Auswahl der wissenschaftlichen Literatur zum Thema „ND280 upgrade“

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.

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 m2 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.

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 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.

Hyper-Kamiokande, the next-generation neutrino observatory in Japan, evolves from its predecessors, Kamiokande, Super-Kamiokande and T2K, with a significant upgrade to a 258-kton water Cherenkov detector equipped with 20,000 PMTs. Hyper-Kamiokande will host an extremely rich and broad physics program, covering areas from neutrino astrophysics to nucleon decay searches and precision neutrino oscillation measurements. Positioned as the far detector for the JPARC neutrino beam, with a baseline of 295 km, and utilizing near detectors such as the upgraded ND280 detector and INGRID currently used by the T2K experiment, Hyper-Kamiokande will have excellent sensitivity to CP violation signatures in neutrino oscillations. Set to be completed in 2027, we summarize Hyper-Kamiokande’s status and physics program, with an emphasis on its CP violation searches.

Abstract 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.

T2K is an accelerator-based neutrino experiment providing world-leading measurements of the parameters governing neutrino oscillations. T2K data enabled the first 3 [Formula: see text] exclusion for some intervals of the CP-violating phase [Formula: see text] and precision measurements of the atmospheric parameters [Formula: see text], [Formula: see text]. T2K uses a beam of muon neutrinos and antineutrinos produced at the Japan Proton Accelerator Research Centre (J-PARC) and a series of detectors located at J-PARC and in Kamioka, 295km away, to measure oscillations from neutrino event rates and spectra. The T2K beam will be upgraded with increased power in 2022 and, combined with an upgrade of the ND280 near detector, will usher in a new important physics period for T2K. In preparation for the new physics run, the T2K collaboration is working on an updated oscillation analysis to improve the control of systematic uncertainties. The status of the new analysis developments and the plan to deploy the beam and ND280 upgrade are reviewed.

Le travail de thèse se situe dans le domaine de la physique des neutrinos dans le cadre de l'expérience T2K. La thèse est divisée en deux sujets : la caractérisation des détecteurs et la préparation de l'analyse physique. Dans le contexte de la mise à niveau du détecteur proche de T2K - ND280, un modèle a été développé et utilisé pour caractériser la dispersion de charge dans le détecteur Micromegas résistif novateur (ERAM). De plus, le gain et la résolution énergétique de chaque ERAM ont été obtenus, pad par pad, pour une caractérisation complète. Les résultats ont directement conduit à la sélection d'ERAM spécifiques pour une installation à des positions spécifiques sur les plans d'anode des chambres à projection temporelle à grand angle. Au total, 37 ERAM ont été caractérisés avec succès en utilisant des données aux rayons X provenant d'un banc d'essai au CERN. Ces informations ont également été utilisées pour la reconstruction. L'amélioration des statistiques et de l'efficacité de détection des événements quasi-élastiques en courant chargé dans la région de haut Q² (transfert de moment à quatre dimensions) après la mise à niveau du ND280 a été étudiée. La question de savoir dans quelle mesure les incertitudes de haut Q² seront effectivement contraintes après la mise à niveau du ND280 par les 4 paramètres de haut Q² dans le modèle de section efficace neutrino-noyau a été abordée en utilisant les outils de re-pondération de T2K et le programme d'ajustement - GUNDAM. Une source importante des incertitudes de haut Q² est le modèle de facteur de forme axial-vecteur (dipolaire) actuellement utilisé dans le modèle de section efficace. Certains modèles alternatifs de facteur de forme qui peuvent mieux contraindre ces incertitudes ont également été étudiés. L'effet des incertitudes dans l'estimation de l'énergie de liaison des nucléons sur différentes variables (cinématique des muons, énergie des neutrinos, etc.) a été étudié. Des splines par bins ont été produites pour les 4 paramètres de l'énergie de liaison dans le modèle de section efficace dans le contexte de l'analyse des oscillations utilisant les données collectées en 2024
The PhD work is in the field of Neutrino Physics as a part of the T2K experiment. The thesis is divided into two subjects- detector characterization and preparation of physics analysis. In the context of the upgrade of T2K near detector- ND280, a model was developed and utilized to characterize the charge spreading in novel resistive Micromegas (ERAM) detector. In addition, pad-by-pad gain and energy resolution was obtained for each ERAM for a complete characterization. The results directly led to the selection of specific ERAMs for installation at specific positions in the High Angle-Time Projection Chamber anode planes for charge readout. In total, 37 ERAMs were successfully characterized using X-ray data from a test bench at CERN. This information was also used as inputs for reconstruction. Improvement in statistics and detection efficiency of charged-current quasi-elastic events in high Q² (4-momentum transfer) region after the ND280 upgrade was studied. The question of- how effectively the high Q² uncertainties will be constrained after the ND280 upgrade by the 4 high Q² parameters in the neutrino-nucleus cross-section model was addressed using T2K re-weighting tools and the ND280 fitter- GUNDAM. An important source of the high Q² uncertainties is the axial-vector form factor model (dipole) used currently in the cross-section model. Some alternative form factor models that can better constrain these uncertainties were also studied. The effect of uncertainties in nucleon removal energy estimation on different variables (muon kinematics, neutrino energy, etc.) was studied. Binned splines were produced for the 4 removal energy parameters in the cross-section model in the context of Oscillation Analysis using data collected in 2024