Moon shadow on high energy cosmic ray in data of a small extensive air shower array

Abstract

Data from a small air shower array were used to examine the cosmic ray shadow of the Moon at energies more than 100 TeV. A simple technique has been used for the analysis of this data. In this technique the number of EAS events with arrival directions falling in error circles centered about the moving moon is compared to the mean number of events falling in error circles with centers randomly chosen in the sky. For any assumed angular radius of the error circle the deficit in EAS event count in the direction of moon which is a moon-related effect is interpreted as the shadow of the moon. A simple theoretical model has been developed to relate the mean number of EAS events, N sky , to the angular radius of the error circle and has been applied to the counts from the moon’s direction in order to extract the physical parameters of the shadow of the moon. The technique and the theoretical model has been used on 1.7 × 10 5 EAS events recorded by a small air shower array.