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.
arXiv preprint: https://arxiv.org/abs/2303.14228
DOI: https://doi.org/10.1103/PhysRevD.108.112009
Data release: https://doi.org/10.5281/zenodo.13306653
This paper reports the T2K measured muon-neutrino and muon-antineutrino-induced charged current coherent pion production flux-averaged cross section on carbon-12 within a restricted kinematic phase-space. The results are compatible with both the NEUT 5.4.0 Berger-Sehgal (2009) and GENIE 2.8.0 Rein-Sehgal (2007) model predictions.
The T2K muon-neutrino (left) and muon-antineutrino (right) CC-COH cross section measurement on C assuming F(A) = A^(1/3).
The Super-Kamiokande and T2K collaborations present a joint measurement of neutrino oscillation parameters from their atmospheric and beam neutrino data. A common neutrino interaction model has been developed for the events of the two experiments which overlap in energy, and correlations between their detector systematic uncertainties were evaluated. Using 3244.4 days of atmospheric data and a beam exposure of respectively 19.7E20 and 16.3E20 protons on target in neutrino and antineutrino running modes, we find an exclusion of the CP-conserving value of the Jarlskog invariant with a significance varying between 1.9σ and 2.0σ depending on the analysis considered, a limited preference for the normal mass ordering (MO), and no strong preference for the θ23 octant.
https://arxiv.org/abs/2305.09916Muon neutrino and antineutrino disappearance probabilities are identical in the standard three-flavor neutrino oscillation framework, but CPT violation and non-standard interactions can violate this symmetry. In this work we report the measurements of sin2θ23 and Δm232 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 1.97E21 and 1.63E21 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.
The T2K experiment presents new constraints on the neutrino oscillation parameters, using 3.6E21 protons on target (POT). The results include world-leading constraints on the CP-violating phase, delta CP, the Jarlskog invariant, and the atmospheric oscillation parameters.
This analysis increases the data at the far detector by 4.7E20 POT neutrino data on the previous result, and sees significant improvements to the analysis methodology. The near-detector analysis includes more than double the data, and uses new selections. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE hadron scattering data on a replica of the T2K target to tune the neutrino flux model, leading to a reduction of flux uncertainties from 9% to 5% in the neutrino flux peak. The neutrino interaction model was also improved to include new nuclear effects and calculations.
The normal ordering and upper octant is favoured, with a nearly maximally CP violating phase, consistent with previous results. The analysis excludes delta CP=0 and pi at more than 90% confidence level. It also excludes a Jarlskog invariant of zero at more than 2 sigma credible level with a flat prior in delta CP, and just below 2 sigma using a flat prior in sin delta CP. Furthermore, the analysis finds a sin^2 theta_{13} consistent with the reactor experiments.
The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2\% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator.
Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.
We report measurements of the flux-integrated |νμ-bar| and |νμ-bar+νμ| charged-current cross-sections on water and hydrocarbon targets using the T2K anti-neutrino beam with a mean beam energy of 0.86 GeV. The signal is defined as the (anti-)neutrino charged-current interaction with one induced |μ±| and no detected charged pion or proton. These measurements are performed using a new WAGASCI module recently added to the T2K setup in combination with the INGRID Proton Module.
arXiv preprint: https://arxiv.org/abs/2004.13989
DOI: https://doi.org/10.1093/ptep/ptab014
Reference: PTEP 2021 (2021) 4, 043C01
Data release: https://doi.org/10.5281/zenodo.7065209
The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of 14.9(16.4)×10E20 protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the Pontecorvo-Maki-Nakagawa-Sakata parameters. For fits including a constraint on sin2θ13 from reactor data and assuming normal mass ordering T2K measures sin2θ23=0.53-0.04+0.03 and Δm322=(2.45±0.07)×10-3 eV2 c-4. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper sin2θ23 octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the 2σ level.
This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-π+ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single-π+ and at least one proton in the final state, at the ND280 off-axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models which have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions.
A representative figure would be the cross-section plot of the pN variable as attached.
arXiv preprint: https://arxiv.org/abs/2102.03346
DOI: https://doi.org/10.1103/PhysRevD.103.112009
Reference: Phys.Rev.D 103 (2021) 11, 112009
Data release: https://t2k-experiment.org/results/2021_tki_numucc1pinp/
