Symmetrizing the signal distribution of radio emission from inclined air showers

TL;DR

This paper introduces a model to symmetrize radio signal distributions from inclined air showers, enabling more accurate reconstruction of cosmic-ray energies by compensating for asymmetries caused by geomagnetic and charge-excess effects.

Contribution

The paper presents a novel model that explicitly corrects for asymmetries in radio signals from inclined air showers, improving the accuracy of cosmic-ray energy estimation.

Findings

Effective removal of early-late asymmetries

Universal parameterization of charge-excess fraction

Enhanced precision in radio-based air-shower reconstruction

Abstract

Radio detection of inclined air showers currently receives special attention. It can be performed with very sparse antenna arrays and yields a pure measurement of the electromagnetic air-shower component, thus delivering information that is highly complementary to the measurement of the muonic component using particle detectors. However, radio-based reconstruction of inclined air showers is challenging in light of asymmetries induced in the radio-signal distribution by early-late effects as well as the superposition of geomagnetic and charge-excess radiation. We present a model for the signal distribution of radio emission from inclined air showers which allows explicit compensation of these asymmetries. In a first step, geometrical early-late asymmetries are removed. Secondly, a universal parameterization of the charge-excess fraction as a function of the air-shower geometry, the atmospheric density profile and the lateral distance from the shower axis is used to compensate for the charge-excess contribution to the signal. The resulting signal distribution of the pure geomagnetic emission is then fit with a rotationally symmetric lateral distribution function, the area integration of which yields the radiation energy as an estimator for the cosmic-ray energy. We present the details and performance of our model, which lays the foundation for robust and precise reconstruction of inclined air showers from radio measurements.