K. Hanson

Measurement Of The Anisotropy Of Cosmic-Ray Arrival Directions With Icecube

We report the first observation of an anisotropy in the arrival direction of cosmic rays with energies in the multi-TeV region in the Southern sky using data from the IceCube detector. Between 2007 June and 2008 March, the partially deployed IceCube detector was operated in a configuration with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 m inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic-ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the southern sky. The data include 4.3 billion muons produced by downward-going cosmic-ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of similar to 20 TeV. Their arrival direction distribution exhibits an anisotropy in right ascension with a first-harmonic amplitude of (6.4 +/- 0.2 stat. +/- 0.8 syst.) x 10(-4).

The observation of up-going charged particles produced by high energy muons in underground detectors

An experimental study of the production of up-going charged particles in inelastic interactions of down-going underground muons is reported, using data obtained from the MACRO detector at the Gran Sasso Laboratory. In a sample of 12.2×106 single muons, corresponding to a detector livetime of 1.55 y, 243 events are observed having an up-going particle associated with a down-going muon. These events are analysed to determine the range and emission angle distributions of the up-going particle, corrected for detection and reconstruction efficiency. Measurements of the muon neutrino flux by underground detectors are often based on the observation of through-going and stopping muons produced in νμ interactions in the rock below the detector. Up-going particles produced by an undetected down-going muon are a potential background source in these measurements. The implications of this background for neutrino studies using MACROAbstract An experimental study of the production of up-going charged particles in inelastic interactions of down-going underground muons is reported, using data obtained from the MACRO detector at the Gran Sasso Laboratory. In a sample of 12.2 × 106 single muons, corresponding to a detector lifetime of 1.55y, 243 events are observed having an up-going particle associated with a down-going muon. These events are analysed to determine the range and emission angle distributions of the up-going particle, corrected for detection and reconstruction efficiency. Measurements of the muon neutrino flux by underground detectors are often based on the observation of through-going and stopping muons produced in νμ interactions in the rock below the detector. Up-going particles produced by an undetected down-going muon are a potential background source in these measurements. The implications of this background for neutrino studies using MACRO are discussed.

Performance of two Askaryan Radio Array stations and first results in the search for ultrahigh energy neutrinos

Ultrahigh energy neutrinos are interesting messenger particles since, if detected, they can transmit exclusive information about ultrahigh energy processes in the Universe. These particles, with energies above 1016 eV, interact very rarely. Therefore, detectors that instrument several gigatons of matter are needed to discover them. The ARA detector is currently being constructed at the South Pole. It is designed to use the Askaryan effect, the emission of radio waves from neutrino-induced cascades in the South Pole ice, to detect neutrino interactions at very high energies. With antennas distributed among 37 widely separated stations in the ice, such interactions can be observed in a volume of several hundred cubic kilometers. Currently three deep ARA stations are deployed in the ice, of which two have been taking data since the beginning of 2013. In this article, the ARA detector “as built” and calibrations are described. Data reduction methods used to distinguish the rare radio signals from overwhelming backgrounds of thermal and anthropogenic origin are presented. Using data from only two stations over a short exposure time of 10 months, a neutrino flux limit of 1.5 × 10−6 GeV=cm2=s=sr is calculated for a particle energy of 1018 eV, which offers promise for the full ARA detector.

IceRay: An IceCube-centered Radio-Cherenkov GZK Neutrino Detector

We discuss design considerations and simulation results for IceRay, a proposed large-scale ultra-high energy (UHE) neutrino detector at the South Pole. The array is designed to detect the coherent Askaryan radio emission from UHE neutrino interactions in the ice, with the goal of detecting the cosmogenic neutrino flux with reasonable event rates. Operating in coincidence with the IceCube neutrino detector would allow complete calorimetry of a subset of the events. We also report on the status of a testbed IceRay station which incorporates both ANITA and IceCube technology and will provide year-round monitoring of the radio environment at the South Pole.

An extended-range Ethernet and clock distribution circuit for distributed sensor networks

This paper describes a high-speed Ethernet-based data and clock network for applications which require an array of multiple sensor nodes distributed over distances of up to 250 m from a central hub. Speeds of up to 100 Mbit/sec and clock skew at the level of 50 ps are achievable using commercially available network-grade twisted pair cables and low-power Ethernet transceiver circuits. No fiber optic components are necessary. A specific application of this technology is presented: the ARA neutrino telescope located at the South Pole.

The Askar'yan radio array

We are developing an antenna array to be installed in boreholes extending 200 m below the ice surface at the geographic South Pole. ARA will cover a fiducial area of 150 km2, chosen to ensure the detection of the flux of neutrinos guaranteed by observations of the GZK cutoff by HiRes and the Pierre Auger Observatory. The first components of ARA were installed during the austral summer of 2010-2011. After three years of operation, the full array sensitivity will exceed that of any other instrument in the 0.1-10 EeV energy range by an order of magnitude. The primary goal of the ARA experiment is to establish the absolute cosmogenic neutrino flux through a modest number of events. This talk will describe the array, its science goals, and give the current status of the project.

PMm2: R&D on triggerless acquisition for next generation neutrino experiments

The next generation of proton decay and neutrino experiments, the post-SuperKamiokande detectors, such as those that will take place in megaton size water tanks, will require very large surfaces of photo-detection and will produce a large volume of data. Even with large hemispherical photomultiplier tubes (PMTs), the expected number of channels should reach hundreds of thousands. An ANR funded R&D program to implement a solution is presented here. The very large surface of photo-detection is segmented in macro pixels consisting of an array (2 × 2 m2) of 16 hemispherical 12-inch PMTs connected to autonomous underwater front-end electronics working in a triggerless data acquisition mode. The array is powered by a common high voltage and only one data cable allows the connection by network to the surface controller. This architecture allows a considerable reduction of the cost and facilitates the industrialization. This paper presents the complete architecture of the prototype system and tests results with 16 8-inch PMTs, validating the whole electronics, the built-in gain adjustment and the calibration principle.

Construction Status and Future of the IceCube Neutrino Observatory

The IceCube neutrino telescope nears the end of its second running season having collected a sample of over 2 × 109 triggered events. While the majority of these events are cosmic ray muons, the detector is already sufficiently well understood to allow identification of neutrinoinduced muon candidate events from the CR background. The production of optical module instrumentation is now well-established, the modules themselves are functioning properly with low failure rate, and it has been proven that the hot water drill can deliver the holes needed for deployment of these instruments. The project plans to deploy 12-14 strings each year during the next several austral summers to bring the detector volume to 1 km3.

Probing the radar scattering cross-section for high-energy particle cascades in ice

Recently the radar scattering technique to probe neutrino induced particle cascades above PeV energies in ice was investigated. The feasibility of the radar detection method was shown to crucially depend on several up to now unknown plasma properties, such as the plasma lifetime and the free charge collision rate. To determine these parameters, a radar scattering experiment was performed at the Telescope Array Electron Light Source facility, where a beam of high-energy electrons was directed in a block of ice. The induced ionization plasma was consequently probed using a radar detection set-up detecting over a wide frequency range from 200 MHz up to 2 GHz. First qualitative results of this experiment will be presented.

Extending the IceCube DAQ system by integration of the generic high-speed sorter module TESS

In the extreme environment of Antarctica at the South Pole, the IceCube experiment, the worlds first kilometer-scale neutrino telescope, collects cosmic ray events. IceCube consists of over 5000 digital optical sensor modules (DOMs) deployed on 86 instrumentation lines each extending 2.5 km deep in the antarctic ice. The array of optical modules monitors the Cherenkov light emitted by passing radiation, which, when digitized and timestamped to nanosecond precision, is used as input to sophisticated reconstruction algorithms that determine the direction, energy, and type of the incident cosmic ray event. In order to achieve this goal, the IceCube data acquisition system merges the digital data streams from each photodetector into a single time-ordered list which is presented to online triggers that determine, in realtime, whether or not a given pattern of hits is noise or signal. At the present time, the data provided to the triggers is limited by the performance of sorting and merging algorithms: the 500 Hz raw data rate from each sensor (2.5 MHz array aggregate rate) is beyond the capability of the central sort and merge. The current solution adopted by the IceCube detector is to impose a hardware-based pre-trigger coincidence on hits emanating from the DOMs which reduces the rate by a factor of 20. While this pre-trigger coincidence has negligible impact on the detector sensitivity for the principal goal of high-energy neutrinos from galactic or extragalactic sources, other low-energy physics searches are affected. This presentation details work done to develop and implement a system, TESS, which is capable of merging the full raw data stream being produced by the IceCube DOMs. TESS is designed as a pipelined architecture with three major modules: server, selector and the client glued together by circular buffers. The three modules runs in only three threads and since the architecture is self synchronizing and uses no data copying maximum performance can be achieved for global sorting of payloads. The TESS sorting architecture was originally designed to provide a globally sorted data stream for triggers targeting low-energy events from annihilation of hypothesized dark-matter particles, however its utility is generalizable to any IceCube trigger which requires inspection of the full data stream. The IceCube online supernova detection system is a notable example. Moreover, the algorithm is generic to any system involving multiple, independently sorted data streams which must be merged into a single sorted data stream.