Physics potential of a long-baseline neutrino oscillation experiment using a J-PARC neutrino beam and Hyper-Kamiokande

Hyper-Kamiokande will be a next-generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of CP asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this paper, the physics potential of a long-baseline neutrino experiment using the Hyper- Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5MW ×107s integrated proton beam power (corresponding to 1.56 × 1022protons on target with a 30 GeV proton beam) to a 2.5° off-axis neutrino beam, it is expected that the leptonic CP phase δCPcan be determined to better than 19 degrees for all possible values of δCP, and CP violation can be established with a statistical significance of more than 3 σ (5 σ) for 76% (58%) of the δCPparameter space. Using both νeappearance and νμ disappearance data, the expected 1 σ uncertainty of sin2Θ23is 0.015(0.006) for sin2Θ23= 0.5(0.45)

Neutrino oscillation physics potential of the T2K experiment

The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle Θ13 have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal sin2 2Θ23, the octant of Θ23, and the mass hierarchy, in addition to the measurements of δCP, sin2 Θ23, and Δm232, for various combinations of ν-mode and ν-mode data-taking. With an exposure of 7.8 × 1021 protons-on-target, T2K can achieve 1 σ resolution of 0.050 (0.054) on sin2 Θ23 and 0.040 (0.045) × 10-3 eV2 on Δm232 for 100% (50%) neutrino beam mode running assuming sin2 Θ23 = 0.5 and Δm232 = 2.4 × 10-3 eV2. T2K will have sensitivity to the CP-violating phase δCP at 90% C.L. or better over a significant range. For example, if sin2 2Θ23 is maximal (i.e. Θ23 = 45°) the range is -115° \u3c δCP \u3c -60° for normal hierarchy and +50° \u3c δCP \u3c +130° for inverted hierarchy. When T2K data is combined with data from the NOνA experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero δCP is substantially increased compared to if each experiment is analyzed alone

Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6 × 10\u3csup\u3e20\u3c/sup\u3eprotons on target

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: normal hierarchy: sin2θ23= 0.514-0.056+0.055and Δm322= (2.51 ± 0.10) × 10-3eV2/c4and inverted hierarchy: sin2θ23= 0.511 ± 0.055 and Δm132= (2.48 ± 0.10) × 10-3eV2/c4. The analysis accounts for multinucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters, |Δm2|, sin2θ23, sin2θ13, δCP, and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region δCP= [0.15; 0.83]π for normal hierarchy and δCP= [-0.08; 1.09]π for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes factor of 2.2. The most probable values and 68% one-dimensional credible intervals for the other oscillation parameters, when reactor data are included, are sin2θ23= 0.528-0.038+0.055and |Δm322| = (2.51 ± 0.11) × 10-3eV2/c4

Measurement of the νμcharged current quasielastic cross section on carbon with the T2K on-axis neutrino beam

We report a measurement of the νμcharged current quasielastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasielastic cross-sections on carbon at mean neutrino energies of 1.94 GeVand 0.93 GeVare (11.95 ± 0.19(stat)-1.47+1.82(syst)) × 10-39cm2/neutron, and (10.64 ± 0.37(stat)-1.65+2.03(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

Measurement of the electron neutrino charged-current interaction rate on water with the T2K ND280 π0 detector

This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above 1.5 GeV using the large fiducial mass of the T2K π0 detector. The predominant portion of the νe flux (∼85%) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is 0.89±0.08(stat)±0.11(sys), and with the water targets emptied is 0.90±0.09(stat)±0.13(sys). The ratio obtained for the interactions on water only from an event subtraction method is 0.87±0.33(stat)±0.21(sys). This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors

Search for short baseline νe disappearance with the T2K near detector

The T2K experiment has performed a search for νe disappearance due to sterile neutrinos using 5.9×1020 protons on target for a baseline of 280 m in a neutrino beam peaked at about 500 MeV. A sample of νe CC interactions in the off-axis near detector has been selected with a purity of 63% and an efficiency of 26%. The p-value for the null hypothesis is 0.085 and the excluded region at 95% C.L. is approximately sin22θee\u3e0.3 for Δmeff2\u3e7eV2/c4

Measurement of the νμ charged-current quasielastic cross section on carbon with the ND280 detector at T2K

This paper reports a measurement by the T2K experiment of the νμ charged current quasielastic (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 «