Observation of the Shadowing of Cosmic Rays by the Moon using a Deep Underground Detector

TL;DR

This paper reports the first underground detection of the moon's shadow in cosmic rays using the MACRO detector, confirming its angular resolution and pointing accuracy through a maximum-likelihood analysis.

Contribution

It provides the first evidence of lunar shadowing in cosmic rays with an underground detector and quantifies the detector's angular resolution and pointing capabilities.

Findings

Detected moon shadow with 3.6 sigma significance

Angular resolution of 0.9+/-0.3 degrees

Confirmed MACRO's pointing accuracy

Abstract

Using data collected by the MACRO experiment during the years 1989-1996, we show evidence for the shadow of the moon in the underground cosmic ray flux with a significance of 3.6 sigma. This detection of the shadowing effect is the first by an underground detector. A maximum-likelihood analysis is used to determine that the angular resolution of the apparatus is 0.9+/-0.3 degrees. These results demonstrate MACRO's capabilities as a muon telescope by confirming its absolute pointing ability and quantifying its angular resolution.