Tau neutrino appearance via neutrino oscillations in atmospheric neutrinos.

摘要

A search for the appearance of tau neutrinos from numu ↔ nu tau oscillations in the atmospheric neutrinos has been conducted using the atmospheric neutrino data from the Super-Kamiokande-I and the Super-Kamiokande-II experiment. A tau neutrino enriched event sample is selected by using the event topologies of the decay of tau leptons produced in charged-current weak interactions. An excess of tau neutrino signals is observed, and a best-fit tau neutrino appearance signal of 162 +/- 59 (stat.) +21-56 (sys.), which disfavors the no tau neutrino appearance hypothesis by 2.1 sigma. This is consistent with the expected number of tau neutrino events, 121 +/- 39 (sys.) for Deltam2 = 2.4 x 10-3eV2, assuming the full mixing in numu ↔ nutau oscillations. The Super-Kamiokande atmospheric neutrino data are consistent with tau neutrino appearance from numu ↔ nutau oscillations.