Radio measurements of the energy and the depth of the shower maximum of cosmic-ray air showers by Tunka-Rex

TL;DR

This paper demonstrates that radio measurements with Tunka-Rex can reliably reconstruct the energy and depth of maximum of cosmic-ray air showers, showing good agreement with established air-Cherenkov methods and promising precision.

Contribution

The study introduces a radio-based reconstruction method for cosmic-ray air showers that is validated against established techniques, achieving comparable energy precision and first direct correlation for Xmax.

Findings

Radio reconstruction yields energy consistent with air-Cherenkov measurements.

Achieved approximately 40 g/cm^2 resolution for Xmax.

Energy precision is comparable to 15% of established methods.

Abstract

We reconstructed the energy and the position of the shower maximum of air showers with energies $E \gtrsim 100 $PeV applying a method using radio measurements performed with Tunka-Rex. An event-to-event comparison to air-Cherenkov measurements of the same air showers with the Tunka-133 photomultiplier array confirms that the radio reconstruction works reliably. The Tunka-Rex reconstruction methods and absolute scales have been tuned on CoREAS simulations and yield energy and $X_{\mathrm{max}}$ values consistent with the Tunka-133 measurements. The results of two independent measurement seasons agree within statistical uncertainties, which gives additional confidence in the radio reconstruction. The energy precision of Tunka-Rex is comparable to the Tunka-133 precision of $15 %$, and exhibits a $20 %$ uncertainty on the absolute scale dominated by the amplitude calibration of the antennas. For $X_{\mathrm{max}}$, this is the first direct experimental correlation of radio measurements with a different, established method. At the moment, the $X_{\mathrm{max}}$ resolution of Tunka-Rex is approximately $40 $g/cm$^2$. This resolution can probably be improved by deploying additional antennas and by further development of the reconstruction methods, since the present analysis does not yet reveal any principle limitations.