LISA detectors, and provide the first analytic
derivation of the Sagnac sensitivity curve.Comment: 9 pages, 11 figures. Significant changes to the noise estimate
Dynamic sea level changes following changes in the thermohaline circulation
Using the coupled climate model CLIMBER-3a, we investigate changes in sea
surface elevation due to a weakening of the thermohaline circulation (THC). In
addition to a global sea level rise due to a warming of the deep sea, this
leads to a regional dynamic sea level change which follows
quasi-instantaneously any change in the ocean circulation. We show that the
magnitude of this dynamic effect can locally reach up to ~1m, depending on the
initial THC strength. In some regions the rate of change can be up to 20-25
mm/yr. The emerging patterns are discussed with respect to the oceanic
circulation changes. Most prominent is a south-north gradient reflecting the
changes in geostrophic surface currents. Our results suggest that an analysis
of observed sea level change patterns could be useful for monitoring the THC
strength.Comment: Climate Dynamics (2004), submitted. See also
http://www.pik-potsdam.de/~ander
The ICECUBE prototype string in AMANDA
The Antarctic Muon And Neutrino Detector Array (Amanda) is a high-energy
neutrino telescope. It is a lattice of optical modules (OM) installed in the
clear ice below the South Pole Station. Each OM contains a photomultiplier tube
(PMT) that detects photons of Cherenkov light generated in the ice by muons and
electrons. IceCube is a cubic-kilometer-sized expansion of Amanda currently
being built at the South Pole. In IceCube the PMT signals are digitized already
in the optical modules and transmitted to the surface. A prototype string of 41
OMs equipped with this new all-digital technology was deployed in the Amanda
array in the year 2000. In this paper we describe the technology and
demonstrate that this string serves as a proof of concept for the IceCube
array. Our investigations show that the OM timing accuracy is 5 ns. Atmospheric
muons are detected in excellent agreement with expectations with respect to
both angular distribution and absolute rate
First year performance of the IceCube neutrino telescope
The first sensors of the IceCube neutrino observatory were deployed at the South Pole during the austral summer of 2004-2005 and have been producing data since February 2005. One string of 60 sensors buried in the ice and a surface array of eight ice Cherenkov tanks took data until December 2005 when deployment of the next set of strings and tanks began. We have analyzed these data, demonstrating that the performance of the system meets or exceeds design requirements. Times are determined across the whole array to a relative precision of better than 3 ns, allowing reconstruction of muon tracks and light bursts in the ice, of air-showers in the surface array and of events seen in coincidence by surface and deep-ice detectors separated by up to 2.5 km
Limits to the muon flux from neutralino annihilations in the Sun with the AMANDA detector
A search for an excess of muon-neutrinos from neutralino annihilations in the
Sun has been performed with the AMANDA-II neutrino detector using data
collected in 143.7 days of live-time in 2001. No excess over the expected
atmospheric neutrino background has been observed. An upper limit at 90%
confidence level has been obtained 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 100 GeV-5000 GeV.Comment: 13 pages, 3 figures. Submitted to Astropart. Phy
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