Radar detection of cosmic-ray and neutrino induced cascades

Abstract

An ultra high energy particle, incident upon the earth, will produce a cascade of particles upon interaction. Detection of this cascade holds the key to understanding the properties of the primary-what it was, how much energy it carried, and maybe even where it came from. Of the many strategies developed over the course of the last century to detect such cascades, the radar technique is one of the latest to be explored with interest. For high enough incident energies, the relativistic progression of the cascade through a medium will produce a cloud of ionization that may become dense enough to reflect incident radio-frequency (RF) fields. If so, a broadcasting transmitter and distant receiver could feasibly detect cascades at very long baselines, thereby converting a massive volume of air or ice or sand or salt into a sensitive detector. Such an increase in volume opens up possibility of detecting events which occur on the order of 1km −2 yr −1 or less. In this dissertation, we present a detailed discussion of the radar detection method, focusing specifically on the detection of ultra high energy cosmic rays in the atmosphere, and ultra high energy neutrinos in dense material, such as ice. We will present the history and experimental efforts to date, and include the latest results from recent models and experiments seeking to address the radar problem. Ultimately, we suggest that the radar method is a promising one for the detection of 10 15 eV neutrinos which have interacted in a dense medium, such as the Antarctic ice.