Study The Large Scale Anisotropy Of Cosmic Rays With ARGO-YBJ And ASγ Experiments

The intensity of Galactic cosmic rays is nearly isotropic because of the mod-ulation in the Milky Way. The amplitude of the anisotropy for TeV energy rangeis in magnitude of0.1%. A stable observation with long term and high precisionanalysis method are necessary for the studies of such subtle anisotropy.This paper introduces a χ2iteration method based on equi-zenith angle toanalyse the large scale anisotropy, including assumption of equi-zenith angle,background estimation, construction and minimized of χ2formula. At the sametime, a inspection about the χ2iteration method’s reliability is given by Montecarlo.The main work of this paper is to analyse large scale anisotropy using theexperiment data of ARGO and ASγ. The”tail-in” and”loss-cone” are obviouslyobserved from the large scale anisotropy in sidereal time by analysing the dataof ARGO experiment both in2008and2009. What’s more, we discover thatthe amplitude of sidereal anisotropy rises at lower energy and then decreases athigher energy when dividing the energy range0.9TeV-23.6TeV into7sections.In monthly analysis, a two dimensional image of completed and clear siderealanisotropy can be observed in every month. In the analysis of each season, theamplitude in summer is large than the others, while the phases in four seasons arenearly the same. Also, the amplitude in the diferent declination between10°-50°are almost the same, however, the amplitude becomes smaller from south tonorth. The anisotropy results of ASγ experiment in the sidereal time are that aexceed region at Ra=275°，a large scattered defciency before Ra=175°, whilethe trend of CG efect still can be observed in solar time.