A comparison of the cosmic-ray energy scales of Tunka-133 and KASCADE-Grande via their radio extensions Tunka-Rex and LOPES

TL;DR

This study compares the cosmic-ray energy scales of Tunka-133 and KASCADE-Grande experiments using their radio extensions Tunka-Rex and LOPES, demonstrating consistency within approximately 10% accuracy through calibrated radio measurements.

Contribution

It introduces a method to compare cosmic-ray energy scales of different experiments using radio measurements calibrated with a common reference source.

Findings

The energy scales of Tunka-133 and KASCADE-Grande are consistent within 10%.

Calibrated radio measurements can reliably compare different cosmic-ray experiments.

Radio detection provides an absolute energy scale for cosmic-ray air showers.

Abstract

The radio technique is a promising method for detection of cosmic-ray air showers of energies around $100\,$PeV and higher with an array of radio antennas. Since the amplitude of the radio signal can be measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. We show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. Using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments Tunka-133 and KASCADE-Grande, using their radio extensions, Tunka-Rex and LOPES, respectively. Due to the consistent amplitude calibration for Tunka-Rex and LOPES achieved by using the same reference source, this comparison reaches an accuracy of approximately $10\,\%$ - limited by some shortcomings of LOPES, which was a prototype experiment for the digital radio technique for air showers. In particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments KASCADE-Grande and Tunka-133 are consistent with each other on this level.