Measurement of Neutrino Oscillation Parameters from Muon Neutrino Disappearance with an Off Axis Beam

OpenAlex İngilizce

The T2K Collaboration reports a precision measurement of muon neutrino disappearance with an off-axis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The Super-Kamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to $3.01\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target. In the absence of neutrino oscillations, $205\ifmmode\pm\else\textpm\fi{}17$ (syst) events are expected to be detected while only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum, assuming three neutrino flavors and normal mass hierarchy yields a best-fit mixing angle ${sin}^{2}({\ensuremath{\theta}}_{23})=0.514\ifmmode\pm\else\textpm\fi{}0.082$ and mass splitting $|\ensuremath{\Delta}{m}_{32}^{2}|={2.44}_{\ensuremath{-}0.15}^{+0.17}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{eV}}^{2}/{c}^{4}$. Our result corresponds to the maximal oscillation disappearance probability.