We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor νμ<-->ντ oscillations with 22θ>0.82 and 5×10-4<∆m2<6×10-3 eV 2 at 90% confidence level.
- Physical Review Letters
- Pub Date:
- August 1998
- High Energy Physics - Experiment
- 9 pages (two-column) with 4 figures. Small corrections to Eqn.4 and Fig.3. Final version to appear in PRL