Evaluation of a wide-sky survey method for EAS experiments

Several ground-based extensive air shower (EAS) experiments such as As γ   and Milagro have observed that CRs show large scale anisotropy in the TeV energy region with an amplitude of about 0.1%. The amplitude of anisotropy is so weak that we have to deal carefully with potential errors introduced by analysis methods. In this paper, we discuss a method based on χ2χ2-iteration algorithm for wide sky survey analysis in the use of equi-zenith angle method with large sample data. The results show that χ2χ2-iteration method leads to accurate and reasonable results in the case of large scale anisotropy in data samples.

► Anisotropy given by equi-zenith angle method is far from being accurate. ► χ2χ2 Iteration technique is found to give accurate results with expectation. ► Azimuth modification will not introduce “false” anisotropy phenomenon.