IceCube Science

📝 Abstract

We discuss the status of the kilometer-scale neutrino detector IceCube and its low energy upgrade Deep Core and review its scientific potential for particle physics. We subsequently appraise IceCube’s potential for revealing the enigmatic sources of cosmic rays. After all, this aspiration set the scale of the instrument. While only a smoking gun is missing for the case that the Galactic component of the cosmic ray spectrum originates in supernova remnants, the origin of the extragalactic component remains as inscrutable as ever. We speculate on the role of the nearby active galaxies Centaurus A and M87.

💡 Analysis

We discuss the status of the kilometer-scale neutrino detector IceCube and its low energy upgrade Deep Core and review its scientific potential for particle physics. We subsequently appraise IceCube’s potential for revealing the enigmatic sources of cosmic rays. After all, this aspiration set the scale of the instrument. While only a smoking gun is missing for the case that the Galactic component of the cosmic ray spectrum originates in supernova remnants, the origin of the extragalactic component remains as inscrutable as ever. We speculate on the role of the nearby active galaxies Centaurus A and M87.

📄 Content

IceCube Science Francis Halzen Department of Physics, University of Wisconsin, Madison, WI 53706, USA E-mail: halzen@icecube.wisc.edu Abstract. We discuss the status of the kilometer-scale neutrino detector IceCube and its low energy upgrade Deep Core and review its scientific potential for particle physics. We subsequently appraise IceCube’s potential for revealing the enigmatic sources of cosmic rays. After all, this aspiration set the scale of the instrument. While only a smoking gun is missing for the case that the Galactic component of the cosmic ray spectrum originates in supernova remnants, the origin of the extragalactic component remains as inscrutable as ever. We speculate on the role of the nearby active galaxies Centaurus A and M87.

1. The First Kilometer-Scale High Energy Neutrino Detector: IceCube A series of first-generation experiments[1] have demonstrated that high energy neutrinos with ∼10 GeV energy and above can be detected by observing the Cherenkov radiation from secondary particles produced in neutrino interactions inside large volumes of highly transparent ice or water instrumented with a lattice of photomultiplier tubes. The first second-generation detector, IceCube, is under construction at the geographic South Pole[2]. IceCube will consist of 80 kilometer-length strings, each instrumented with 60 10-inch photomultipliers spaced by 17 m. The deepest module is located at a depth of 2.450 km so that the instrument is shielded from the large background of cosmic rays at the surface by approximately 1.5 km of ice. The strings are arranged at the apexes of equilateral triangles 125m on a side. The instrumented detector volume is a cubic kilometer of dark, highly transparent and totally sterile Antarctic ice. The radioactive background is dominated by the instrumentation deployed into the natural ice. A surface air shower detector, IceTop, consisting of 160 Auger-style 2.7m diameter ice-filled Cherenkov detectors deployed pairwise at the top of each in-ice string, augments the deep-ice component by providing a tool for calibration, background rejection and cosmic ray studies. Each optical sensor consists of a glass sphere containing the photomultiplier and the electronics board that digitizes the signals locally using an on-board computer. The digitized signals are given a global time stamp with residuals accurate to less than 3 ns and are subsequently transmitted to the surface. Processors at the surface continuously collect the time- stamped signals from the optical modules; each functions independently. The digital messages are sent to a string processor and a global event trigger. They are subsequently sorted into the Cherenkov patterns emitted by secondary muon tracks that reveal the direction of the parent neutrino[3]. IceCube detects neutrinos with energies in excess of 0.1 TeV. An upgrade of the detector, dubbed Deep Core, consists of an infill of 6 strings with 60 DOMs with high quantum efficiency. They are mostly deployed in the highly transparent ice making up the bottom half of the arXiv:0901.4722v1 [astro-ph.HE] 29 Jan 2009 Figure 1. The IceCube detector, consisting of IceCube and IceTop and the low-energy sub- detector DeepCore. Also shown is the first-generation AMANDA detector. IceCube detector. Deep Core will decrease the threshold to ∼10 GeV over a significant fraction of IceCube’s fiducial volume and will be complete by February 2010; see Fig. 1. The main scientific goals of IceCube fall into broad categories: (i) Detect astrophysical neutrinos produced in cosmic sources with an energy density comparable to the energy density in cosmic rays[4]. Supernova remnants satisfy this requirement if they are indeed the sources of the galactic cosmic rays as first proposed by Zwicky; his proposal is a matter of debate after more than seventy years. The sources of the extragalactic cosmic rays naturally satisfy the prerequisite when particles accelerated near black holes, possibly the central engines of active galaxies or gamma ray bursts, collide with photons in the associated radiation fields. While the secondary protons may remain trapped in the acceleration region, approximately equal numbers of neutrons, neutral and charged pions escape. The energy escaping the source is therefore distributed between cosmic rays, gamma rays and neutrinos produced by the decay of neutrons and neutral and charged pions, respectively. We will elaborate on the potential of IceCube to reveal the sources of the cosmic rays; this goal is of primary importance as it sets the scale of the detector. (ii) As for conventional astronomy, neutrino astronomers observe the neutrino sky through the atmosphere. This is a curse and a blessing; the background of neutrinos produced by cosmic rays in interactions with atmospheric nuclei provides a beam essential for calibrating the instrument. It also presents us with an opportunity to do particle physics[5]. Especially unique is the energy range of the background atmospher

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