Measurement of the cosmic-ray energy spectrum above $10^{16}$ eV with the LOFAR Radboud Air Shower Array

TL;DR

This paper details the measurement of cosmic-ray energies above 10^16 eV using the LOFAR Radboud Air Shower Array, providing an independent energy reconstruction method based on radio signals.

Contribution

It introduces a new energy reconstruction technique for air showers using LOFAR radio data, validated against simulations and compatible with existing cosmic-ray spectra.

Findings

Reconstructed the cosmic-ray energy spectrum between 2×10^16 and 2×10^18 eV.

Results agree with literature and suggest a change in cosmic-ray composition.

Demonstrated the effectiveness of radio-based energy measurement.

Abstract

The energy reconstruction of extensive air showers measured with the LOFAR Radboud Air Shower Array (LORA) is presented in detail. LORA is a particle detector array located in the center of the LOFAR radio telescope in the Netherlands. The aim of this work is to provide an accurate and independent energy measurement for the air showers measured through their radio signal with the LOFAR antennas. The energy reconstruction is performed using a parameterized relation between the measured shower size and the cosmic-ray energy obtained from air shower simulations. In order to illustrate the capabilities of LORA, the all-particle cosmic-ray energy spectrum has been reconstructed, assuming that cosmic rays are composed only of protons or iron nuclei in the energy range between $\sim2\times10^{16}$ and $2\times10^{18}$ eV. The results are compatible with literature values and a changing mass composition in the transition region from a galactic to an extragalactic origin of cosmic rays.