7 research outputs found
All-particle cosmic ray energy spectrum measured with 26 IceTop stations
We report on a measurement of the cosmic ray energy spectrum with the IceTop
air shower array, the surface component of the IceCube Neutrino Observatory at
the South Pole. The data used in this analysis were taken between June and
October, 2007, with 26 surface stations operational at that time, corresponding
to about one third of the final array. The fiducial area used in this analysis
was 0.122 km^2. The analysis investigated the energy spectrum from 1 to 100 PeV
measured for three different zenith angle ranges between 0{\deg} and 46{\deg}.
Because of the isotropy of cosmic rays in this energy range the spectra from
all zenith angle intervals have to agree. The cosmic-ray energy spectrum was
determined under different assumptions on the primary mass composition. Good
agreement of spectra in the three zenith angle ranges was found for the
assumption of pure proton and a simple two-component model. For zenith angles
{\theta} < 30{\deg}, where the mass dependence is smallest, the knee in the
cosmic ray energy spectrum was observed between 3.5 and 4.32 PeV, depending on
composition assumption. Spectral indices above the knee range from -3.08 to
-3.11 depending on primary mass composition assumption. Moreover, an indication
of a flattening of the spectrum above 22 PeV were observed.Comment: 38 pages, 17 figure
Measurement of Acoustic Attenuation in South Pole Ice
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 alpha =
3.20 \pm 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 lambda = 1/alpha of ~1/300 m with 20% uncertainty. No
significant depth or frequency dependence has been found.Comment: 17 pages, 12 figures, published in Astroparticle Physics, 201
The design and performance of IceCube DeepCore
The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore. © 2012 Elsevier B.V. All rights reserved.0IceCube CollaborationSCOPUS: ar.jinfo:eu-repo/semantics/publishe
Background studies for acoustic neutrino detection at the South Pole
The detection of acoustic signals from ultra-high energy neutrino
interactions is a promising method to measure the tiny 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 to 50 kHz frequency range to be smaller than 20 mPa.
Using a threshold trigger, sensors of the South Pole Acoustic Test Setup
registered acoustic pulse-like events in the IceCube detector volume and its
vicinity. Acoustic signals from refreezing IceCube holes and from anthropogenic
sources have been used to localize acoustic events. Monte Carlo simulations of
sound propagating from the established sources to the SPATS sensors have
allowed to check corresponding model expectations. An upper limit on the
neutrino flux at energies GeV is derived from acoustic data
taken over eight months.Comment: 17 pages, 14 figure
Search for neutrino-induced cascades with five years of AMANDA data
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 Îœe:ΜΌ: ÎœÏ = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Ί â E-2 is less than 5.0 Ă 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. © 2010 Elsevier B.V. All rights reserved.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Multi-messenger Observations of a Binary Neutron Star Merger
International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over âŒ10 days. Following early non-detections, X-ray and radio emission were discovered at the transientâs position and days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta