First measurement of the νμ charged-current cross section without pions in the final state on a water target
We report the first differential measurement of the charged-current interaction cross section of νμ on water with no pions in the final state. This flux-averaged measurement has been made using the T2K experiment’s off-axis near detector, and is reported in doubly-differential bins of muon momentum and angle. The flux-averaged total cross section in a restricted region of phase space was found to be σ=(0.95±0.13)×10−38cm2 per n.
We report the first measurement of the flux-averaged cross section for charged current coherent π+ production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al. models.
First Measurement of the Muon Neutrino Charged Current Single Pion Production Cross Section on Water with the T2K Near Detector
The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies ∼0.8~GeV. The differential measurements are presented as a function of muon and pion kinematics, in the restricted phase-space defined by pπ+>200MeV/c, pμ− >200MeV/c, cosθπ+ >0.3 and cosθμ− >0.3. The total flux integrated νμ charged current single positive pion production cross section on water in the restricted phase-space is measured to be ⟨σ⟩ϕ=4.25±0.48 (stat)±1.56 (syst)×10−40 cm2/nucleon. The total cross section is consistent with the NEUT prediction (5.03×10−40 cm2/nucleon) and 2σ lower than the GENIE prediction (7.68×10−40 cm2/nucleon). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but over-estimates the overall cross section normalization.
Measurement of double-differential muon neutrino charged-current interactions on C8H8 without pions in the final state using the T2K off-axis beam
We report the measurement of muon neutrino charged-current interactions on carbon without pions in the final state at the T2K beam energy using 5.734×1020 protons on target. For the first time the measurement is reported as a flux-integrated, double-differential cross-section in muon kinematic variables (cosθμ, pμ), without correcting for events where a pion is produced and then absorbed by final state interactions. Two analyses are performed with different selections, background evaluations and cross-section extraction methods to demonstrate the robustness of the results against biases due to model-dependent assumptions. The measurements compare favorably with recent models which include nucleon-nucleon correlations but, given the present precision, the measurement does not solve the degeneracy between different models. The data also agree with Monte Carlo simulations which use effective parameters that are tuned to external data to describe the nuclear effects. The total cross-section in the full phase space is σ=(0.417±0.047(syst)±0.005(stat))×10−38cm2 nucleon−1 and the cross-section integrated in the region of phase space with largest efficiency and best signal-over-background ratio (cosθμ>0.6 and pμ>200 MeV) is σ=(0.202±0.0359(syst)±0.0026(stat))×10−38cm2 nucleon−1.
Measurement of the muon neutrino inclusive charged-current cross section in the energy range of 1-3 GeV with the T2K INGRID detector
We report a measurement of the νμ-nucleus inclusive charged current cross section (=σcc) on iron using data from exposed to the J-PARC neutrino beam. The detector consists of 14 modules in total, which are spread over a range of off-axis angles from 0° to 1.1°. The variation in the neutrino energy spectrum as a function of the off-axis angle, combined with event topology information, is used to calculate this cross section as a function of neutrino energy. The cross section is measured to be σcc(1.1 GeV)=1.10±0.15 (10−38cm2/nucleon), σcc(2.0 GeV)=2.07±0.27 (10−38cm2/nucleon), and σcc(3.3 GeV)=2.29±0.45 (10−38cm2/nucleon), at energies of 1.1, 2.0, and 3.3 GeV, respectively. These results are consistent with the cross section calculated by the neutrino interaction generators currently used by T2K. More importantly, the method described here opens up a new way to determine the energy dependence of neutrino-nucleus cross sections.
Measurement of the νμ charged current quasi-elastic cross-section on carbon with the T2K on-axis neutrino beam
We report a measurement of the νμ charged current quasi-elastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasi-elastic cross-sections on carbon at mean neutrino energies of 1.94 GeV and 0.93 GeV are (11.95±0.19(stat.)+1.82−1.47(syst.))×10−39cm2/neutron and (10.64±0.37(stat.)+2.03−1.65(syst.))×10−39cm2/neutron, respectively. These results agree well with the predictions of neutrino interaction models. In addition, we investigated the effects of the nuclear model and the multi-nucleon interaction.
The Charged-Current Quasi-Elastic (CCQE) interaction, νl+n→l−+p, is the dominant CC process at Eν∼1 GeV and contributes to the signal in accelerator-based long-baseline neutrino oscillation experiments operating at intermediate neutrino energies. This paper reports a measurement by the T2K experiment of the νμ CCQE cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum (pμ) and angle with respect to the incident neutrino beam (θμ). The flux-integrated CCQE cross section was measured to be (0.83±0.12)×10−38 cm2 in good agreement with NEUT MC value of 0.88×10−38 cm2. The energy dependence of the CCQE cross section is also reported. The axial mass, MAQE, of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shape-only) pμcosθμ distribution, the effective MAQE parameter was measured to be 1.26+0.21−0.18 GeV/c2 (1.43+0.28−0.22 GeV/c2).
Measurement of the inclusive νμ charged current cross section on iron and hydrocarbon in the T2K on-axis neutrino beam
We report a measurement of the νμ inclusive charged current cross sections on iron and hydrocarbon in the T2K on-axis neutrino beam. The measured inclusive charged current cross sections on iron and hydrocarbon averaged over the T2K on-axis flux with a mean neutrino energy of 1.51 GeV are (1.444±0.002(stat.)+0.189−0.157(syst.))×10−38cm2/nucleon, and (1.379±0.009(stat.)+0.178−0.147(syst.))×10−38cm2/nucleon, respectively, and their cross section ratio is 1.047±0.007(stat.)±0.035(syst.). These results agree well with the predictions of neutrino interaction model and thus demonstrate the correct treatment of the nuclear effect for iron and hydrocarbon targets in the model.
Measurement of the Inclusive Electron Neutrino Charged Current Cross Section on Carbon with the T2K Near Detector
The T2K off-axis near detector, ND280, is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies ∼1 GeV as a function of electron momentum, electron scattering angle and four-momentum transfer of the interaction. The total flux-averaged νe charged current cross-section on carbon is measured to be <σ>ϕ = 1.11±0.09(stat) ±0.18(syst)×10-38 cm2/nucleon.
The differential and total cross-section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is 1.23×10-38 cm2/nucleon and the GENIE prediction is 1.08×10-38 cm2/nucleon. The total νe charged current cross-section result is also in agreement with data from the Gargamelle experiment.
Measurement of the neutrino-oxygen neutral-current interaction cross section by observing nuclear deexcitation γ rays
We report the first measurement of the neutrino-oxygen neutral-current quasielastic (NCQE) cross section. It is obtained by observing nuclear deexcitation γ-rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to 3.01 × 1020 protons on target. By selecting only events during the T2K beam window and with well-reconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the 4-30 MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background is primarily nonquasielastic neutral-current interactions and has only 1.2 events from natural radioactivity. The flux-averaged NCQE cross section we measure is 1.55 × 10-38 cm2 with a 68% confidence interval of (1.22, 2.20) × 10-38 cm2 at a median neutrino energy of 630 MeV, compared with the theoretical prediction of 2.01 × 10-38 cm2.