We report measurements by the T2K experiment of the parameters $theta_{23}$ and $Delta m^2_{32}$ which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2Ks 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 $1.49 times 10^{21}$ protons on target (POT) in neutrino mode and $1.64 times 10^{21}$ POT in antineutrino mode are used. The best-fit values obtained by T2K were $sin^2left(theta_{23}right)=0.51^{+0.06}_{-0.07} left(0.43^{+0.21}_{-0.05}right)$ and $Delta m^2_{32}=2.47^{+0.08}_{-0.09} left(2.50^{+0.18}_{-0.13}right)$evmass 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 non-physical 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.
تحميل البحث