The Mercedes water Cherenkov detector

TL;DR

This paper introduces a compact, cost-effective water Cherenkov detector design with machine learning-based analysis for gamma-ray and cosmic ray detection, suitable for large-scale high-altitude observatories.

Contribution

It presents a novel small, single-layer water Cherenkov detector concept with adjustable PMT placement, demonstrating technical feasibility and potential for large-scale gamma-ray observatories.

Findings

Effective gamma/hadron discrimination using machine learning techniques.

Cost-efficient and flexible detector design suitable for high-altitude deployment.

Sensitivity to low energy EAS particles demonstrated in various configurations.

Abstract

The concept of a small, single-layer water Cherenkov detector, with three photomultiplier tubes (PMTs), placed at its bottom in a $120^{\circ}$ star configuration (\emph{Mercedes} Water Cherenkov Detector) is presented. The PMTs are placed near the lateral walls of the stations with an adjustable inclination and may be installed inside or outside the water volume. To illustrate the technical viability of this concept and obtain a first-order estimation of its cost, an engineering design was elaborated. The sensitivity of these stations to low energy Extensive Air Shower (EAS) electrons, photons and muons is discussed, both in compact and sparse array configurations. It is shown that the analysis of the intensity and time patterns of the PMT signals, using machine learning techniques, enables the tagging of muons, achieving an excellent gamma/hadron discrimination for TeV showers. This concept minimises the station production and maintenance costs, allowing for a highly flexible and fast installation. Mercedes Water Cherenkov Detectors (WCDs) are thus well-suited for use in high-altitude large gamma-ray observatories covering an extended energy range from the low energies, closing the gap between satellite and ground-based measurements, to very high energy regions, beyond the PeV scale.