Session T9: High Energy Neutrino Detection

Ray Propagation in Ice for Radio Cherenkov Neutrino Experiments

Understanding the propagation of radio signals in ice is important for existing and future south polar neutrino experiments to observe high-energy astrophysical neutrinos via radio emission from the Askaryan effect. This includes the Askaryan Radio Array (ARA), a new detector being constructed, which is planned to cover an approximately 80 $km^2$ area, and to detect GZK neutrinos at a rate of a few per year, with sensors placed at relatively shallow depths. In order to both simulate the behavior of the detector and reconstruct collected data, the paths of the radio signals through the ice must be accurately calculated, which involves nontrivial optics problems arising from the depth dependent properties of the naturally-occurring antarctic ice. Since analytical solutions for the ray paths are not known, it is necessary to use numerical ray-tracing. We show how existing optics results can be applied to increase the efficiency of the ray-tracing calculations, and present initial results with existing radio experiments using these tools.   

Point-to-point measurement of radio frequency attenuation in South Polar ice

For ultra high energy (UHE) electromagnetic showers in a dense medium, radio frequency Cherenkov emission is enhanced due to the Askaryan effect. Present and future detectors such as RICE, ANITA, ARIANNA and the Askaryan Radio Array (ARA) exploit this effect to detect UHE neutrinos interacting with Antarctic ice. The radio frequency electromagnetic wave attenuation length (the distance over which signal amplitude diminishes by a factor of $1/e$ due to absorption or scattering) is of tantamount importance as it determines the size scale and effective volume of these detectors. Previous attenuation measurements rely on reflections off the bedrock of signals from a surface-mounted transmitter. Using RICE in-ice transmitters and IceCube Radio Extension in-ice receivers, we are conducting a point-to-point attenuation measurement in the upper 1500 meters of South Polar ice, the region of interest for planned near-surface detectors such as ARA. We will present the analysis method as well as preliminary results.   

Updates on IceCube's Radio Frequency extension

A variety of radio frequency (RF) detectors were deployed in the Antarctic ice as an enhancement to the optically-based IceCube Neutrino Observatory, and as a step towards a large-scale high-energy neutrino detector. This RF addition includes a set of 5 deep-deployed (300m-1400m) digitizing detectors, a shallow array ($\sim$35m) of transient detectors and a set of transmitters. All Are sensitive to frequencies between 200Mhz to 1GHz. We will review the hardware deployed, and present studies preformed with it including ice characteristics (attenuation and index of refraction), environmental noise and event reconstruction.   

Pre-Phase A Results from the ARIANNA Detector from the Antarctic seasons 2009-10 and 2010-11

The Antarctic Ross Ice-Shelf Antenna Neutrino Array is an experiment designed to detect cosmogenic neutrinos with energies in excess of 10$^{17}$ eV, including neutrinos created as by-products of cosmic-rays which undergo the GZK effect. ARIANNA is sensitive to down-going neutrinos because the GHz radiofrequency pulses they create, via the Askaryan effect, reflect off of the interface between the ocean and the ice-shelf. Here we present results from data collected during the 2009-2010 season. In addition, we discuss measurements describing the depth and attenuation of the ice-shelf, and reflectivity of the ice-ocean interface beneath the detector volume. Finally, we discuss data describing experimental modifications and upgrades being implemented for the upcoming seasons, including a new trigger and waveform digitizer.   

Characterizing the search for UHE neutrinos with the ARIANNA detector

The ARIANNA experiment exploits unique properties of the Ross Iceshelf, namely its radio transparency and its radio reflectivity at the ice-water boundary beneath the shelf, to search for UHE neutrinos. Simulation studies show that, with the full array, we expect to detect $\sim $40 GZK events/year using the ESS model. The excellent sensitivity results from the low energy threshold ($>$ 3x10$^{17}$ eV), large volume (513 km$^3$), continuous operation throughout the Antarctic summer, and viewing slightly more than half the sky. We have developed simulation tools to estimate the sensitivity to all neutrino flavors. In this talk, we will also present the angular and energy dependent sensitivity of the detector.   

ANITA-II Ultra-Relativistic Magnetic Monopole Search Strategy and Results

The ANITA (ANtarctic Impulsive Transient Antenna) experiment is a balloon borne antenna array designed to detect Cherenkov radiation produced by ultra-high energy neutrino-ice interactions. ANITA-II (2008-2009) was aloft for 31 days at an altitude of $\approx$ 35,000m. This large detector area and live time makes ANITA-II the most sensitive experiment to date for detection of the extended energy deposition trails left by ultra-relativistic magnetic monopoles interacting in Antarctic ice. I will discuss our search strategy and the results obtained.   

Monte Carlo studies for neutrino detection from Minna Bluff and other mountainsides in Antarctica

We present a simple Monte Carlo simulation for a possible neutrino detection experiment. The detector would be composed of an array of radio antennas on Minna Bluff, Antarctica, designed to detect Cherenkov radiation from ultra-high-energy neutrinos. The location, overlooking the Ross Ice Shelf, is ideal because of its proximity to McMurdo station. We show the validity of the results by comparing with the Monte Carlo simulation established for the ANITA (Antarctic Impulsive Transient Antenna) experiment. We also present new results on an attenuation length measurement of the ice shelf in the 200--1200 MHz range. Though the results predict less than one event per year, we discovered a possible alternative of placing the detector on the Transantarctic Mountains to overlook the deeper ice sheet.