Measurement of the Flux and Zenith-Angle Distribution of Upward Throughgoing Muons by Super-Kamiokande
A total of 614 upward throughgoing muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is [1.74+/-0.07\(stat\)+/-0.02\(sys\)]×10-13 cm-2 s-1 sr-1 compared to an expected flux of [1.97+/-0.44\(theor\)]×10-13 cm-2 s-1 sr-1. The absolute measured flux is in agreement with the prediction within the errors. However, the zenith-angle dependence of the observed upward throughgoing muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the νμ<-->ντ oscillation hypothesis with 22θ>0.4 and 1×10-3<∆m2<1×10-1 eV2 at 90% confidence level.