Status of air-shower measurements with sparse radio arrays (ARENA 2016)

TL;DR

This paper reviews the current state of radio detection techniques for cosmic-ray air showers, highlighting recent results, the potential for cost-effective large-area arrays, and ongoing developments to improve measurement accuracy and composition analysis.

Contribution

It provides a comprehensive summary of recent experimental results and discusses advancements in radio array design and analysis methods for cosmic-ray air-shower detection.

Findings

Sparse radio arrays can cover several km^2 at reasonable costs.

Radio detection can match the accuracy of fluorescence and Cherenkov techniques for energy measurement.

Current methods for determining Xmax are still under development, with LOFAR leading in precision.

Abstract

This proceeding gives a summary of the current status and open questions of the radio technique for cosmic-ray air showers, assuming that the reader is already familiar with the principles. It includes recent results of selected experiments not present at this conference, e.g., LOPES and TREND. Current radio arrays like AERA or Tunka-Rex have demonstrated that areas of several km^2 can be instrumented for reasonable costs with antenna spacings of the order of 200 m. For the energy of the primary particle such sparse antenna arrays can already compete in absolute accuracy with other precise techniques, like the detection of air-fluorescence or air-Cherenkov light. With further improvements in the antenna calibration, the radio detection might become even more accurate. For the atmospheric depth of the shower maximum, Xmax, currently only the dense array LOFAR features a precision similar to the fluorescence technique, but analysis methods for the radio measurement of Xmax are still under development. Moreover, the combination of radio and muon measurements is expected to increase the accuracy of the mass composition, and this around-the-clock recording is not limited to clear nights as are the light-detection methods. Consequently, radio antennas will be a valuable add-on for any air shower array targeting the energy range above 100 PeV.