On Shadow of the Moon in Extensive Air Shower Data.pdf

a r X i v : 0 7 0 6 .1 4 4 1 v 2 [ a s t r o - p h ] 2 4 F e b 2 0 0 8 Astronomy Astrophysics manuscript no. (will be inserted by hand later) On Shadow of the Moon in Extensive Air Shower Data F. Sheidaeib,?, A. Anvaria,b,??, M. Bahmanabadia,b,???, and M. Khakian Ghomia,? J. Samimia,b,? a) ALBORZ Observatory, Sharif University of Technology, Tehran, Iran. b) Department of physics, Sharif University of Technology, P.O.Box 11365- 9161,Tehran, Iran. the date of receipt and acceptance should be inserted later Abstract. A new technique has been devised for the analysis of extensive air shower data in observing the effect of the moon on 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 Nsky 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× 105 EAS events recorded at Alborz observatory. Key words. Cosmic Ray, Extensive Air Shower, Angular resolution. 1. Introduction In 1957, Clark (Clark 1975) recognized that the moon and the sun cast a shadow in the isotropic flux of cosmic-ray nuclei. As they pass overhead during a transit, the moon Send offprint requests to: F. Sheidaei ? e-mail: sheydaei@sharif.ir ?? e-mail: anvari@sharif.ir ??? e-mail: bahmanabadi@sharif.ir ? e-mail: khakian@sharif.ir ? e-mail: samimi@sharif.ir 2 F. Sheidaei et al.: On Shadow of the Moon in Extensive Air Shower Data and the sun block cosmic rays, so their shadows in the cosmic ray flux shoul