Super-Kamiokande atmospheric neutrinos

Results on atmospheric neutrino analysis at Super-Kamiokande I is presented. The whole data set of atmospheric neutrino sample in Super-Kamiokande I is consistently explained with an assumption of pure νμ-ντ oscillations. The allowed range of parameters is 1.5×10−3<Δm2<3.4×10−3 eV2 and sin22θ>0.92 at 90% C.L. In the oscillation analysis, we improved the treatment of systematic errors so that they can be considered as independent. This makes possible to find which systematic errors have larger effect on the analysis results. Some sensitivity studies under several assumptions of improvements in systematic errors are presented.