Author: M.D. Messier for the Super--Kamiokande Collaboration
Title: Atmospheric Neutrinos in Super--Kamiokande
Abstract: Since the initial announcement of evidence for oscillations of atmosphericneutrinos, Super--Kamiokande has increased its atmospheric neutrino sample by40% to 45.3 kiloton-years of fully-contained interactions and 42.2kiloton-years of partially-contained interactions. The data exhibitsignificantly low values of R (= (mu/e)_DATA/(mu/e)_MC) in both the sub-GeVsample (R = 0.67 +/- 0.02 +/- 0.05) and multi-GeV sample (R = 0.66 +/- 0.04+/- 0.08) due to a zenith-angle dependent deficit of muon neutrino inducedevents. The observed deficits cannot be explained by any combination of knownsystematic uncertainties but are consistent with neutrino oscillations ofnu_mu to nu_tau with sin^2(2theta) > 0.86 and 1x10^-3 < Delta m^2 < 8x10^-3eV^2. The data are also well fit by oscillations of nu_mu to nu_sterile withsin^2(2theta) > 0.87 and 2x10^-3 < Delta m^2 < 7x10^-3 eV^2. With the currentsample, these two oscillation modes cannot be distinguished.
Comments: 6 pages, Latex with revtek.sty, 6 .eps figures included using epsf.sty Report-no:Subj-class: hep-exJournal-ref: