13 research outputs found
Search for Neutrinos from Annihilating Dark Matter in the Direction of the Galactic Center with the 40-String IceCube Neutrino Observatory
A search for muon neutrinos from dark matter annihilations in the Galactic Center region has been performed with the 40-string configuration of the IceCube Neutrino Observatory using data collected in 367 days of live-time starting in April 2008. The observed fluxes were consistent with the atmospheric background expectations. Upper limits on the self-annihilation cross-section are obtained for dark matter particle masses ranging from 100 GeV to 10 TeV. In the case of decaying dark matter, lower limits on the lifetime have been determined for masses between 200 GeV and 20 TeV
IceTop: The surface component of IceCube
IceTop, the surface component of the IceCube Neutrino Observatory at the South Pole, is an air shower array with an area of 1 km2. The detector allows a detailed exploration of the mass composition of primary cosmic rays in the energy range from about 100 TeV to 1 EeV by exploiting the correlation between the shower energy measured in IceTop and the energy deposited by muons in the deep ice. In this paper we report on the technical design, construction and installation, the trigger and data acquisition systems as well as the software framework for calibration, reconstruction and simulation. Finally the first experience from commissioning and operating the detector and the performance as an air shower detector will be discussed. </p
Use of event-level neutrino telescope data in global fits for theories of new physics
We present a fast likelihood method for including event-level neutrino telescope data in parameter explorations of theories for new physics, and announce its public release as part of DarkSUSY 5.0.6. Our construction includes both angular and spectral information about neutrino events, as well as their total number. We also present a corresponding measure for simple model exclusion, which can be used for single models without reference to the rest of a parameter space. We perform a number of supersymmetric parameter scans with IceCube data to illustrate the utility of the method: example global fits and a signal recovery in the constrained minimal supersymmetric standard model (CMSSM), and a model exclusion exercise in a 7-parameter phenomenological version of the MSSM. The final IceCube detector configuration will probe almost the entire focus-point region of the CMSSM, as well as a number of MSSM-7 models that will not otherwise be accessible to e.g. direct detection. Our method accurately recovers the mock signal, and provides tight constraints on model parameters and derived quantities. We show that the inclusion of spectral information significantly improves the accuracy of the recovery, providing motivation for its use in future IceCube analyses
Lateral distribution of muons in IceCube cosmic ray events
In cosmic ray air showers, the muon lateral separation from the center of the shower is a measure of the transverse momentum that the muon parent acquired in the cosmic ray interaction. IceCube has observed cosmic ray interactions that produce muons laterally separated by up to 400 m from the shower core, a factor of 6 larger distance than previous measurements. These muons originate in high pT (>2ââGeV/c) interactions from the incident cosmic ray, or high-energy secondary interactions. The separation distribution shows a transition to a power law at large values, indicating the presence of a hard pT component that can be described by perturbative quantum chromodynamics. However, the rates and the zenith angle distributions of these events are not well reproduced with the cosmic ray models tested here, even those that include charm interactions. This discrepancy may be explained by a larger fraction of kaons and charmed particles than is currently incorporated in the simulations. </p
Cosmic ray composition and energy spectrum from 1â30 PeV using the 40-string configuration of IceTop and IceCube
The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these particles. At the South Pole, the IceCube Neutrino Observatory is capable of measuring two components of cosmic ray air showers in coincidence: the electromagnetic component at high altitude (2835 m) using the IceTop surface array, and the muonic component above âŒ1 TeV using the IceCube array. This unique detector arrangement provides an opportunity for precision measurements of the cosmic ray energy spectrum and composition in the region of the knee and beyond. We present the results of a neural network analysis technique to study the cosmic ray composition and the energy spectrum from 1 PeV to 30 PeV using data recorded using the 40-string/40-station configuration of the IceCube Neutrino Observatory. </p
Five years of searches for point sources of astrophysical neutrinos with the AMANDA-II neutrino telescope
Multiyear search for a diffuse flux of muon neutrinos with AMANDA-II (vol 76, artn 042008, 2007)
Measurement of sound speed vs. depth in South Pole ice for neutrino astronomy
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
South Pole Station 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 from
50 to 2250 m depth, from which we determined a value for the pressure wave
speed consistent with that determined with the sensors operating at shallower
depths and higher frequencies. These results have encouraging implications for
neutrino astronomy: The negligible refraction of acoustic waves deeper than 200
m indicates that good neutrino direction and energy reconstruction, as well as
separation from background events, could be achieved.Comment: 14 pages, 7 figure
An absence of neutrinos associated with cosmic-ray acceleration in <em>Îł</em>-ray bursts
Very energetic astrophysical events are required to accelerate cosmic rays to above 1018âelectronvolts. GRBs (Îł-ray bursts) have been proposed as possible candidate source1, 2, 3. In the GRB âfireball' model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and Îł-rays. Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux. Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions. This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 10âelectronvolts or that the efficiency of neutrino production is much lower than has been predicte