Energy and Xmax reconstruction of hadron-initiated showers in surface arrays

TL;DR

This paper adapts a photon-initiated shower reconstruction method to hadron primaries, enabling accurate energy and Xmax estimation in surface arrays with minimal bias and improved resolution.

Contribution

It introduces a unified calibration approach for hadron primaries in surface arrays, achieving low bias and high resolution in energy and Xmax reconstruction.

Findings

Energy can be inferred with 12% resolution using primary-specific calibration.

Mixed calibration maintains low bias with around 15% energy resolution.

Xmax can be determined with better than 7% resolution.

Abstract

The current methods to determine the primary energy in surface arrays are different when dealing with hadron or photon initiated showers. In this work, we adapt a method previously developed for photon-initiated showers to hadron primaries. We determine the Monte Carlo parametrizations that relate the surface energy estimator and the maximum of shower development for both, proton and Iron primaries. Using for each primary their own set of calibration curves, which is of course impossible in practice, we show that the energy could be inferred with a negligible bias and 12% resolution. However, we show that a mixed calibration could also be performed, including both type of primaries, such that the bias still remains low and the achieved resolution is around 15%. In addition, the method allows the simultaneous determination of Xmax in pure surface arrays with resolution better than 7%.