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This paper reports the first measurement of muon neutrino charged-current interactions without pions in the final state using multiple detectors with correlated energy spectra at T2K. The data was collected on hydrocarbon targets using the off-axis T2K near detector (ND280) and the on-axis T2K near detector (INGRID) with neutrino energy spectra peaked at 0.6 GeV and 1.1 GeV, respectively. The correlated neutrino flux presents an opportunity to reduce the impact of the flux uncertainty and to study the energy dependence of neutrino interactions. The extracted double-differential cross sections are compared to several Monte Carlo neutrino-nucleus interaction event generators showing the agreement between both detectors individually and with the correlated result.

Since its first observation in the 1970s, neutrino-induced neutral-current single positive pion production ($\mathrm{NC}1{\pi }^{+}$) has remained an elusive and poorly understood interaction channel. This process is a significant background in neutrino oscillation experiments and studying it further is critical for the physics program of next-generation accelerator-based neutrino oscillation experiments. In this Letter, we present the first double-differential cross-section measurement of $\mathrm{NC}1{\pi }^{+}$ interactions using data from the ND280 detector of the T2K experiment collected in $\nu$-beam mode. The measured flux-averaged integrated cross section is $\sigma =(6.07\pm 1.22)\times {10}^{-41}{\mathrm{cm}}^2/\text{nucleon}$. We compare the results on a hydrocarbon target to the predictions of several neutrino interaction generators and final-state-interaction models. While model predictions agree with the differential results, the data show a weak preference for a cross-section normalization approximately 30% higher than predicted by most models studied in this Letter.

The T2K Collaboration presents the first measurement of electron neutrino-induced charged-current pion production on a predominantly carbon target in a restricted kinematical phase space. This is performed using data from the 2.5° off-axis near detector, ND280. The differential cross sections with respect to the outgoing electron and pion kinematics, in addition to the total flux-integrated cross section, are obtained. Comparisons between the measured and predicted cross-section results using the neut, genie, and nuwro Monte Carlo event generators are presented. The measured total flux-integrated cross section is $[2.52\pm 0.52(\mathrm{stat})\pm 0.30(\mathrm{syst})]\times {10}^{-39}{\mathrm{cm}}^2{\text{nucleon}}^{-1}$, which is lower than the event generator predictions.

We report a flux-integrated cross section measurement of muon neutrino interactions on water and hydrocarbon via charged current reactions without charged pions in the final state with the WAGASCI-BabyMIND detector, which was installed in the T2K near detector hall in 2018. The detector is located 1.5° off-axis and is exposed to a more energetic neutrino flux than ND280, another T2K near detector, which is located at a different off-axis position. The total flux-integrated cross section is measured to be $1.26\pm 0.18(\text{stat}+\text{syst})\times {10}^{-39}{\mathrm{cm}}^2/\mathrm{nucleon}$ on CH and $1.44\pm 0.21(\text{stat}+\text{syst})\times {10}^{-39}{\mathrm{cm}}^2/\mathrm{nucleon}$ on ${\mathrm{H}}_2\mathrm{O}$. These results are compared to model predictions provided by the neut v5.3.2 and genie v2.8.0 Monte Carlo generators and the measurements are compatible with these models. Differential cross sections in muon momentum and cosine of the muon scattering angle are also reported. This is the first such measurement reported with the WAGASCI-BabyMIND detector and utilizes the 2020 and 2021 datasets.

Muon neutrino and antineutrino disappearance probabilities are identical in the standard three-flavor neutrino oscillation framework, but $CPT$ violation and nonstandard interactions can violate this symmetry. In this work we report the measurements of ${\sin }^2{\theta }_{23}$ and $\mathrm{\Delta }{m}_{32}^2$ independently for neutrinos and antineutrinos. The aforementioned symmetry violation would manifest as an inconsistency in the neutrino and antineutrino oscillation parameters. The analysis discussed here uses a total of $1.97\times {10}^{21}$ and $1.63\times {10}^{21}$ protons on target taken with a neutrino and antineutrino beam respectively, and benefits from improved flux and cross section models, new near-detector samples and more than double the data reducing the overall uncertainty of the result. No significant deviation is observed, consistent with the standard neutrino oscillation picture.

We report an updated measurement of the ${\nu }_{\mu }$-induced, and the first measurement of the ${\overline{\nu }}_{\mu }$-induced coherent charged pion production cross section on ${}^{12}\mathrm{C}$ nuclei in the Tokai-to-Kamioka experiment. This is measured in a restricted region of the final-state phase space for which $p_{\mu ,\pi }>0.2\mathrm{GeV}$, $\cos ({\theta }_{\mu })>0.8$ and $\cos ({\theta }_{\pi })>0.6$, and at a mean (anti)neutrino energy of 0.85 GeV using the T2K near detector. The measured ${\nu }_{\mu }$ charged current coherent pion production flux-averaged cross section on ${}^{12}\mathrm{C}$ is $(2.98\pm 0.37(\mathrm{stat})\pm 0.31(\mathrm{syst}{)}_{-0.00}^{+0.49}({\mathrm{Q}}^2\text{model}))\times {10}^{-40}{\mathrm{cm}}^2$. The new measurement of the ${\overline{\nu }}_{\mu }$-induced cross section on ${}^{12}\mathrm{C}$ is $(3.05\pm 0.71(\mathrm{stat})\pm 0.39(\mathrm{syst}{)}_{-0.00}^{+0.74}({\mathrm{Q}}^2\text{model}))\times {10}^{-40}{\mathrm{cm}}^2$. The results are compatible with both the NEUT 5.4.0 Berger-Sehgal (2009) and GENIE 2.8.0 Rein-Sehgal (2007) model predictions.

This article presents a study of single ${\pi }^{+}$ production in neutrino neutral-current interactions ($\mathrm{NC}1{\pi }^{+}$) using the FGD1 hydrocarbon target of the ND280 detector of the T2K experiment. We report the largest sample of such events selected by any experiment, providing the first new data for this channel in over four decades and the first using a sub-GeV neutrino flux. The signal selection strategy and its performance are detailed together with validations of a robust cross section extraction methodology. The measured flux-averaged integrated cross-section is $\sigma =(6.07\pm 1.22)\times {10}^{-41}{\mathrm{cm}}^2/\mathrm{nucleon}$, $1.3\sigma$ above the NEUT v5.4.0 expectation.

We report the first measurement of neutron capture multiplicity in neutrino-oxygen neutral-current quasielasticlike interactions at the gadolinium-loaded Super-Kamiokande detector using the T2K neutrino beam, which has a peak energy of about 0.6 GeV. A total of 30 neutral-current quasielasticlike event candidates were selected from T2K data corresponding to an exposure of $1.76\times {10}^{20}$ protons on target. The $\gamma$ ray signals resulting from neutron captures were identified using a neural network. The flux-averaged mean neutron capture multiplicity was measured to be ${1.37\pm 0.33(\mathrm{stat}.)}_{-0.27}^{+0.17}(\mathrm{syst}.)$, which is compatible within 2.3 sigma than predictions obtained using our nominal simulation. We discuss potential sources of systematic uncertainty in the prediction and demonstrate that a significant portion of this discrepancy arises from the modeling of hadron-nucleus interactions in the detector medium.

The Super-Kamiokande and T2K Collaborations present a joint measurement of neutrino oscillation parameters from their atmospheric and beam neutrino data. It uses a common interaction model for events overlapping in neutrino energy and correlated detector systematic uncertainties between the two datasets, which are found to be compatible. Using 3244.4 days of atmospheric data and a beam exposure of $19.7(16.3)\times {10}^{20}$ protons on target in (anti)neutrino mode, the analysis finds a $1.9\sigma$ exclusion of $CP$ conservation (defined as $J_{CP}=0$) and a $1.2\sigma$ exclusion of the inverted mass ordering.

We have made improved measurements of three-flavor neutrino mixing with $19.7(16.3)\times {10}^{20}$ protons on target in (anti-)neutrino-enhanced beam modes. A new sample of muon-neutrino events with tagged pions has been added at the far detector, as well as new proton and photon-tagged samples at the near detector. Significant improvements have been made to the flux and neutrino interaction modeling. T2K data continue to prefer the normal mass ordering and upper octant of ${\sin }^2{\theta }_{23}$ with a near-maximal value of the charge-parity violating phase with best-fit values in the normal ordering of ${\delta }_{\mathrm{CP}}=-{2.18}_{-0.47}^{+1.22}$, ${\sin }^2{\theta }_{23}={0.559}_{-0.078}^{+0.018}$ and $\mathrm{\Delta }{m}_{32}^2=({+2.506}_{-0.052}^{+0.039})\times {10}^{-3}{\mathrm{eV}}^2$.