ZENITH DISTRIBUTION OF ATMOSPHERIC NEUTRINO EVENTS AND ELECTRON NEUTRINO MIXING

Assuming atmospheric neutrino oscillations with dominant nu(mu)<->nu(t au) transitions, we discuss how subdominant nu(e) mixing (within the C hooz reactor bounds) can alter the zenith distributions of neutrino-in duced electrons and muons. We isolate two peculiar distortion effects, one mainly related to nu(e) mixing in vacuum and the other matter to oscillations, that may be sufficiently large to be detected by the Sup erKamiokande atmospheric nu experiment. These effects (absent for pure two-flavor nu(mu)<->nu(tau) transitions) do not vanish in the limit o f energy-averaged oscillations. (C) 1998 Published by Elsevier Science B.V. All rights reserved.