Precise Measurement of the Neutrino Mixing Parameter θ23 from Muon Neutrino Disappearance in an Off-axis Beam

March 7, 2014

New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter θ23. Marginalizing over the values of other oscillation parameters yields sin223) = 0.514 +0.055-0.056 (0.511 ± 0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Δm232 = 2.51 ± 0.10 × 10-3 eV2/c4 (inverted hierarchy: Δm213 = 2.48 ± 0.10 × 10-3 eV2/c4). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty.