Toward High Energy Neutrino Detection with the Radar Echo Telescope for Cosmic Rays (RET-CR)

The Radar Echo Telescope for Cosmic Rays (RET-CR) is a pathfinder experiment for the Radar Echo Telescope for Neutrinos (RET-N), a next-generation in-ice detection experiment for ultra high energy neutrinos. RET-CR will serve as the testbed for the radar echo method to probe high-energy particle cascades in nature, whereby a transmitted radio signal is reflected from the ionization left in its wake. This method, recently validated at SLAC experiment T576, shows promising preliminary sensitivity to neutrino-induced cascades above the energy range of optical detectors like IceCube. RET-CR intends to use an in-nature test beam: the dense, in-ice cascade produced when the air shower of an ultra high energy cosmic ray impacts a high-elevation ice sheet. This in-ice cascade, orders of magnitude more dense than the in-air shower that preceded it, is similar in profile and density to the expected cascade from a neutrino-induced cascade deep in the ice. RET-CR will be triggered using surface scintillator technology and will be used to develop, test, and deploy the hardware, firmware, and software needed for the eventual RET-N. We present the strategy, status, and design sensitivity of RET-CR, and discuss its application to eventual neutrino detection.