On the interpretation of the atmospheric neutrino data in terms of flavor changing neutrino interactions

Flavour changing (FC) neutrino-matter interactions have been proposed as a solution to the atmospheric neutrino anomaly. Here we perform the analysis of the full set of the recent 52 kTy Super-Kamiokande atmospheric neutrino data, including the zenith angle distribution of the contained events as we ll as the higher energy upward-going stopping and through-going muon events . Our results show that the FC mechanism can describe the full data sample with a chi (2)(min) = 44/33 d.o.f. which is acceptable only at the 90.5% co nfidence level, while the nu (mu) --> nu (tau) oscillation scenario gives a chi (min)2 = 23.5/33 d.o.f. which is valid at the 11% CL. The combined ana lysis confines the amount of FC to be either close to maximal or to the lev el of about (10-50)%.