Measurement of Atmospheric Neutrino Oscillations with IceCube/DeepCore in its 79-string Configuration

Abstract

With its low-energy extension DeepCore, the IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station is able to detect neutrino events with energies as low as 10GeV. This permits the investigation of flavor oscillations of atmospheric muon neutrinos in an energy range not covered by other experiments, opening a new window on the physics of atmospheric neutrino oscillations. The oscillation probability depends on the observed neutrino zenith angle and energy. Maximum disappearance is expected for vertically upward moving muon neutrinos at around 25GeV. A recent analysis has rejected the non-oscillation hypothesis with a significance of about 5 σ based on data obtained with IceCube while it was operating in its 79-string configuration [1]. The analysis presented here uses data from the same detector configuration, but implements a more powerful approach for the event selection, which yields a dataset with an order of magnitude higher statistics (more than 8 000 events). We present new results based on a likelihood analysis of the two observables zenith angle and energy. The non-oscillation hypothesis is rejected with a significance32 of about 5.7 σ. In the 2-flavor approximation, our best-fit oscillation parameters are Δm2 = (2.2 ± 0.5) · 10−3eV2 and0.14 sin2 (2θ23) = 1.0+0-0.14, in good agreement with measurements at lower energy.