Autonomous radiodetection of air showers with the TREND50 antenna array

TL;DR

The TREND50 array autonomously detected and identified air showers via radio signals in a quiet mountain environment, demonstrating the feasibility of radio-based cosmic-ray detection with low efficiency but promising for future large-scale projects.

Contribution

This work presents the first autonomous radio detection and identification of air showers using a self-triggered antenna array in a radio-quiet environment.

Findings

Detected 564 air shower candidates from 7×10^8 signals

Event directions match cosmic-ray simulations

Detection efficiency around 3%

Abstract

TREND50 is a radio detection setup of 50 self-triggered antennas working in the 50-100MHz frequency range and deployed in a radio-quiet valley of the Tianshan mountains (China). TREND50 achieved its goal: the autonomous radiodetection and identification of air showers. Thanks to a dedicated offine selection algorithm, 564 air shower candidates were indeed selected out of $7\cdot10^8$ transient radio signals recorded during the 314 live days of data taken during the first two years of operation of this setup (2011 and 2012). This event rate, as well as the distribution of the candidate directions of arrival, is consistent with what is expected from cosmic-ray-induced air showers according to simulations, assuming an additional $\sim$20% contamination of the final sample by background events. This result is obtained at the cost of a reduced air shower detection efficiency, estimated to be $\sim$3%. This low efficiency is mostly due to the large amount of dead time of the setup. This result paves the way for the GRANDProto35 experiment, the first stage of the GRAND project.