Atmospheric neutrinos: LMA oscillations, Ue3 induced interference and CP-violation Original Research Article

We consider oscillations of the low energy (sub-GeV sample) atmospheric neutrinos in the three neutrino context. We present the semi-analytic study of the neutrino evolution and calculate characteristics of the e-like events (total number, energy spectra and zenith angle distributions) in the presence of oscillations. At low energies there are three different contributions to the number of events: the LMA contribution (from νe-oscillations driven by the solar oscillation parameters), the Ue3-contribution proportional to s132, and the Ue3-induced interference of the two amplitudes driven by the solar oscillation parameters. The interference term is sensitive to the CP-violation phase. We describe in details properties of these contributions. We find that the LMA, the interference and Ue3 contributions can reach 5–6%, 2–3% and 1–2% correspondingly. An existence of the significant (>3–5%) excess of the e-like events in the sub-GeV sample and the absence of the excess in the multi-GeV range testifies for deviation of the 2–3 mixing from maximum. We consider a possibility to measure the deviation as well as the CP-violation phase in future atmospheric neutrino studies.