Detection of Radio Emission by Cosmic Rays with the BEACON Prototype

The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a novel detector concept consisting of many radio interferometers placed on mountaintops, searching for the radio emission of upgoing extensive air showers created when ultrahigh energy tau neutrinos skim the Earth. The BEACON prototype is located at the White Mountain Research Station in California at an elevation of 3.8 km and has been operating since 2018. It consists of a phased array of 4 custom, crossed-dipole antennas with a 30-80 MHz bandwidth. The prototype has demonstrated the ability to trigger on impulsive RF events in the presence of background noise, with at least one such event likely being a cosmic ray. The threshold of the prototype can be validated by a measurement of the cosmic ray flux, allowing us to better predict the sensitivity of a full-size BEACON to tau neutrinos. We discuss the goals of the BEACON concept, the status of the prototype, and an ongoing cosmic ray search which utilizes a convolutional neural network trained on simulated cosmic ray waveforms.