[en] In order to detect cosmic ray air showers and neutrinos, the software data acquisition (DAQ) system of the IceCube Neutrino Observatory forms triggers on patterns of Cherenkov light deposition in the detector based on temporal and/or spatial coincidences. Here we describe the algorithms used for triggering, as well as the fast merging algorithm used to combine the time-ordered hit streams from the optical modules. We also present recently implemented and planned modifications of the DAQ that take advantage of our newly upgraded multi-core computer systems at the South Pole

[en] Many sensor networks, including large particle detector arrays measuring high-energy cosmic-ray air showers, traditionally rely on centralised trigger algorithms to find spatial and temporal coincidences of individual nodes. Such schemes suffer from scalability problems, especially if the nodes communicate wirelessly or have bandwidth limitations. However, nodes which instead communicate with each other can, in principle, use a distributed algorithm to find coincident events themselves without communication with a central node. We present such an algorithm and consider various design tradeoffs involved, in the context of a potential trigger for the Auger Engineering Radio Array (AERA).

[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 ν_μ+ν_μ flux.

[en] We report on a search for extremely-high energy neutrinos with energies greater than 10⁶ 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 2.0x10⁶-6.3x10⁹ GeV to a level of E²φ≤3.6x10^-8 GeV cm^-2 sec^-1 sr^-1.

[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 <σ_Av>≅10^-22 cm³ s^-1 for weakly interacting massive particle masses above 1 TeV, assuming a monochromatic neutrino line spectrum.

[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 E²Φ_90%CL<3.6x10^-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 Φ∝E^-2 and the flavor composition of the ν_e ratio ν_μ ratio ν_τ flux is 1 ratio 1 ratio 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.

[en] We present here a comparison of interaction models commonly used for simulating cosmic ray shower development in the atmosphere at energies greater than 1 TeV. The implementations of these models in CORSIKA and the FLUKA transport and interaction code are relevant for extensive air shower experiments, neutrino telescopes, and gamma-ray surfacebased detectors. We compare the pion, kaon, charmed meson and baryon energy fractions and the multiplicities at the first interaction stage of monoenergetic protons on nitrogen nuclei in the range 1 TeV-100 PeV. We also show comparisons in terms of Z-moments, a spectrumweighted multiplicity often used in the cosmic ray community. The transverse and longitudinal momentum distributions of the secondary muons produced in proton-nitrogen collisions are also shown