Observation of the Galactic Cosmic Ray Moon shadowing effect with the ARGO-YBJ experiment

TL;DR

This paper reports the observation of the Moon shadow effect caused by galactic cosmic rays using the ARGO-YBJ detector, demonstrating its capability to calibrate energy, measure angular resolution, and verify detector pointing accuracy.

Contribution

First observation of the galactic cosmic ray Moon shadow with ARGO-YBJ, validating detector performance and calibration methods at multi-TeV energies.

Findings

Angular resolution matches simulations

Moon shadow displacement calibrates energy scale

Detector pointing accuracy confirmed

Abstract

Cosmic rays are hampered by the Moon and a deficit in its direction is expected (the so-called Moon shadow). The Moon shadow is an important method to determine the performance of an air shower array. In fact, the westward displacement of the shadow centre, due to the propagation of cosmic rays in the geomagnetic field, allows to calibrate the energy scale of the primary particles observed by the detector. In addition, the shape of the shadow allows a measurement of the angular resolution and the position of the deficit at high energy allows the evaluation of the pointing accuracy of the detector. In this paper we present the observation of the galactic cosmic rays Moon shadowing effect performed by the ARGO-YBJ experiment in the multi-TeV energy region. The measured angular resolution as a function of the shower size is compared with the expectations from a MC simulation.