Moon and Sun Shadowing Observed by the MACRO Detector

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.