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T2K is a long-baseline neutrino experiment that aims to investigate the CP violation in the neutrino sector. An upgrade of the ND280, which is one of the T2K near detectors, is in progress. The active target detector of the upgraded ND280 is a segmented highly granular plastic scintillation detector (SuperFGD) consisting of about two million scintillator cubes. About sixty thousand silicon photo-multipliers (SiPMs) coupled with wavelength shifting fibers are used for light readout. The fibers go through the scintillator cubes along the orthogonal three directions. We developed a novel system based on LEDs and notched light guide plates for in-situ calibration of the SuperFGD. The developed system can distribute LED light to SiPMs simultaneously with high uniformity and can be used for gain calibration and stability monitor of the signal readout. In addition, it can fit in the confined space of the SuperFGD due to its thin structure. In this paper, we report the design and the performance of the calibration system.

The T2K (Tokai-to-Kamioka) is a long baseline neutrino experiment designed to study various parameters that rule neutrino oscillations, with an intense beam of muon neutrinos. A near detector complex (ND280) is used to constrain non-oscillated flux and hence to predict the expected number of events in the far detector (Super-Kamiokande). The difference in the target material between the far (water) and near (scintillator, hydrocarbon) detectors leads to the main non-canceling systematic uncertainty for the oscillation analysis. In order to reduce this uncertainty a new water grid and scintillator detector, WAGASCI, has been proposed. The detector will be operated at the J-PARC neutrino beam line with the main physics goal to measure the charged current neutrino cross section ratio between water and hydrocarbon with a few percent accuracy. Further physics program may include high-precision measurements of different charged current neutrino interaction channels. The concept of the new detector will be covered together with the actual construction plan.

Abstract A new event reconstruction algorithm based on a maximum likelihood method has been developed for Super-Kamiokande. Its improved kinematic and particle identification capabilities enable the analysis of atmospheric neutrino data in a detector volume 32% larger than previous analyses and increase the sensitivity to the neutrino mass hierarchy. Analysis of a 253.9 kton$\\cdot$year exposure of the Super-Kamiokande IV atmospheric neutrino data has yielded a weak preference for the normal hierarchy, disfavoring the inverted hierarchy at 74% assuming oscillations at the best fit of the analysis.

The T2K experiment presents new measurements of neutrino oscillation parameters using protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on and the impact of priors on the measurement. Both analyses prefer the normal mass ordering and upper octant of with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on from reactors, using Feldman-Cousins corrected intervals, and using constant intervals. The CP-violating phase is constrained to using Feldman-Cousins corrected intervals, and is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than credible level using a flat prior in and just below using a flat prior in When the external constraint on is removed, in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.

The T2K experiment presents new measurements of neutrino oscillation parameters using $$19.7(16.3)\\times 10^{20}$$ 19.7(16.3)×1020 protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional $$4.7\\times 10^{20}$$ 4.7×1020 POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on $$\\sin ^2\\theta _{13}$$ sin2θ13 and the impact of priors on the $$\\delta _{\\textrm{CP}}$$ δCP measurement. Both analyses prefer the normal mass ordering and upper octant of $$\\sin ^2\\theta _{23}$$ sin2θ23 with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on $$\\sin ^2\\theta _{13}$$ sin2θ13 from reactors, $$\\sin ^2\\theta _{23}=0.561^{+0.021}_{-0.032}$$ sin2θ23=0.561-0.032+0.021 using Feldman–Cousins corrected intervals, and $$\\varDelta {}m^2_{32}=2.494_{-0.058}^{+0.041}\\times 10^{-3}~\\text {eV}^2$$ Δm322=2.494-0.058+0.041×10-3eV2 using constant $$\\varDelta \\chi ^{2}$$ Δχ2 intervals. The CP-violating phase is constrained to $$\\delta _{\\textrm{CP}}=-1.97_{-0.70}^{+0.97}$$ δCP=-1.97-0.70+0.97 using Feldman–Cousins corrected intervals, and $$\\delta _{\\textrm{CP}}=0,\\pi $$ δCP=0,π is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than $$2\\sigma $$ 2σ credible level using a flat prior in $$\\delta _{\\textrm{CP}},$$ δCP, and just below $$2\\sigma $$ 2σ using a flat prior in $$\\sin \\delta _{\\textrm{CP}}.$$ sinδCP. When the external constraint on $$\\sin ^2\\theta _{13}$$ sin2θ13 is removed, $$\\sin ^2\\theta _{13}=28.0^{+2.8}_{-6.5}\\times 10^{-3},$$ sin2θ13=28.0-6.5+2.8×10-3, in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.

We present a new measurement of $J/\\psi$ production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the ($J/\\psi$)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the ($J/\\psi$)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.

The production of $\\rho$ , $\\omega$ and $\\phi$ vector-mesons, detected through their $\\mu\\mu$ decay channel, is studied in p-W, S-S, S-Cu and S-U reactions at 200 GeV/c per nucleon incident momentum. Their inclusive cross-sections are determined in various transverse momentum intervals and their dependence on the projectile and target mass numbers is investigated. The relative yield $B_{\\mu\\mu}\\sigma_{\\phi}/(B_{\\mu\\mu}\\sigma_{\\rho} + B_{\\mu\\mu}\\sigma_{\\omega})$ is measured, both as a function of the transverse momentum, pT, and of the collision centrality. While this ratio exhibits no significant dependence with pT, it clearly increases with the centrality of the collision. Effective temperatures deduced from the transverse mass spectra, $d\\sigma/dM_T$ , lead to values of $T_{\\rho + \\omega}$ equal or slightly higher than $T_{\\phi}$ . Both these effective temperatures smoothly increase from p-W to S-U reactions.

The PHENIX experiment at RHIC measured single electron spectra in p + p, d + Au and Au + Au collisions at \\(\\sqrt{s_{NN}} = 200\\) GeV, and in Au + Au collisions at \\(\\sqrt{s_{NN}} = 62.4\\) GeV. In these spectra, electrons from semi-leptonic decays of charmed particles are the dominant contribution after subtraction of all 'photonic' sources (photon conversions, Dalitz decays, decays of light vector mesons). The p + p open charm production cross-section is found to be in good agreement with pQCD NLO calculations. The shape of the distributions obtained for p + p interactions is compared with those observed for nucleus-nucleus collisions. From p + p to d + Au and Au + Au interactions, open charm production is found to scale with the number of binary collisions \\(N_{\\rm coll}\\). Au + Au data at \\(\\sqrt{s_{NN}} = 62.4\\) GeV is compatible with the ISR p + p results scaled by \\(N_{\\rm coll}\\). The elliptic flow parameter v2 of heavy flavor electrons has also been measured, and is found to be non-zero in the intermediate pT range.

Abstract The T2K experiment presents new measurements of neutrino oscillation parameters using $$19.7(16.3)\\times 10^{20}$$ 19.7 ( 16.3 ) × 10 20 protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional $$4.7\\times 10^{20}$$ 4.7 × 10 20 POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on $$\\sin ^2\\theta _{13}$$ sin 2 θ 13 and the impact of priors on the $$\\delta _{\\textrm{CP}}$$ δ CP measurement. Both analyses prefer the normal mass ordering and upper octant of $$\\sin ^2\\theta _{23}$$ sin 2 θ 23 with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on $$\\sin ^2\\theta _{13}$$ sin 2 θ 13 from reactors, $$\\sin ^2\\theta _{23}=0.561^{+0.021}_{-0.032}$$ sin 2 θ 23 = 0 . 561 - 0.032 + 0.021 using Feldman–Cousins corrected intervals, and $$\\varDelta {}m^2_{32}=2.494_{-0.058}^{+0.041}\\times 10^{-3}~\\text {eV}^2$$ Δ m 32 2 = 2 . 494 - 0.058 + 0.041 × 10 - 3 eV 2 using constant $$\\varDelta \\chi ^{2}$$ Δ χ 2 intervals. The CP-violating phase is constrained to $$\\delta _{\\textrm{CP}}=-1.97_{-0.70}^{+0.97}$$ δ CP = - 1 . 97 - 0.70 + 0.97 using Feldman–Cousins corrected intervals, and $$\\delta _{\\textrm{CP}}=0,\\pi $$ δ CP = 0 , π is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than $$2\\sigma $$ 2 σ credible level using a flat prior in $$\\delta _{\\textrm{CP}},$$ δ CP , and just below $$2\\sigma $$ 2 σ using a flat prior in $$\\sin \\delta _{\\textrm{CP}}.$$ sin δ CP . When the external constraint on $$\\sin ^2\\theta _{13}$$ sin 2 θ 13 is removed, $$\\sin ^2\\theta _{13}=28.0^{+2.8}_{-6.5}\\times 10^{-3},$$ sin 2 θ 13 = 28 . 0 - 6.5 + 2.8 × 10 - 3 , in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.