Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam

T2K Collaboration, K. Abe, Francesca Bay, Silvestro Di Luise, S. Horikawa, S. Murphy, André Rubbia, Davide Sgalaberna, Et Al.
T2K reports its first measurements of the parameters governing the disappearance ofν μ in an off-axis beam due to flavor change induced by neutrino oscillations. The quasimonochromaticν μ beam, produced with a peak energy of 0.6 GeV at J-PARC, is observed at the far detector Super-Kamiokande, 295 km away, where theν μ survival probability is expected to be minimal. Using a data set corresponding to 4.01 × 10 20 protons on target, 34 fully contained μ-like events were observed. The best-fit
more » ... . The best-fit oscillation parameters are sin 2 ðθ 23 Þ ¼ 0.45 and jΔm 2 32 j ¼ 2.51 × 10 −3 eV 2 with 68% confidence intervals of 0.38-0.64 and 2.26-2.80 × 10 −3 eV 2 , respectively. These results are in agreement with existing antineutrino parameter measurements and also with the ν μ disappearance parameters measured by T2K.
doi:10.3929/ethz-b-000118772 fatcat:4lq7bmav6bcsbf7xszfdb3q2mu