Measurement of the tau neutrino cross section in atmospheric neutrino oscillations with Super-Kamiokande

Using 5326 days of atmospheric neutrino data, a search for atmospheric tau neutrino appearance has been performed in the Super-Kamiokande experiment. Super-Kamiokande measures the tau normalization to be 1.47 ± 0.32 under the assumption of normal neutrino hierarchy, relative to the expectation of unity with neutrino oscillation. The result excludes the hypothesis of no-tau appearance with a significance level of 4.6σ. The inclusive charged-current tau neutrino cross section averaged by the tau neutrino flux at SuperKamiokande is measured to be ð0.94 ± 0.20Þ × 10−38 cm2. The measurement is consistent with the Standard Model prediction, agreeing to within 1.5σ.