University of Wisconsin-Madison

IceCube Contributions to ICRC 2009

Complete version of all papers (PDF ∼ 15 MB)

Table of Contents (PDF ∼ 147 KB) — Author List

    • 1339: IceCube
    • Albrecht Karle, for the IceCube Collaboration (Highlight paper)
    • Abstract: IceCube is a 1 km3 neutrino telescope currently under construction at the South Pole. The detector will consist of 5160 optical sensors deployed at depths between 1450 m and 2450 m in clear Antarctic ice evenly distributed over 86 strings. An air shower array covering a surface area of 1 km2 above the in-ice detector will measure cosmic ray air showers in the energy range from 300 TeV to above 1 EeV. The detector is designed to detect neutrinos of all flavors: νe, νμ and ντ. With 59 strings currently in operation, construction is 67% complete. Based on data taken to date, the observatory meets its design goals. Selected results will be presented.
    • 0653: All-Sky Point-Source Search with 40 Strings of IceCube
    • Jon Dumm, Juan A. Aguilar, Mike Baker, Chad Finley, Teresa Montaruli, for the IceCube Collaboration
    • Abstract: During 2008-09, the IceCube Neutrino Observatory was operational with 40 strings of optical modules deployed in the ice. We describe the search for neutrino point sources based on a maximum likelihood analysis of the data collected in this configuration. This data sample provides the best sensitivity to high energy neutrino point sources to date. The field of view is extended into the down-going region providing sensitivity over the entire sky. The 22-string result is discussed, along with improvements leading to updated angular resolution, effective area, and sensitivity. The improvement in the performance as the number of strings is increased is also shown.
    • 0812: IceCube Time-Dependent Point Source Analysis Using Multiwavelength Information
    • M. Baker, J. A. Aguilar, J. Braun, J. Dumm, C. Finley, T. Montaruli, S. Odrowski, E. Resconi for the IceCube Collaboration
    • Abstract: In order to enhance the IceCube's sensitivity to astrophysical objects, we have developed a dedicated search for neutrinos in coincidence with flares detected in various photon wavebands from blazars and high-energy binary systems. The analysis is based on a maximum likelihood method including the reconstructed position, the estimated energy and arrival time of IceCube events. After a short summary of the phenomenological arguments motivating this approach, we present results from data collected with 22 IceCube strings in 2007-2008. First results for the 40-string IceCube configuration during 2008-2009 will be presented at the conference. We also report on plans to use long light curves and extract from them a time variable probability density function.
    • 0960: Search for neutrino flares from point sources with IceCube (0908.4209)
    • J. L. Bazo Alba, E. Bernardini, R. Lauer, for the IceCube Collaboration
    • Abstract: A time-dependent search for neutrino flares from pre-defined directions in the whole sky is presented. The analysis uses a time clustering algorithm combined with an unbinned likelihood method. This algorithm provides a search for significant neutrino flares over time-scales that are not fixed a-priori and that are not triggered by multiwavelength observations. The event selection is optimized to maximize the discovery potential, taking into account different time-scales of source activity and background rates. Results for the 22-string IceCube data from a pre-defined list of bright and variable astrophysical sources will be reported at the conference.
    • 0987: Neutrino triggered high-energy gamma-ray follow-up with IceCube
    • Robert Franke, Elisa Bernardini for the IceCube collaboration
    • Abstract: We present the status of a program for the generation of online alerts issued by IceCube for gamma-ray follow up observations by Air Cherenkov telescopes (e.g. MAGIC). To overcome the low probability of simultaneous observations of flares of objects with gamma-ray and neutrino telescopes a neutrino-triggered follow-up scheme is developed. This mode of operation aims at increasing the availability of simultaneous multi-messenger data which can increase the discovery potential and constrain the phenomenological interpretation of the high energy emission of selected source classes (e.g. blazars). This requires a fast and stable online analysis of potential neutrino signals. We present the work on a significance-based alert scheme for a list of phenomenologically selected sources. To minimize the rate of false alerts due to detector instabilities a fast online monitoring scheme based on IceCube trigger and filter rates was implemented.
    • 1173: Moon Shadow Observation by IceCube
    • D.J. Boersma, L. Gladstone and A. Karle for the IceCube Collaboration
    • Abstract: In the absence of an astrophysical standard candle, IceCube can study the deficit of cosmic rays from the direction of the Moon. The observation of this “Moon shadow” in the downgoing muon flux is an experimental verification of the absolute pointing accuracy and the angular resolution of the detector with respect to energetic muons passing through. The Moon shadow has been observed in the 40-string configuration of IceCube. This is the first stage of IceCube in which a Moon shadow analysis has been successful. Method, results, and some systematic error studies will be discussed.
    • 1289: IceCube/AMANDA combined analyses for the search of neutrino sources at low energies
    • Cécile Roucelle, Andreas Gross, Sirin Odrowski, Elisa Resconi, Yolanda Sestayo
    • Abstract: During the construction of IceCube, the AMANDA neutrino telescope has continued to acquire data and has been surrounded by IceCube strings. Since the year 2007, AMANDA has been fully integrated for data acquisition and joint IceCube/AMANDA events have been recorded. Because of the finer spacing of AMANDA phototubes, the inclusion of AMANDA significantly extends the detection capability of IceCube alone for low energy neutrinos (100 GeV to 10 TeV). We present the results of two analyses performed on the 2007-2008 Icecube (22 string) and AMANDA data. No evidence of high energy neutrino emission was observed; upper limits are reported.In 2008-09, IceCube acquired data in a 40 string configuration together with the last year of operation of AMANDA. Progress on the analysis of this new combined IceCube/AMANDA sample are presented as well. In addition, a novel method to study an extended region surrounding the most active parts of Cygnus with these datasets is described here.
    • 1127: AMANDA 7-Year Multipole Analysis (0906.3942)
    • Anne Schukraft, Jan-Patrick Hülß for the IceCube Collaboration
    • Abstract: The multipole analysis investigates the arrival directions of registered neutrino events in AMANDA-II by a spherical harmonics expansion. The expansion of the expected atmospheric neutrino distribution returns a characteristic set of expansion coefficients. This characteristic spectrum of expansion coefficients can be compared with the expansion coefficients of the experimental data. As atmospheric neutrinos are the dominant background of the search for extraterrestrial neutrinos, the agreement of experimental data and the atmospheric prediction can give evidence for physical neutrino sources or systematic uncertainties of the detector. Astrophysical neutrino signals were simulated and it was shown that they influence the expansion coefficients in a characteristic way. Those simulations are used to analyze deviations between experimental data and Monte Carlo simulations with regard to potential physical reasons. The analysis method was applied on the AMANDA-II neutrino sample measured between 2000 and 2006 and results are presented.
    • 1418: Measurement of the atmospheric neutrino energy spectrum with IceCube
    • Dmitry Chirkin for the IceCube collaboration
    • Abstract: The IceCube detector, as configured during its operation in 2007, consisted of 22 deployed cables, each equipped with 60 optical sensors, has been the biggest neutrino detector operating during the year 2007, superseded only by its later configurations. A high quality sample of more than 8500 atmospheric neutrinos was extracted from this single year of operation and used for the measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 500 TeV discussed here. Several statistical techniques were used in an attempt to search for deviation of the neutrino flux from that of conventional atmospheric neutrino models.
    • 0785: Atmospheric Neutrino Oscillation Measurements with IceCube
    • Carsten Rott for the IceCube Collaboration
    • Abstract: IceCube's lowest energy threshold for the detection of track like events (muon neutrinos) is realized in vertical events, due to IceCube's geometry. For this specific class of events, IceCube may be able to observe muon neutrinos with energies below 100 GeV at a statistically significant rate. For these vertically up-going atmospheric neutrinos, which travel a baseline length of the diameter of the Earth, oscillation effects are expected to become significant. We discuss the prospects of observing atmospheric neutrino oscillations and sensitivity to oscillation parameters based on a muon neutrino disappearance measurement performed on IceCube data with vertically up-going track-like events. We further discuss future prospects of this measurement and the impact of an IceCube string trigger configuration that has been active since 2008 and was specifically designed for the detection of these events.
    • 1565: Direct Measurement of the Atmospheric Muon Energy Spectrum with IceCube (0909.0679)
    • Patrick Berghaus for the IceCube Collaboration
    • Abstract: Data from the IceCube detector in its 22-string configuration (IC22) were used to directly measure the atmospheric energy spectrum near the horizon. After passage through more than 10 km of ice, muon bundles from air showers are reduced to single muons, whose energy can be estimated from the total number of photons registered in the detector. The energy distribution obtained in this way is sensitive to the cosmic ray composition around the knee and is complementary to measurements by air shower arrays. The method described extends the physics potential of neutrino telescopes and can easily be applied in similar detectors. Presented is the result from the analysis of one month of IC22 data. The entire event sample will be unblinded once systematic detector effects are fully understood.
    • 1400: Search for Diffuse High Energy Neutrinos with IceCube
    • Kotoyo Hoshina for the IceCube collaboration
    • Abstract: We performed a search for diffuse high energy neutrinos using data obtained with the IceCube 22 string detector during a period 2007-2008. In this analysis we used an E−2 spectrum as a typical flux resulting from cosmic ray shock acceleration. Using a likelihood track reconstruction, approximately 5700 track-like neutrinos are extracted from 275.7 days data at an estimated 95% purity level. The expected sensitivities obtained are in a range of 2.2×10−8∼ 2.6×10−8 E−2 GeV cm−2 s−1 sr−1 with four different energy estimators. The analysis method and results are presented along with discussions of systematics.
    • 1311: A Search For Atmospheric Neutrino-Induced Cascades with IceCube (0910.0215)
    • Michelangelo D'Agostino for the IceCube Collaboration
    • Abstract: The IceCube detector is an all-flavor neutrino telescope. For several years IceCube has been detecting muon tracks from charged-current muon neutrino interactions in ice. However, IceCube has yet to observe the electromagnetic or hadronic particle showers or “cascades” initiated by charged- or neutral-current neutrino interactions. The first detection of such an event signature will likely come from the known flux of atmospheric electron and muon neutrinos. A search for atmospheric neutrino-induced cascades was performed using a full year of IceCube data. Reconstruction and background rejection techniques were developed to reach, for the first time, an expected signal-to-background ratio ∼1 or better.
    • 0882: First search for extraterrestrial neutrino-induced cascades with IceCube (0909.0989)
    • Joanna Kiryluk for the IceCube Collaboration
    • Abstract: We report on the first search for extra-terrestrial neutrino-induced cascades in IceCube. The analyzed data were collected in the year 2007 when 22 detector strings were installed and operated. We will discuss the analysis methods used to reconstruct cascades and to suppress backgrounds. Simulated neutrino signal events with a E-2 energy spectrum, which pass the background rejection criteria, are reconstructed with a resolution ∆(log E) ∼ 0.27 in the energy range from ∼ 20 TeV to a few PeV. We present the range of the diffuse flux of extra-terrestrial neutrinos in the cascade channel in IceCube within which we expect to be able to put a limit.
    • 0708: Improved Reconstruction of Cascade-like Events in IceCube
    • Eike Middell, Joseph McCartin and Michelangelo D'Agostino for the IceCube Collaboration
    • Abstract: Cascade-like events are one of the main signatures in the IceCube neutrino detector. This signature includes electromagnetic and hadronic particle showers from charged or neutral current interactions and hence it provides sensitivity to all neutrino flavours. At energies below 10 PeV these cascades have characteristic lengths of only several meters. Compared to the dimensions of the detector they appear as point-like but anisotropic light sources. We present a new approach to the reconstruction of such events. A maximum likelihood algorithm that incorporates the results of detailed simulations of the light propagation in ice, allows for a significantly better analysis of the recorded photon intensities and arrival times. The performance of the algorithm is evaluated in a Monte Carlo study. It suggests that for cascades an angular resolution of 30° is possible.
    • 1221: Searches for neutrinos from GRBs with the IceCube 22-string detector and sensitivity estimates for the full detector
    • A. Kappes, P. Roth, E. Strahler, for the IceCube Collaboration
    • Abstract: This contribution presents results of searches with IceCube in its 22-string configuration for neutrinos from 41 stacked gamma-ray bursts (GRBs) detected in the northern sky by satellites like Swift. In addition, the capabilities of the full 80-string detector based on a detailed simulation are discussed. GRBs are among the few potential source classes for the highest energy cosmic rays and one of the most puzzling phenomena in the universe. In their ultra-relativistic jets, GRBs are thought to produce neutrinos with energies well in excess of 100 TeV. However, up to now, no such neutrino has been observed. IceCube, currently under construction at the South Pole, is the first km3 scale neutrino telescope. As such it will have a significantly improved sensitivity compared to the precursor class of 0.01 km3 neutrino telescopes.
    • 0515: Search for neutrinos from GRBs with IceCube
    • K. Meagher, P. Roth, I. Taboada, K. Hoffman, for the IceCube Collaboration
    • Abstract: Gamma-ray bursts (GRBs) are one of the few potential sources for the highest energy cosmic rays and one of the most puzzling phenomena in the universe. In their ultra relativistic jets, GRBs are thought to produce neutrinos with energies well in excess of 100 TeV. IceCube, a neutrino telescope currently under construction at the South Pole, will have improved sensitivity to these yet unobserved neutrinos. This contribution describes the methods used for all IceCube neutrino searches from GRBs triggered by satellites. We also present the status of three searches for neutrinos in coincidence with GRBs. The first search seeks to extend existing IceCube 22-string νμ searches to the high background southern hemisphere bursts. A second search looks for neutrino-induced cascades with the 22-string configuration of IceCube. Another νμ search is planned for the 40-string configuration of IceCube, and its status is presented here. This paper is a companion of another ICRC IceCube contribution that summarizes the IceCube 22-string northern hemisphere νμ GRB search results and the expected capabilities of the completed 86-string detector.
    • 0393: Search for GRB neutrinos via a (stacked) time profile analysis
    • Martijn Duvoort and Nick van Eijndhoven for the IceCube collaboration
    • Abstract: An innovative method to detect high-energy neutrinos from Gamma Ray Bursts (GRBs) is presented. The procedure provides a good sensitivity for both prompt, precursor and afterglow neutrinos within a 2 hour time window around the GRB trigger time. The basic idea of the method consists of stacking of the observed neutrino arrival times with respect to the corresponding GRB triggers. A possible GRB neutrino signal would manifest itself as a clustering of signal candidate events in the observed time profile. The stacking procedure allows to identify a signal even in the case of very low rates. We outline the expected performance of analysing four years of AMANDA data (2005–2008) for a sample of 130 GRBs. Because of the extreme optical brightness of GRB080319B, it might be that this particular burst yielded multiple detectable neutrinos in our detector. As such, the method has also been applied to the data of this single burst time profile. The results of this analysis are presented in a separate section.
    • 0764: Optical follow-up of high-energy neutrinos detected by IceCube (0909.0631)
    • Anna Franckowiak, Carl Akerlof, D. F. Cowen, Marek Kowalski, Ringo Lehmann, Torsten Schmidt and Fang Yuan for the IceCube Collaboration and for the ROTSE Collaboration
    • Abstract: Three-quarters of the 1 km neutrino telescope IceCube is currently taking data. Current models predict high-energy neutrino emission from transient objects like supernovae (SNe) and gamma-ray bursts (GRBs). To increase the sensitivity to such transient objects we have set up an optical follow-up program that triggers optical observations on multiplets of high-energy muon-neutrinos. We define multiplets as a minimum of two muon-neutrinos from the same direction (within 4° ) that arrive within a 100 s time window. When this happens, an alert is issued to the four ROTSE-III telescopes, which immediately observe the corresponding region in the sky. Image subtraction is applied to the optical data to find transient objects. In addition, neutrino multiplets are investigated online for temporal and directional coincidence with gamma-ray satellite observations issued over the Gamma-Ray Burst Coordinate Network. An overview of the full program is given, from the online selection of neutrino events to the automated follow-up, and the resulting sensitivity to transient neutrino sources is presented for the first time.
    • 0505: Results and Prospects of Indirect Searches for Dark Matter with IceCube
    • Carsten Rott and Gustav Wikström for the IceCube collaboration
    • Abstract: Dark matter could be indirectly detected through the observation of neutrinos produced as part of its self-annihilation process. Possible signatures are an excess neutrino flux from the Sun, the center of the Earth or from the galactic halo, where dark matter could be gravitationally trapped. We present a search for muon neutrinos from neutralino annihilations in the Sun performed on IceCube data collected with the 22-string configuration. No excess over the expected atmospheric background has been observed and upper limits at 90% confidence level have been obtained on the annihilation rate and converted to limits on WIMP-proton cross-sections, for neutralino masses in the range of 250 GeV to 5 TeV. Further prospects for the detection of dark matter from the Sun, the Earth, and the galactic halo will be discussed.
    • 1356: Search for the Kaluza-Klein Dark Matter with the AMANDA/IceCube Detectors (0906.3969)
    • Matthias Danninger and Kahae Han for the IceCube Collaboration
    • Abstract: A viable WIMP candidate, the lightest Kaluza-Klein particle (LKP), is motivated by theories of universal extra dimensions. LKPs can scatter off nuclei in large celestial bodies, like the Sun, and become trapped within their deep gravitational wells, leading to high WIMP densities in the object's core. Pair-wise LKP annihilation could lead to a detectable high energy neutrino flux from the center of the Sun in the IceCube neutrino telescope. We describe an ongoing search for Kaluza-Klein solar WIMPs with the AMANDA-II data for the years 2001-2003, and also present a UED dark matter sensitivity projected to 180 days from a study of data taken with the combined AMANDA II and IceCube detector in the year 2007. A competitive sensitivity, compared to existing direct and indirect search experiments, on the spin-dependent cross section of the LKP on protons is also presented.
    • 0834: Searches for WIMP Dark Matter from the Sun with AMANDA (0906.1615)
    • James Braun and Daan Hubert for the IceCube Collaboration
    • Abstract: A well-known potential dark matter signature is emission of GeV - TeV neutrinos from annihilation of neutralinos gravitationally bound to massive objects. We present results from recent searches for high energy neutrino emission from the Sun with AMANDA, in all cases revealing no significant excess. We show limits on both neutralino-induced muon flux from the Sun and neutralino-nucleon cross section, comparing them with recent IceCube results. Particularly, our limits on spin-dependent cross section are much better than those obtained in direct detection experiments, allowing AMANDA and other neutrino telescopes to search a complementary portion of MSSM parameter space.
    • 0861: The extremely high energy neutrino search with IceCube
    • Keiichi Mase, Aya Ishihara and Shigeru Yoshida for the IceCube Collaboration
    • Abstract: A search for extremely high energy (EHE) cosmogenic neutrinos has been performed with IceCube. An understanding of high-energy atmospheric muon backgrounds that have a large uncertainty is the key for this search. We constructed an empirical high-energy background model. Extensive comparisons of the empirical model with the observational data in the background dominated region were performed, and the empirical model describes the observed atmospheric muon backgrounds properly. We report the results based on the data collected in 2007 with the 22 string configuration of IceCube. Since no event was found after the search for the EHE neutrinos, a preliminary upper limit on an E−2 flux of E2 φνeμτ ≤ 5.6 × 10−7 GeV cm−2 s−1 sr−1 (90% C.L.) is placed in the energy range 107.5 < Eν < 1010.6 GeV.
    • 0913: Study of very bright cosmic-ray induced muon bundle signatures measured by the IceCube detector
    • Aya Ishihara for the IceCube Collaboration
    • Abstract: We present the study of cosmic-ray induced atmospheric muon signatures measured by the underground IceCube array, some of which coincide with signals in the IceTop surface detector array. In this study, cosmic-ray primary energies are associated with the total number of photoelectrons (NPEs) measured by the underground IceCube optical sensors with two methods. We found that multiple muons that produce 104 ∼ 105 NPEs in the IceCube detector in 2008 is corresponding to the cosmic-ray primary energies of 107 ∼ 109 GeV. This association allows us to study cosmic-ray physics using photon distributions observed by the underground detector that are characterized by the properties of muon bundles. It is observed that the detailed NPE space distributions in longitudinal and lateral directions from muon tracks display the ranging-out effect of low energy muons in each muon bundle. The distributions from 2008 high energy muon data samples taken with the IceCube detector are compared with two different Monte Carlo simulations. The first is an extreme case that assumes a single high energy muon in which nearly all of the energy loss is due to stochastic processes in the ice. The other uses the CORSIKA program with SYBILL and QGSJET-II high energy hadron interaction models, in which approximately half of the energy loss is due to ionization of low energy muons.
    • 1198: Search for High Energetic Neutrinos from Supernova Explosions with AMANDA (0907.4621)
    • Dirk Lennarz and Christopher Wiebusch for the IceCube Collaboration
    • Abstract: Supernova explosions are among the most energetic phenomena in the known universe. There are suggestions that cosmic rays up to EeV energies might be accelerated in the young supernova shell on time scales of a few weeks to years, which would lead to TeV neutrino radiation. The data taken with the AMANDA neutrino telescope in the years 2000 to 2006 is analysed with a likelihood approach in order to search for directional and temporal coincidences between neutrino events and optically observed extra-galactic supernovae. The supernovae were stacked in order to enhance the sensitivity. A catalogue of relevant core-collapse supernovae has been created. This poster presents the results from the analysis.
    • 0549: Search for Ultra High Energy Neutrinos with AMANDA
    • Andrea Silvestri for the IceCube Collaboration
    • Abstract: We present results from the search for diffusely distributed Ultra High Energy (UHE) neutrinos performed on data collected in 2003-2005 with the AMANDA experiment. At energies above a few PeV the Earth is opaque to neutrinos, therefore neutrinos must be differentiated from downward going cosmic ray induced (bundles of) muons. A search for a diffuse flux of UHE neutrinos shows no events, leading to a flux limit, summed over all flavors E2 φν ≤ 8.4 × 10−8 GeV cm−2 s−1 sr−1 (90% confidence level) for 1015.2 eV < Eν < 1018.8 eV. This limit is the most stringent placed to date. A number of model predictions different from the E−2 spectrum have been tested and some have been rejected at a 90% C.L. We show that these results can also place a limit on the flux from point sources in the Southern Sky as a function of declination and valid in the same energy range.
    • 1372: Selection of High Energy Tau Neutrinos in IceCube
    • Seon-Hee Seo and P. A. Toale for the IceCube Collaboration
    • Abstract: Astrophysical neutrino sources are expected to produce electron and muon flavor neutrinos via charged pion decay. Over cosmological distances, standard neutrino oscillations will change the flavor content to include equal fluxes of all three flavors. Tau neutrinos with energies above a few PeV will produce characteristic signatures known as double-bangs and lollipops. In contrast to searches for cosmological electron and muon neutrinos, which must contend with backgrounds from atmospheric neutrinos, tau neutrinos are expected to be background-free. Thus far no searches for tau neutrino events with these characteristic signatures have been performed because their detection requires a kilometer-scale detector. In this talk, we will present current results from several methods for searching for high energy tau neutrinos in IceCube.
    • 0484: Search for quantum gravity with IceCube and high energy atmospheric neutrinos
    • Warren Huelsnitz and John Kelley for the IceCube Collaboration
    • Abstract: We present the expected sensitivity of an analysis that will use data from the IceCube Neutrino Observatory to search for distortions in the energy or directional dependence of atmospheric neutrinos. Deviations in the energy and zenith angle distributions of atmospheric neutrinos due to Lorentz invariance violation or quantum decoherence could be a signature of quantum gravity in the neutrino sector. Additionally, a periodic variation as a function of right ascension is a possible consequence of a Lorentz-violating preferred frame. We use a likelihood method to constrain deviations in the energy and zenith angle distributions and a discrete Fourier transform method to constrain a directional asymmetry in right ascension. In the absence of new physics, the likelihood method can also constrain conventional and prompt atmospheric neutrino flux models. Results from a similar analysis using data from the AMANDA-II detector are also discussed.
    • 0970: A First All-Particle Cosmic Ray Energy Spectrum From IceTop
    • Fabian Kislat, Stefan Klepser, Hermann Kolanoski and Tilo Waldenmaier for the IceCube Collaboration
    • Abstract: The IceTop air shower array is presently under construction at the geographic South Pole as part of the IceCube Observatory. It will consist of 80 stations which are pairs of Ice-Cherenkov tanks covering an area of 1 km2. In this paper a first analysis of the cosmic ray energy spectrum in the range 2 ⋅ 1015 eV to 1017 eV is presented using data taken in 2007 with 26 IceTop stations. The all-particle spectrum has been derived by unfolding the raw spectrum using response matrices for different mass compositions of the primaries. Exploiting the zenith angle dependence of the air shower development we have been able to constrain the range of possible composition models.
    • 0518: Reconstruction of IceCube coincident events and study of composition-sensitive observables using both the surface and deep detector
    • Tom Feusels, Jonathan Eisch and Chen Xu for the IceCube Collaboration
    • Abstract: The combined information from cosmic ray air showers that trigger both the surface and underground parts of the IceCube Neutrino Observatory allows the reconstruction of both the energy and mass of the primary particle through the knee region of the energy spectrum and above. The properties of high-energy muon bundles, created early in the formation of extensive air showers and capable of penetrating deep into the ice, are related to the primary energy and composition. New methods for reconstructing the direction and composition-sensitive properties of muon bundles are shown. Based on a likelihood minimization procedure using IceCube signals, and accounting for photon propagation, ice properties, and the energy loss processes of muons in ice, the muon bundle energy loss is reconstructed. The results of the high-energy muon bundle reconstruction in the deep ice and the reconstruction of the lateral distribution of low energy particles in the surface detector can be combined to study primary composition and energy. The performance and composition sensitivity for both simulated and experimental data are discussed.
    • 0737: Small air showers in IceTop
    • Bakhtiyar Ruzybayev, Shahid Hussain, Chen Xu and Thomas Gaisser for the IceCube Collaboration
    • Abstract: IceTop is an air shower array that is part of the IceCube Observatory currently under construction at the geographic South Pole [1]. When completed, it will consist of 80 stations covering an area of 1 km2. Previous analyzes done with IceTop studied the events that triggered five or more stations, leading to an effective energy threshold of about 0.5 PeV [2]. The goal of this study is to push this threshold lower, into the region where it will overlap with direct measurements of cosmic rays which currently have an upper limit around 300 TeV [3]. We select showers that trigger exactly three or exactly four adjacent surface stations that are not on the periphery of the detector (contained events). This extends the energy threshold down to 150 TeV.
    • 1429: Cosmic Ray Composition using SPASE-2 and AMANDA-II
    • K. Andeen and K. Rawlins For the IceCube Collaboration
    • Abstract: The precise measurement of cosmic ray mass composition in the region of the knee (3 PeV) is critical to understanding the origin of high energy cosmic rays. Therefore, air showers have been observed at the South Pole using the SPASE-2 surface array and the AMANDA-II neutrino telescope which simultaneously measure the electronic air shower component at the surface and the muonic air shower component in deep ice, respectively. These two components, together with a Monte Carlo simulation and a well-understood analysis method will soon yield the relative cosmic ray composition in the knee region. We report on the capabilities of this analysis.
    • 0519: Study of High pT Muons in IceCube (0909.0055)
    • Lisa Gerhardt and Spencer Klein for the IceCube Collaboration
    • Abstract: Muons with a high transverse momentum (pT) are produced in cosmic ray air showers via semileptonic decay of heavy quarks and the decay of high pT kaons and pions. These high pT muons have a large lateral separation from the shower core muon bundle. IceCube is well suited for the detection of high pT muons. The surface shower array can determine the energy, core location and direction of the cosmic ray air shower while the in-ice array can reconstruct the energy and direction of the high pT muon. This makes it possible to measure the decoherence function (lateral separation spectrum) at distances greater than 150 meters. The muon pT can be determined from the muon energy (measured by dE/dx) and the lateral separation. The high pT muon spectrum may also be calculated in a perturbative QCD framework; this spectrum is sensitive to the cosmic-ray composition.
    • 1340: Large Scale Cosmic Rays Anisotropy With IceCube (0907.0498)
    • Rasha U Abbasi, Paolo Desiati and Juan Carlos Velez for the IceCube Collaboration
    • Abstract: We report on a study of the anisotropy in the arrival direction of cosmic rays with a median energy per Cosmic Ray (CR) particle of ∼ 14 TeV using data from the IceCube detector. IceCube is a neutrino observatory at the geographical South Pole, when completed it will comprise 80 strings plus 6 additional strings for the low energy array Deep Core. The strings are deployed in the deep ice between 1,450 and 2,450 meters depth, each string containing 60 optical sensors. The data used in this analysis are the data collected from April 2007 to March 2008 with 22 deployed strings. The data contain ∼ 4.3 billion downward going muon events. A two-dimensional skymap is presented with an evidence of 0.06% large scale anisotropy. The energy dependence of this anisotropy at median energies per CR particle of 12 TeV and 126 TeV is also presented in this work. This anisotropy could arise from a number of possible effects; it could further enhance the understanding of the structure of the galactic magnetic field and possible cosmic ray sources.
    • 1398: Atmospheric Variations as observed by IceCube
    • Serap Tilav, Paolo Desiati, Takao Kuwabara, Dominick Rocco, Florian Rothmaier, Matt Simmons, Henrike Wissing for the IceCube Collaboration
    • Abstract: We have measured the correlation of rates in IceCube with long and short term variations in the South Pole atmosphere. The yearly temperature variation in the middle stratosphere (30-60 hPa) is highly correlated with the high energy muon rate observed deep in the ice, and causes a ±10% seasonal modulation in the event rate. The counting rates of the surface detectors, which are due to secondary particles of relatively low energy (muons, electrons and photons), have a negative correlation with temperatures in the lower layers of the stratosphere (40-80 hPa), and are modulated at a level of ±5%. The region of the atmosphere between pressure levels 20-120 hPa, where the first cosmic ray interactions occur and the produced pions/kaons interact or decay to muons, is the Antarctic ozone layer. The anti-correlation between surface and deep ice trigger rates reflects the properties of pion/kaon decay and interaction as the density of the stratospheric ozone layer changes. Therefore, IceCube closely probes the ozone hole dynamics, and the temporal behavior of the stratospheric temperatures.
    • 1251: Supernova Search with the AMANDA / IceCube Detectors (0908.0441)
    • Thomas Kowarik, Timo Griesel, Alexander Piégsa for the IceCube Collaboration
    • Abstract: Since 1997 the neutrino telescope AMANDA at the geographic South Pole has been monitoring our Galaxy for neutrino bursts from supernovae. Triggers were introduced in 2004 to submit burst candidates to the Supernova Early Warning System SNEWS. From 2007 the burst search was extended to the much larger IceCube telescope, which now supersedes AMANDA. By exploiting the low photomultiplier noise in the antarctic ice (on average 280 Hz for IceCube), neutrino bursts from nearby supernovae can be identified by the induced collective rise in the pulse rates. Although only a counting experiment, IceCube will provide the world's most precise measurement of the time profile of a neutrino burst near the galactic center. The sensitivity to neutrino properties such as the θ13 mixing angle and the neutrino hierarchy are discussed as well as the possibility to detect the deleptonization burst.
    • 1352: Physics Capabilities of the IceCube DeepCore Detector (0907.2263)
    • Christopher Wiebusch for the IceCube Collaboration
    • Abstract: IceCube-DeepCore is a compact Cherenkov Detector located in the clear ice of the bottom center of the IceCube Neutrino Telescope. its purpose is to enhance the sensitivity of IceCube for low neutrino energies (< 1 TeV) and to lower the detection threshold of IceCube by about an order of magnitude to below 10GeV. The detector is formed by 6 additional strings of 360 high quantum efficiency phototubes together with the 7 central IceCube strings. The improved sensitivity will provide an enhanced sensitivity to probe a range of parameters of dark matter models not covered by direct experiments. It opens a new window for atmospheric neutrino oscillation measurements of νμ disappearance or ντ appearance in an energy region not well tested by previous experiments, and enlarges the field of view of IceCube to a full sky observation when searching for potential neutrino sources. The first string was successfully installed in January 2009, commissioning of the full detector is planned early 2010.
    • 1336: Fundamental Neutrino Measurements with IceCube DeepCore
    • Darren Grant, D. Jason Koskinen, and Carsten Rott for the IceCube collaboration
    • Abstract: The recent deployment of the first string of DeepCore, a low-energy extension of the IceCube neutrino observatory, offers new opportunities for fundamental neutrino physics using atmospheric neutrinos. The energy reach of DeepCore, down to ∼ 10 GeV, will allow measurements of atmospheric muon neutrino disappearance at a higher energy regime than any past or current experiment. In addition to a disappearance measurement, a flavor-independent statistical analysis of cascade-like events opens the door for the measurement of tau neutrino appearance via a measurable excess of cascade-like events. In the event of a relatively large value of sin213, a multi-year measurement of the suppression of muon neutrino disappearance due to earth matter effects may show a measurable dependence on the sign of the mass hierarchy (normal vs. inverted).
    • 1237: Implementation of an active veto against atmospheric muons in IceCube DeepCore
    • Olaf Schulz, Sebastian Euler and Darren Grant for the IceCube Collaboration
    • Abstract: The IceCube DeepCore [1] has been designed to lower the energy threshold and broaden the physics capabilities of the IceCube Neutrino Observatory. A crucial part of the new opportunities provided by DeepCore is offered by the possibility to reject the background of atmospheric muons. This can be done by using the large instrumented volume of the standard IceCube configuration around Deep-Core as an active veto region. By thus restricting the expected signal to those neutrino events with an interaction vertex inside the central DeepCore region, it is possible to look for neutrinos from all directions, including the Southern Hemisphere that was previously not accessible to IceCube. A reduction of the atmospheric muon background below the expected rate of neutrinos is provided by first vetoing events in DeepCore with causally related hits in the veto region. In a second step the potential starting vertex of a muon track is reconstructed and its credibility is estimated using a likelihood method. Events with vertex positions outside of DeepCore or with low starting probabilities are rejected. We present here these newly developed veto and vertex reconstruction techniques and present in detail their capabilities in background rejection and signal efficiency that have been obtained so far from full Monte Carlo studies.
    • 1293: Acoustic detection of high energy neutrinos in ice: Status and results from the South Pole Acoustic Test Setup (0908.3251 – revised)
    • Freija Descamps for the IceCube Collaboration
    • Abstract: The feasibility and specific design of an acoustic neutrino detection array at the South Pole depend on the acoustic properties of the ice. The South Pole Acoustic Test Setup (SPATS) has been built to evaluate the acoustic characteristics of the ice in the 1 to 100 kHz frequency range. The most recent results of SPATS are presented.
    • 0903: Sensor development and calibration for acoustic neutrino detection in ice (0907.3561)
    • Timo Karg, Martin Bissok, Karim Laihem, Benjamin Semburg, and Delia Tosi for the IceCube collaboration
    • Abstract: A promising approach to measure the expected low flux of cosmic neutrinos at the highest energies (E > 1 EeV) is acoustic detection. There are different in-situ test installations worldwide in water and ice to measure the acoustic properties of the medium with regard to the feasibility of acoustic neutrino detection. The parameters of interest include attenuation length, sound speed profile, background noise level and transient backgrounds. The South Pole Acoustic Test Setup (SPATS) has been deployed in the upper 500 m of drill holes for the IceCube neutrino observatory at the geographic South Pole. In-situ calibration of sensors under the combined influence of low temperature, high ambient pressure, and ice-sensor acoustic coupling is difficult. We discuss laboratory calibrations in water and ice. Two new laboratory facilities, the Aachen Acoustic Laboratory (AAL) and the Wuppertal Water Tank Test Facility, have been set up. They offer large volumes of bubble free ice (3 m3) and water (11 m3) for the development, testing, and calibration of acoustic sensors. Furthermore, these facilities allow for verification of the thermoacoustic model of sound generation through energy deposition in the ice by a pulsed laser. Results from laboratory measurements to disentangle the effects of the different environmental influences and to test the thermoacoustic model are presented.

Papers Related To IceCube

    • 0466: A new method for identifying neutrino events in IceCube data
    • Dmitry Chirkin
    • Abstract: A novel approach for selecting high-quality muon neutrino events in IceCube data is presented. The rate of air shower events mis-reconstructed as signal is first reduced via the use of the geometrical (software) trigger. The final event selection is performed with a machine-learning method, designed specifically for IceCube data. It takes into account some generic properties of IceCube events, e.g., the fact that separation of signal from background is more difficult (requiring tighter cuts on the quality parameters) for horizontal rather than vertically up-going tracks. The method compares favorably to other techniques in situations with both high and low simulation statistics.
    • 0395: Muon Production of Hadronic Particle Showers in Ice and Water
    • Sebastian Panknin, Julien Bolmont, Marek Kowalski and Stephan Zimmer
    • Abstract: One of the neutrino signatures in Cerenkov neutrino detectors are isolated, particle showers induced by neutrinos of all flavors. Hadronic showers can produce muons during the shower development and the appearance of the showers can change significantly by such high-energy muons. We use a modified version of the air shower simulation program CORSIKA for the simulation of the generation of muons in salt water. We discuss how the results can be applied for ice. In addition, a simple analytical model is derived, that provides scaling relations for the muon energy spectrum and its dependence on the primary particle.
    • 0642: Muon bundle energy loss in deep underground detector
    • Xinhua Bai, Dmitry Chirkin, Thomas Gaisser, Todor Stanev and David Seckel
    • Abstract: High energy air showers contain bundles of muons that can penetrate deep underground. Study of these high energy muons can reveal the cosmic ray primary composition and some features of the hadronic interactions. In an underground neutrino experiment like IceCube, high energy muons are also of interest because they are the dominant part of the neutrino background. We study muon bundle energy loss in deep ice by full Monte Carlo simulation to define its fluctuations and relation to the cosmic ray primary nuclei. An analytical formula of muon bundle mean energy loss is compared with the Monte Carlo result. We also use the simulation to set the background for muons with catastrophic energy loss much higher than those of normal muon bundles.
    • 0542: Constraints on Neutrino Interactions at energies beyond 100 PeV with Neutrino Telescopes
    • Shigeru Yoshida
    • Abstract: A search for extremely high energy cosmic neutrinos has been carried out with the IceCube Neutrino Observatory. These event are neutrino-induced energetic charged leptons and their rate depends on the neutrino-nucleon cross-sections. The resultant event rate has implications for possible new physics beyond the standard model as it is predicted that the cross-sections can be much higher than the standard particle physics prediction if we live in more than four space-time dimensions. In this study we show the capability of neutrino telescopes such as IceCube to constrain neutrino cross-sections at energies beyond 107 GeV. The constraints are obtained as a function of the extraterrestrial neutrino flux in the relevant energy range, which accounts for the astrophysical uncertainty of neutrino production models.
    • 0006: Constraints on Extragalactic Point Source Flux from Diffuse Neutrino Limits
    • Andrea Silvestri and Steven W. Barwick
    • Abstract: We constrain the maximum flux from extragalactic neutrino point sources by using diffuse neutrino flux limits. We show that the maximum flux from extragalactic point sources is E2 (dNν /dE) ≤ 5.1 × 10−9 (Lν /1045 erg/s)1/3 GeV cm−2 s−1 from an ensemble of sources with average neutrino luminosity per decade, Lν. It depends only slightly on factors such as the inhomogeneous matter density distribution in the local universe, the luminosity distribution, and the assumed spectral index.
    • 0418: Study of electromagnetic backgrounds in the 25-300 MHz frequency band at the South Pole
    • Jan Auffenberg, Dave Bessony, Tom Gaisser, Klaus Helbing, Timo Karg, Albrecht Karle,and Ilya Kravchenko
    • Abstract: Extensive air showers are detectable by radio signals with a radio surface detector. A promising theory of the dominant emission process is the coherent synchrotron radiation emitted by e+ e- shower particles in the Earth's magnetic field (geosynchrotron effect). A radio air shower detector can extend IceTop, the air shower detector on top of IceCube. This could increase the sensitivity of IceTop to higher shower energies and for inclined showers significantly. Muons from air showers are a major part of the background of the neutrino telescope IceCube. Thus a surface radio air shower detector could act as a veto detector for this muonic background. Initial radio background measurements with a single antenna in 2006 revealed a continuous electromagnetic background promising a low energy threshold of radio air shower detector. However, short pulsed radio interferences can mimic real signals and have to be identified in the frequency range of interest. These properties of the electromagnetic background are being measured at the South Pole during the Antarctic winter 2009 with two different types of surface antennas. In total four antennas are placed at distances ranging up to 400m from each other. They are read out using the RICE DAQ with an amplitude threshold trigger and a minimum bias trigger. Results of the first three months of measurement are presented.
    • 0238: Neutrino signal from -ray loud binaries powered by high-energy protons
    • Andrii Neronov and Mathieu Ribordy
    • Abstract: We consider hardonic model of activity of Galactic γ-ray-loud binaries. We show that in such a model multi-TeV neutrino flux from the source can be much higher and/or harder than the detected TeV γ-ray flux. This is related to the fact that most of the neutrinos can be produced in ρρ interactions close to the bright massive star, in a region which is optically thick for the TeV γ-rays. Considering the example of LS I +61° 303, we show that the expected neutrino signal, detectable within ∼ 3 years of exposure with ICECUBE, will be marginally sufficient to constrain the spectral characteristics of neutrino signal.
    • 0249: Acoustic sensor development for ultra high energy neutrino detection
    • Matt Podgorski and Mathieu Ribordy
    • Abstract: The GZK neutrino flux characterization would give insights into cosmological source evolution, source spectra and composition at injection from the partial recovery of the degraded information carried by the ultra high energy cosmic rays. The flux is expected to be at levels necessitating a much larger instrumented volume (>100 km3) than those currently operating. First suggested by Askaryan, both radio and acoustic detection techniques could render this quest possible thanks to longer wave attenuation lengths (predicted to exceed a kilometer) allowing for a much sparser instrumentation compared to optical detection technique. We present the current acoustic R&D activities at our lab developing adapted devices, report on the obtained sensitivities and triangulation capabilities we obtained, and define some of the requirements for the construction of a full scale detector.