The cosmic ray shadow of the Moon observed with the ANTARES neutrino telescope

TL;DR

This paper demonstrates the ANTARES neutrino telescope's ability to accurately determine its pointing direction by observing the Moon's shadow in atmospheric muon flux, confirming its angular resolution and pointing accuracy.

Contribution

It provides the first measurement of the Moon shadow with ANTARES, validating the detector's angular resolution and pointing performance using cosmic ray absorption effects.

Findings

Moon shadow observed with 3.5σ significance

Angular resolution for muons is 0.73° ± 0.14°

Pointing accuracy is consistent with expectations

Abstract

One of the main objectives of the ANTARES telescope is the search for point-like neutrino sources. Both the pointing accuracy and the angular resolution of the detector are important in this context and a reliable way to evaluate this performance is needed. In order to measure the pointing accuracy of the detector, one possibility is to study the shadow of the Moon, i.e. the deficit of the atmospheric muon flux from the direction of the Moon induced by the absorption of cosmic rays. Analysing the data taken between 2007 and 2016, the Moon shadow is observed with $3.5\sigma$ statistical significance. The detector angular resolution for downward-going muons is 0.73$^{\circ}\pm0.14^{\circ}.$ The resulting pointing performance is consistent with the expectations. An independent check of the telescope pointing accuracy is realised with the data collected by a shower array detector onboard of a ship temporarily moving around the ANTARES location.