1998/08/03 by G. L. Fogli, E. Lisi, A. Marrone +2 · 9 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Neutrino Physics Research #Particle physics theoretical and experimental studies #hep-ph
paper · pdf · doi:10.1103/physrevd.59.033001
published as Phys.Rev.D59:033001,1999 · 35 pages (RevTeX), including 20 ps figures (with epsfig.sty)
arxiv created 1998/08/03 · openalex publication_date 1998/12/22 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present a detailed analysis of the zenith angle distributions of atmospheric neutrino events observed in the Super-Kamiokande (SK) underground experiment, assuming two-flavor and three-flavor oscillations (with one dominant mass scale) among active neutrinos. In particular, we calculate the five angular distributions associated with sub-GeV and multi-GeV \ensuremathμ-like and e-like events and to upward through-going muons, for a total of 30 accurately computed observables (zenith bins). First we study how such observables vary with the oscillation parameters, and then we perform a fit to the experimental data as measured in SK for an exposure of 33 kTy (535 days). In the two-flavor mixing case, we confirm the results of the SK Collaboration analysis, namely, that \ensuremathν_\ensuremathμ\ensuremath↔\ensuremathν_\ensuremathτ oscillations are preferred over \ensuremathν_\ensuremathμ\ensuremath↔\ensuremathνe, and that the no oscillation case is excluded with high confidence. In the three-flavor mixing case, we perform our analysis with and without the additional constraints imposed by the CHOOZ reactor experiment. In both cases, the analysis favors a dominance of the \ensuremathν_\ensuremathμ\ensuremath↔\ensuremathν_\ensuremathτ channel. Without the CHOOZ constraints, the amplitudes of the subdominant \ensuremathν_\ensuremathμ\ensuremath↔\ensuremathνe and \ensuremathνe\ensuremath↔\ensuremathν_\ensuremathτ transitions can also be relatively large, indicating that, at present, current SK data do not exclude sizable \ensuremathνe mixing by themselves. After combining the CHOOZ and SK data, the amplitudes of the subdominant transitions are constrained to be smaller, but they can still play a non-negligible role both in atmospheric and other neutrino oscillation searches. In particular, we find that the \ensuremathνe appearance probability expected in long baseline experiments can reach the testable level of \ensuremath∼15%. We also discuss Earth matter effects, theoretical uncertainties, and various aspects of the statistical analysis.