Detector ND280 Research Articles

New constraint on dark photon at T2K off-axis near detector

The T2K experiment is one of the most powerful long-baseline experiments to investigate neutrino oscillations. The off-axis near detector called ND280 is installed 280 m downstream from the neutrino production target to measure the neutrino energy spectrum. In this paper, we study the capability of the ND280 detector to search for the dark photon produced through the meson rare decay and proton bremsstrahlung processes at the proton beam dump. We find that the ten-year operation of T2K with the ND280 detector excludes the unexplored parameter region for the dark photon mass and kinetic mixing. We also show that a broader parameter region can be searched by the ND280 in the future T2K operation for dark photon as well as U(1)B−L gauge boson.

SuperFGD prototype time resolution studies

The SuperFGD detector will be a novel and important upgrade to the ND280 near detector for both the T2K and Hyper-Kamiokande projects. The main goal of the ND280 upgrade is to reduce systematic uncertainties associated with neutrino flux and cross-section modeling for future studies of neutrino oscillations using the T2K and Hyper-Kamiokande experiments. The upgraded ND280 detector will be able to perform a full exclusive reconstruction of the final state from neutrino-nucleus interactions, including measurements of low momentum protons, pions and for the first time, event-by event measurements of neutron kinematics. Precisely understanding the time resolution is critical for the neutron energy measurements and hence an important factor in reducing the systematic uncertainties. In this paper we present the results of time resolution measurements made with the SuperFGD prototype that consists of 9216 plastic scintillator cubes (cube size is 1 cm3) readout with 1728 wavelength-shifting (WLS) fibers along the three orthogonal directions. We used data from a muon beam exposure at CERN. A time resolution of 0.97 ns was obtained for one readout channel after implementing the time calibration with a correction for time-walk effects. The time resolution improves with increasing energy deposited in a scintillator cube, improving to 0.87 ns for large pulses. Averaging two readout channels for one scintillator cube further improves the time resolution to 0.68 ns implying that signals in different channels are not synchronous. In addition the contribution from the time sampling interval of 2.5 ns is averaged as well. Most importantly, averaging time values from N channels improves the time resolution by ∼ 1/√(N). For example, averaging the time from 2 scintillator cubes with 2 fibers each improves the time resolution to 0.47 ns which is much better than the intrinsic electronics time resolution of 0.72 ns in one channel due to the 2.5 ns sampling window. This indicates that a very good time resolution should be achievable for neutrons since neutron recoils typically interact with several scintillator cubes and in addition produce larger signal amplitudes than muons. Measurements performed with a laser and a wide-bandwidth oscilloscope in which the contribution from the electronics time sampling window was removed demonstrated that the time resolution obtained with the muon beam is not far from the theoretical limit. The intrinsic time resolution of a scintillator cube and one WLS fiber is about 0.67 ns for signals of 56 photo electrons which is typical for minimum ionizing particles.

The Upgrade of the T2K ND280 Detector

The Tokai to Kamiokande (T2K) experiment is a long-baseline neutrino experiment taking data since 2010. The neutrino beam is detected on two sites, the near detector complex close to the neutrino production point, and Super-Kamiokande in a distance of 300 km. The ND280 detector is one of the near detectors and has the purpose to characterize the beam before oscillation as also the measurement of interaction cross sections. Both is crucial to reduce the systematic uncertainties. To improve the latter further, the T2K collaboration decided in 2016 an upgrade of ND280 which includes the installation of a novel scintillator tracker, two time projection chambers and a time of flight system. This upgrade, in combination of an increase of the neutrino beam power from currently 500 kW to 1.3 MW, will roughly increase the statistics by a factor 4 and reduce the systematic uncertainties from 6% to 4%. The new subdetectors are currently being assembled and will be installed in 2022. The upgraded ND280 will also serve as near detector of the next generation long-baseline neutrino oscillation experiment Hyper-Kamiokande.

The SuperFGD prototype PID beam tests results

The near detector ND280 of the T2K experiment will be upgraded in 2022 with the aim of measuring precisely CP violation in neutrinos. The ND280 upgrade consists of the installation of 3 new sub-detector types including SuperFGD, a novel neutrino active target concept. SuperFGD (Super-Fine-Grained-Detector) will have 2 million 1 × 1 × 1cm3 plastic scintillator cubes forming a cube array of 184 × 56 × 192 cm3. Each of the cubes will be intersected by 3 orthogonal WLS fibers with an MPPC on one end. Thanks to its super-fine segmentation, high light yield, and excellent time resolution, great particle identification (PID) capabilities are expected. Since 2018, a set of prototypes have been exposed to particle beams (charged tracks and neutrons) to test this concept. Here the results concerning the particle identification (PID) capabilities using the last prototype are presented.

T2K Experiment: Latest Results and Prospects

The international accelerator neutrino experiment T2K (Tokai-to-Kamioka) began accumulating data in 2010 and has since then accomplished 10 runs in the neutrino and antineutrino modes. The present article reports on the latest results following from the analysis of these data and including the first ever 3 $$\sigma$$ constraints on the CP-violating phase $$\delta_{CP}$$ . Also, the plans for an upgrade of the near detector ND280 are surveyed.

Measurement of the charged-current electron (anti-)neutrino inclusive cross-sections at the T2K off-axis near detector ND280

The electron (anti-)neutrino component of the T2K neutrino beam constitutes the largest background in the measurement of electron (anti-)neutrino appearance at the far detector. The electron neutrino scattering is measured directly with the T2K off-axis near detector, ND280. The selection of the electron (anti-)neutrino events in the plastic scintillator target from both neutrino and anti-neutrino mode beams is discussed in this paper. The flux integrated single differential charged-current inclusive electron (anti-)neutrino cross-sections, dσ/dp and dσ/d cos(θ), and the total cross-sections in a limited phase-space in momentum and scattering angle (p > 300 MeV/c and θ ≤ 45°) are measured using a binned maximum likelihood fit and compared to the neutrino Monte Carlo generator predictions, resulting in good agreement.

Development of resistive micromegas TPCS for the T2K experiment

The long baseline neutrino experiment T2K has launched the upgrade project of its near detector ND280, crucial to reduce the systematic uncertainty to less than 4%. An essential component of this upgrade consists of two new High-Angle TPCs (HA-TPCs), for 3D track reconstruction, momentum measurement and particle identification. These TPCs will be equipped with 32 resistive bulk-micromegas modules. The field cage will be realized with laminated composite panels covered with a kapton foil with copper strips for electric field shaping. The 34x42 cm2 micromegas will use a ∼0.5 MΩ/square Diamond-Like Carbon (DLC) foil to spread the charge over the pad plane, each pad being ∼1 cm2. In summer 2018, we have tested a resistive bulk-micromegas prototype on the Harp TPC cage with the CERN/PS beam with excellent results both for the space point resolution and for dE/dx resolution. We report on the design of the HA-TPCs and the preliminary results of the prototype performances with 0.8 GeV/c particles.

Search for heavy neutrinos with the T2K near detector ND280

This paper reports on the search for heavy neutrinos with masses in the range $140 < M_N < 493$ MeV/c$^2$ using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are $N \to \ell^{\pm}_{\alpha} \pi^{\mp}$ and $N \to \ell^+_{\alpha} \ell^-_{\beta} \nu (\bar\nu)$ ($\alpha,\beta=e,\mu$). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavoured currents ($U_e^2$, $U_{\mu}^2$, $U_{\tau}^2$) as a function of the heavy neutrino mass, e.g. $U_e^2 < 10^{-9}$ at $90\%$ C.L. for a mass of $390$ MeV/c$^2$. These constraints are competitive with previous experiments.

Development of a 3D highly granular scintillator neutrino detector for the T2K experiment

The long baseline neutrino experiment T2K has launched the upgrade project of its near detector ND280, crucial to reduce the systematic uncertainties in the prediction of number of events at the far detector to less than 4%. An essential component of this upgrade is a highly segmented scintillator detector, acting as a fully active target for neutrino interactions, called SuperFGD, with dimensions of 192×192×56 cm3 a total mass of about 2 tonnes. Prototypes of this detector have been tested in a beam of charged particles at CERN in 2017 and 2018. The detector response, including the light yield and the time resolution are presented. The installation of new components for the upgrade of ND280 is planned in 2021.

Parameters of a fine-grained scintillator detector prototype with 3D WLS fiber readout for a T2K ND280 neutrino active target

Abstract An upgrade of the long baseline neutrino experiment T2K near detector ND280 is currently being designed. The upgrade program includes the development a new highly granular fully active scintillator neutrino detector as a neutrino target. The baseline concept of the detector represents an array of about 2 × 1 0 6 small scintillator cubes each of 1 cm 3 . The 3D signal readout from each cube is provided by three orthogonal 1.0 mm Kuraray Y11 multiclad WLS fibers read out by SiPMs. A small prototype of the detector assembled of 125 cubes was tested in a beam of charged particles as well as with cosmic muons. Obtained parameters of the prototype are reported in this paper.

Selection of electron (anti-)neutrinos at the T2K near detector ND280

The intrinsic electron neutrino contamination of the T2K neutrino beam provides the single largest background in the measurement of electron neutrino appearance in T2K. These electron neutrinos can be measured directly in the T2K near detector ND280. Measurements of the intrinsic electron (anti-)neutrino backgrounds from the anti-neutrino running are shown, including details on the event selections and rejection of the large background of muons, photons, protons and pions. The νe and beam compositions are then extracted and the rescaling parameters of the expected rate of νe and events are f(νe) = 1.250 ± 0.135(stats.) ± 0.122(syst.) and respectively.

Muon neutrino and anti-neutrino selection in the tracker of the T2K off-axis near detector

T2K (Tokai to Kamioka) is a long-baseline neutrino oscillation experiment located in Japan. Since its discovery of electron neutrino appearance in 2013 excluding θ13 = 0 with a significance of 7.3σ, T2K has switched its beam magnet polarities to run in anti-neutrino beam mode in order to enhance its sensitivity to measure anti-electron neutrino appearence. The beam is dominated by muon antineutrinos; however it also contains a sizable contamination from muon neutrinos. The analysis of both νµ and interactions in the off-axis near detector ND280, provides a significant reduction of the flux prediction and cross-section modelling systematic uncertainties in the oscillation analysis. ND280 data also gives us the opportunity to measure cross-sections for processes that have not yet been thoroughly studied for antineutrinos at the energy range of ∼1 GeV. The second largest reaction type at this energy range after the charged-current (CC) quasi-elastic reaction are processes involving pion production. The poster will present the selections of CC interactions of both antineutrinos and neutrinos in the ND280 tracker. It will also cover the separation into three sub-samples of the CC sample based on the pion content in each event.

The WAGASCI detector as an off-axis near detector of the T2K and Hyper-Kamiokande experiments

In the search for CP violation at the T2K and future Hyper-Kamiokande experiments, it is crucial to reduce the present systematic uncertainties. The current T2K near detector, ND280, reduces the uncertainties coming from the neutrino beam and cross-section models from 11.9% to 5.4% in the νe appearance channel. These residual uncertainties mostly come from intrinsic limitations of ND280 due to its difference in target material and angular acceptance with the far detector.In order to show evidence (subsequently observation) of the CP violation in the T2K phase-II and Hyper-Kamiokande experiments, this paper proposes an upgrade of the ND280 detector. It uses a 3D grid scintillator structure surrounded by Time Projecting Chambers in order to reconstruct particles with ∼ 4π acceptance.

Towards a νμ Charged-Current Cross Section on Water using the T2K Near Detector

The T2K collaboration presents studies of muon neutrino event distributions on water, at neutrino energies of the order of 1 GeV, using a vertex algorithm at the near detector ND280. This sample can be used to measure neutrino interactions on water and to constrain the expected neutrino energy spectrum at Super-Kamiokande. This sample requires vertices in the FGD2, a detector composed of interleaved water and scintillator bars. Water interactions are selected by using a Kalman Filter to reconstruct the vertices of multiple-track events. Few measurements of the water cross section have been made, and such measurements have the potential to reduce interaction model systematics in neutrino oscillation analyses.

Measurement of $$\bar \nu _\mu$$ CC interactions with the ND280 detector of the T2K experiment

This paper presents a measurement of the \(\bar \nu _\mu\) CC interactions both in neutrino and anti-neutrino data taking modes, using the near detector (ND280) of the T2K experiment. In neutrino beam mode a ∼ 4% intrinsic \(\bar \nu _\mu\) component in the total neutrino flux is expected. The charged current interactions of \(\bar \nu _\mu\) are selected combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeter of ND280. The measured ratio between the observed \(\bar \nu _\mu\) beam component and the prediction is 1.01 ± 0.13, providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. This measure helps in the reduction of the large systematic uncertainty on the ratio \(\sigma _{\bar \nu } /\sigma _\nu\) which affects the ν μ disappearance analysis. A precise measurement of \(\bar \nu _\mu\) in anti-neutrino beam mode is also presented. This measurement is particularly of interest for the anti-neutrino data taking, since it is used to provide the ND280 constraint on flux and cross section parameters to the oscillation analyses.

Publisher’s Note: Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector [Phys. Rev. D 89, 092003 (2014)

Publisher’s Note: Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector [Phys. Rev. D 89, 092003 (2014)

Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector

The T2K experiment has reported the first observation of the appearance of electron neutrinos in a muon neutrino beam. The main and irreducible background to the appearance signal comes from the presence in the neutrino beam of a small intrinsic component of electron neutrinos originating from muon and kaon decays. In T2K, this component is expected to represent 1.2% of the total neutrino flux. A measurement of this component using the near detector (ND280), located 280 m from the target, is presented. The charged current interactions of electron neutrinos are selected by combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeters of ND280. The measured ratio between the observed electron neutrino beam component and the prediction is 1.01+-0.10 providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. Electron neutrinos coming from muons and kaons decay are also separately measured, resulting in a ratio with respect to the prediction of 0.68+-0.30 and 1.10+-0.14, respectively.

Improved measurement of $\nu_{\mu}$-induced charged-current single $\pi^{+}$ production flux-averaged absolute cross-section on water using the P0D detector of the ND280 detector complex in the T2K experiment

Improved measurement of $\nu_{\mu}$-induced charged-current single $\pi^{+}$ production flux-averaged absolute cross-section on water using the P0D detector of the ND280 detector complex in the T2K experiment

The electromagnetic calorimeter for the T2K near detector ND280

The T2K experiment studies oscillations of an off-axis muon neutrinobeam between the J-PARC accelerator complex and the Super-Kamiokandedetector. Special emphasis is placed on measuring the mixing angleθ13 by observing νe appearance via the sub-dominant νμ → νeoscillation and searching for CP violationin the lepton sector.The experiment includes a sophisticated, off-axis, near detector, theND280, situated280 m downstream of the neutrino production target in order to measurethe properties of the neutrino beam and to understand better neutrinointeractions at the energy scale below a few GeV. The data collectedwith the ND280 are used to study charged-and neutral-current neutrino interaction rates and kinematics prior tooscillation,in order to reduce uncertainties in the oscillation measurementsby the far detector.A key element of the near detector is the ND280 electromagneticcalorimeter (ECal), consisting ofactive scintillator bars sandwiched between lead sheets and read outwith multi-pixel photon counters (MPPCs). The ECal is vital to thereconstruction of neutral particles, and the identification of chargedparticle species.The ECal surrounds the Pi-0 detector (PØD) and the tracking regionof the ND280, and is enclosed in the former UA1/NOMAD dipole magnet. This paper describes the design, construction and assembly of the ECal, as well as the materials from which it is composed. The electronic and data acquisition (DAQ) systems are discussed, andperformance of the ECal modules, as deduced from measurementswith particle beams, cosmic rays, the calibration system, and T2K data, is described.

Pion production in the T2K experiment

Background: Pion production gives information on the axial form factors of nucleon resonances. It also introduces a noticeable background to quasi-elastic measurements on nuclear targets and thus has a significant impact on precision studies of neutrino oscillation parameters. Purpose: To clarify neutrino-induced pion production on nucleons and nuclei. Method: The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used for the description of neutrino-nucleus reactions. Results: Theoretical results for differential cross sections for the T2K neutrino flux at the ND280 detector and integrated cross sections as a function of neutrino energy are given. Two sets of pion production data on elementary targets are used as inputs to obtain limits for pion production in neutrino-nucleus reactions. Conclusions: Pion production in the T2K ND280 detector can help to narrow down the uncertainties in the elementary pion production cross sections. It can also give valuable information on the nucleon-Delta axial form factor.