Studies of the Time Structure of Extended Air Showers for Direction Reconstruction with the HAWC Outrigger Array

TL;DR

This paper presents a Monte Carlo-based model of the air shower time structure for the HAWC observatory's outrigger array, enhancing direction reconstruction accuracy for high-energy gamma-ray detection.

Contribution

It introduces a new model of the shower front tailored for the HAWC outrigger array, improving shower parameter estimation and direction reconstruction.

Findings

Model improves accuracy of shower direction reconstruction.

Enhanced understanding of shower front timing structure.

Demonstrates benefits of extended array for high-energy gamma-ray detection.

Abstract

The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is a ground-based air shower array designed to detect Cherenkov light produced in water by secondary particles from atmospheric air showers. In order to improve the sensitivity at the highest energies, especially for the shower cores falling outside the main array, 345 smaller Water Cherenkov Detectors (WCDs) were installed around the main array, the outrigger array. This extension increased the instrumented area of HAWC by a factor of four. With the increased size of the array, and the ability to detect shower particles further away from the core, understanding of the time structure of the shower front is crucial for accurate direction reconstruction and mandates proper modeling. In this contribution, we present a model of the shower front as expected to be observed by the outriggers obtained from Monte-Carlo simulations. Applying this model to shower reconstruction, the improvements on air shower parameter are studied.