Experimental search for coherent radar reflections from an electron-beam induced particle cascade

In development of a new detection scheme for the highest energy neutrinos, experiment T576 at SLAC was designed to detect a radar reflection from a high-energy particle cascade. High energy particles incident on dense materials (ice, salt, sand, etc.) will produce a cascade of secondary particles which pass relativistically through the material. As they do so, they kick out electrons from the material, forming a short-lived plasma. For high enough incident particle energies, this ionization density will be high enough to reflect incident radio frequency fields, and thereby allow for remote detection. The electron beam at SLAC, containing approximately N=10⁹ electrons at 10⁹ eV was used as a proxy for a single high energy neutrino of 10¹⁸ eV, and directed into a plastic target to produce a cascade. This cascade was interrogated with RF of various frequencies and amplitudes, and measured with a variety of receiving antennas. This talk will detail the discovery potential of - and challenges inherent to - the detection technique, outline the experimental goals of T576, discuss the measurements taken during two separate runs in 2018, and present preliminary results from the analysis.