An upgrade of the long baseline neutrino experiment T2K ND280 near detector is under development with the goal to reduce systematic uncertainties in the prediction of number of events at the ...Super-Kamiokande far detector. The upgrade program includes the design and construction of a new neutrino target, a novel highly granular fully active scintillator detector with 3D WLS fiber readout. The ∼2 tonnes 192 × 192 × 56 cm3 detector will be assembled from 2 × 106 plastic scintillator cubes of 1 × 1 × 1 cm3 size. Each cube is read out by three orthogonal Kuraray Y11 WLS fibers threaded through the detector. A detector prototype made of 125 cubes was assembled and tested in a charged particle beam at CERN in October 2017. This paper presents results from studies of light yield, time resolution and optical cross-talk between the cubes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In order to extract neutrino oscillation parameters, long-baseline neutrino oscillation experiments rely on detailed models of neutrino interactions with nuclei. These models constitute an important ...source of systematic uncertainty, partially because detectors to date have been blind to final state neutrons. Three-dimensional projection scintillator trackers comprise components of the near detectors of the next generation long-baseline neutrino experiments. Due to the good timing resolution and fine granularity, this technology is capable of measuring neutron kinetic energy in neutrino interactions on an event-by-event basis and will provide valuable data for refining neutrino interaction models and ways to reconstruct neutrino energy. Two prototypes have been exposed to the neutron beamline at Los Alamos National Laboratory (LANL) in both 2019 and 2020, with neutron energies between 0 and 800 MeV. In order to demonstrate the capability of neutron detection, the total neutron-scintillator cross section as a function of neutron energy is measured and compared to external measurements. The measured total neutron cross section in scintillator between 98 and 688 MeV is 0.36 ± 0.05 barn.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper describes a novel idea of a fine-grained fully-active plastic scintillator detector made of many optically independent 1×1×1cm3 cubes with readout on three orthogonal projections by ...wavelength shifting fibers. The original purpose of this detector is to serve as an active neutrino target for the detection, measurement and identification of the final state particles down to a few tenths MeV kinetic energies. The three readout views as well as the fine granularity ensure powerful localization and measurement of the deposited energy combined with good timing properties and isotropic acceptance. The possible application as a new active target for the T2K near detector, initial simulation studies and R&D test results are reported.
The branching ratio of the structure dependent (SD) radiative K+→e+νeγ decay relative to that of the K+→e+νe(γ) decay including the internal bremsstrahlung (IB) process (Ke2(γ)) has been measured in ...the J-PARC E36 experiment using plastic scintillator/lead sandwich detectors, in contrast to the previous E36 measurement, which used a CsI(Tl) calorimeter. In the analysis, the effect of IB was also taken into account in the SD radiative decay as Ke2γ(γ)SD. By combining the new data with the previous E36 result after revision for the IB correction for Ke2γ(γ)SD, a new value Br(Ke2γ(γ)SD)/Br(Ke2(γ))=1.20±0.07 has been determined. This is consistent with a recent lattice QCD calculation, but larger than the expectation of Chiral Perturbation Theory (ChPT) at order O(p4) and the previous KLOE value. Using the method to relate form factor and branching ratio described in the KLOE paper, the present result is also consistent with the form factor prediction based on a gauged nonlocal chiral quark model, but larger than that from ChPT at order O(p6).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The calorimeter, range detector and active target elements of the T2K near detectors rely on the Hamamatsu Photonics Multi-Pixel Photon Counters (MPPCs) to detect scintillation light produced by ...charged particles. Detailed measurements of the MPPC gain, afterpulsing, crosstalk, dark noise, and photon detection efficiency for low light levels are reported. In order to account for the impact of the MPPC behavior on T2K physics observables, a simulation program has been developed based on these measurements. The simulation is used to predict the energy resolution of the detector.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The structure dependent radiative K+→e+νγ (Ke2γSD+) decay was investigated with stopped positive kaons. The e+ momentum spectra containing 574±30Ke2γSD+ events with a K+→μ+ν (Kμ2) background of 28±19 ...events were measured with and without a photon in coincidence and analyzed with Monte Carlo simulations for acceptance and detector response to extract the ratio of the branching ratio of the Ke2γSD+ decay and the K+→e+ν decay including the internal bremsstrahlung process (Ke2(γ)). A value of Br(Ke2γSD+)/Br(Ke2(γ))=1.12±0.07stat±0.04syst was obtained. This indicates a partial branching ratio, Br(Ke2γSD+,pe>200MeV/c,Eγ>10MeV)/Br(Kμ2)=(1.85±0.11stat±0.07syst)×10−5, which is 25% (∼2.5σ) higher than the previous experimental result.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
SuperFGD, a highly granular scintillator detector, is under construction to reduce systematic uncertainties in the T2K experiment in order to improve the sensitivity to CP-violation in neutrino ...oscillations. SuperFGD will be comprised of about 2×10
6
small (10×10×10 mm
3
) optically isolated polystyrene based plastic scintillator cubes with three orthogonal holes 1.5 mm in diameter. The readout of scintillating light from each cube is provided by three wavelength shifting fibers inserted into the three holes and coupled to MPPC micropixel photosensors. The cubes are covered with a white chemical reflector for optical isolation. The technology of making these cubes, their mechanical properties, their main characteristics obtained during tests with cosmic muons and at the CERN beamline, and the results of the temperature tests are presented in this paper.
Neutrino oscillation experiments require a precise measurement of the neutrino energy. However, the kinematic detection of the final-state neutron in the neutrino interaction is missing in current ...neutrino oscillation experiments. The missing neutron kinematic detection results in a smaller detected neutrino energy than the true neutrino energy. A novel 3D-projection scintillator tracker, which consists of roughly ten million active cubes covered with an optical reflector, is capable of measuring the neutron kinetic energy and direction on an event-by-event basis using the time-of-flight technique thanks to the fast timing, fine granularity, and high light yield. The $\overline{v}$μ interactions tend to produce neutrons in the final state. By measuring the neutron kinetic energy, the $\overline{v}$μ energy can be reconstructed better, allowing a tighter incoming neutrino flux constraint. This article shows the detector's ability to reconstruct neutron kinetic energy and the $\overline{v}$μ flux constraint achieved by selecting the charged-current interactions without mesons or protons in the final state.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Abstract
ND280 is a near detector of the T2K experiment which is
located in the J-PARC accelerator complex in Japan. After a decade
of fruitful data-taking, ND280 is scheduled for upgrade. The
...time-of-flight (ToF) detector, which is described in this article,
is one of three new detectors that will be installed in the basket
of ND280. The ToF detector has a modular structure. Each module
represents an array of 20 plastic scintillator bars which are
stacked in a plane of 2.4 × 2.2 m
2
area. Six modules of
similar construction will be assembled in a cube, thus providing an
almost 4π enclosure for an active neutrino target and two TPCs.
The light emitted by scintillator is absorbed by arrays of
large-area silicon photo-multipliers (SiPMs) which are attached to
both ends of every bar. The readout of SiPMs, shaping and analog
sum of individual SiPM signals within the array are performed by a
discrete circuit amplifier. An average time resolution of about
0.14 ns is achieved for a single bar when measured with cosmic
muons. The detector will be installed in the basket of ND280, where
it will be used to veto particle originating outside the neutrino
target, improve the particle identification and provide a cosmic
trigger for calibration of detectors which are enclosed inside it.
A novel scintillator detector, the SuperFGD, has been selected as the main neutrino target for an upgrade of the T2K experiment ND280 near detector. The detector design will allow nearly 4π coverage ...for neutrino interactions at the near detector and will provide lower energy thresholds, significantly reducing systematic errors for the experiment. The SuperFGD is made of optically-isolated scintillator cubes of size 10×10×10 mm3, providing the required spatial and energy resolution to reduce systematic uncertainties for future T2K runs. The SuperFGD for T2K will have close to two million cubes in a 1920×560×1840 mm3 volume. A prototype made of 24×8×48 cubes was tested at a charged particle beamline at the CERN PS facility. The SuperFGD Prototype was instrumented with readout electronics similar to the future implementation for T2K . Results on electronics and detector response are reported in this paper, along with a discussion of the 3D reconstruction capabilities of this type of detector. Several physics analyses with the prototype data are also discussed, including a study of stopping protons.
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