Moon and Sun Shadowing Observed by the MACRO Detector

TL;DR

This study used the MACRO detector to observe the Moon and Sun shadows in muon data, confirming cosmic ray interactions and magnetic deflections with high statistical significance.

Contribution

First observation of Moon and Sun shadows in underground muon data with detailed analysis of magnetic deflections at TeV energies.

Findings

Moon shadow detected with >5 sigma significance

Sun shadow detected with ~4 sigma significance

Sun shadow displaced by 0.6 degrees due to magnetic deflection

Abstract

Using over 40 million muons collected since 1989 by the MACRO detector we have searched for a depletion of muons coming from the direction of the Moon due to primary cosmic rays striking the Moon. We observe this Moon shadow in the expected position with a statistical significance of more than 5 standard deviations. We have analyzed the same data for an analogous Sun shadow, and have found a signal with a significance of about 4 standard deviations. The Sun shadow is displaced from the Sun's position by about 0.6 degrees North in ecliptic coordinates. This displacement is compatible with a deflection of primary cosmic rays due to the Interplanetary Magnetic Field in the 10-20 TeV primary energy range which is relevant to the underground muons observed by MACRO.