The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5 $$\sigma $$σ , for all $$\delta _{\mathrm{CP}}$$δ CP values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3 $$\sigma $$σ (5 $$\sigma $$σ ) after an exposure of 5 (10) years, for 50% of all $$\delta _{\mathrm{CP}}$$δ CP values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to $$\sin ^{2} 2\theta _{13}$$sin 2 2 θ 13 to current reactor experiments.

The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of $14.7(7.6)\times {10}^{20}$ protons on target in the neutrino (antineutrino) mode, 89 ${\nu }_e$ candidates and seven anti-${\nu }_e$ candidates are observed, while 67.5 and 9.0 are expected for ${\delta }_{CP}=0$ and normal mass ordering. The obtained $2\sigma$ confidence interval for the $CP$-violating phase, ${\delta }_{CP}$, does not include the $CP$-conserving cases (${\delta }_{CP}=0$, $\pi$). The best-fit values of other parameters are ${\sin }^2{\theta }_{23}=0.526_{-0.036}^{+0.032}$ and $\mathrm{\Delta }{m}_{32}^2={2.463}_{-0.070}^{+0.071}\times {10}^{-3}{\mathrm{eV}}^2/c^4$.

This paper reports on the search for heavy neutrinos with masses in the range $140<M_N<493\mathrm{MeV}/{\mathrm{c}}^2$ using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are $N\to {\ell }_{\alpha }^{\pm }{\pi }^{\mp }$ and $N\to {\ell }_{\alpha }^{+}{\ell }_{\beta }^{-}\stackrel{(-)}{\nu }(\alpha ,\beta =e,\mu )$. A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavored currents ($U_e^2$, $U_{\mu }^2$, $U_{\tau }^2$) as a function of the heavy neutrino mass, e.g., $U_e^2<{10}^{-9}$ at 90% C.L. for a mass of $390\mathrm{MeV}/{\mathrm{c}}^2$. These constraints are competitive with previous experiments.

The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearance and disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a pion decay has been tagged is added to the four single-ring samples used in previous T2K oscillation analyses. Through combined analyses of these five samples, simultaneous measurements of four oscillation parameters, $|\mathrm{\Delta }{m}_{32}^2|$, ${\sin }^2{\theta }_{23}$, ${\sin }^2{\theta }_{13}$, and ${\delta }_{\mathrm{CP}}$ and of the mass ordering are made. A set of studies of simulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interaction model uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals are presented for combinations of the oscillation parameters with and without the inclusion of reactor constraints on ${\sin }^2{\theta }_{13}$. When combined with reactor measurements, the hypothesis of $CP$ conservation (${\delta }_{\mathrm{CP}}=0$ or $\pi$) is excluded at 90% confidence level. The 90% confidence region for ${\delta }_{\mathrm{CP}}$ is $[-2.95,-0.44]$ ($[-1.47,-1.27]$) for normal (inverted) ordering. The central values and 68% confidence intervals for the other oscillation parameters for normal (inverted) ordering are $\mathrm{\Delta }{m}_{32}^2=2.54\pm 0.08(2.51\pm 0.08)\times {10}^{-3}{\mathrm{eV}}^2/c^4$ and ${\sin }^2{\theta }_{23}=0.55_{-0.09}^{+0.05}$ ($0.55_{-0.08}^{+0.05}$), compatible with maximal mixing. In the Bayesian analysis, the data weakly prefer normal ordering (Bayes factor 3.7) and the upper octant for ${\sin }^2{\theta }_{23}$ (Bayes factor 2.4).