Updated Global Analysis of the Atmospheric Neutrino Data in terms of neutrino oscillations

Abstract

A global analysis of all the available atmospheric neutrino data is presented in terms of neutrino oscillations in the nu_mu -> nu_tau and nu_mu -> nu_s channels, where nu_s denotes a sterile neutrino. We perform our analysis of the contained events data as well as the upward-going neutrino-induced muon fluxes. In addition to the previous data samples of Frejus, Nusex, IMB and Kamioka experiments, we include the full data set of the 52 kton-yr of Super-Kamiokande, the recent 4.6 kton-yr contained events of Soudan2 and the results on upgoing muons from the MACRO and Baksan detectors. From the statistical analysis it emerges that the nu_mu -> nu_tau channel provides the best agreement with the combined data, with a best fit point of sin^2(2 theta) = 0.99 and Delta m^2 = 3.0 * 10^{-3} eV^2. Although somehow disfavoured, the nu_mu -> nu_s channels cannot be ruled out on the basis of the global fit to the full set of observables.