We report measurements by the T2K experiment of the parameters θ23 and Δm322, which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K's neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from 1.49×1021 protons on target (POT) in neutrino mode and 1.64×1021 POT in antineutrino mode are used. The best-fit values obtained by T2K were sin2(θ23)=0.51-0.07+0.06(0.43-0.05+0.21) and Δm322=2.47-0.09+0.08(2.50-0.13+0.18)×10-3 eV2/c4 for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take nonphysical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.
Publication Source (Journal or Book title)
Physical Review D
Abe, K., Akhlaq, N., Akutsu, R., Ali, A., Alt, C., Andreopoulos, C., Antonova, M., Aoki, S., Arihara, T., Asada, Y., Ashida, Y., Atkin, E., Awataguchi, Y., Barker, G., Barr, G., Barrow, D., Batkiewicz-Kwasniak, M., Beloshapkin, A., Bench, F., Berardi, V., Berns, L., Bhadra, S., Blondel, A., Bolognesi, S., Bonus, T., Bourguille, B., Boyd, S., & Bravar, A. (2021). T2K measurements of muon neutrino and antineutrino disappearance using 3.13×1021 protons on target. Physical Review D, 103 (1) https://doi.org/10.1103/PhysRevD.103.L011101