Generation Underground Water Cherenkov Detector Research Articles

Large area photo-detection system using 3” PMTs for the Hyper-Kamiokande Outer-Detector

Hyper-Kamiokande, scheduled to begin construction as soon as 2020, is a next generation underground water Cherenkov detector, based on the highly successful Super- Kamiokande experiment. It will serve as a far detector, 295 km away, of a long baseline neutrino experiment for the upgraded J-PARC beam in Japan. It will also be a detector capable of observing — far beyond the sensitivity of the Super-Kamiokande detector — proton decay, atmospheric neutrinos, and neutrinos from astronomical sources.An Outer Detector (OD) consisting of PMTs mounted behind the inner detector PMTs and facing outwards to view the outer shell of the cylindrical tank, would provide topological information to identify interactions originating from particles outside the inner detector. Any optimization would lead to a significant improvement for the physics goals of the experiment, which are the measurement of the CP leptonic phase and the determination of the neutrino mass hierarchy.An original setup using small 3” PMTs is being designed for the Hyper-Kamiokande OD. They would give better redundancy, spatial, and angular resolution, as they would be twice or three times more photosensors that the original 8” design proposal of the experiment, and for a reduce cost. Several 3” PMTs candidates considered for the Hyper-Kamiokande OD have been characterized at Queen Mary University London. They all show a very low dark counts and good collection efficiency, which makes them excellent choice to be used in the experiment.

Evaluation of position dependent performance of 3-inch PMTs for Multi-PMT development

Hyper-Kamiokande detector is proposed as a next generation underground water Cherenkov detector in Japan, and is planned to be an order of magnitude bigger than its predecessor, Super-Kamiokande. In order to further improve the detector capabilities in both low and high energy sectors, the multi-PMT modules instrumented with multiple 3-inch PMTs are being developed, in addition to the improved high quantum efficiency 20-inch PMTs. We developed a moveable laser system that can illuminate different positions on the photocathode to measure the characterization of the 3-inch PMTs as a function of the position on the photocathode.

Sensitivity of new physics by joint analysis of neutrino oscillation on Hyper-Kamiokande

Hyper-Kamiokande (Hyper-K) is a proposed next generation underground water Cherenkov detector with a total (fiducial) mass of 516 (374) kilotons, approximately 10 (17) times as large as that of Super-Kamiokande. It will serve as a far detector of a long baseline neutrino oscillation experiment envisioned for the upgraded J-PARC and will also observe atmospheric neutrinos. The design of Hyper-K is based on the highly successful Super-Kamiokande (Super-K), making full use of a well-proven technology. In this work, we will discuss Hyper-K’s sensitivity to the leptonic CP violation and the neutrino mass hierarchy by studying the oscillations of both beam and atmospheric neutrinos. The combined analysis can increase both the sensitivity of mass hierarchy and CP violation. The sensitivity of mass hierarchy can reach 5σ and the fraction of 3σ to observe leptonic CP violation can reach 90%, with sin2θ23 = 0.5 after 10 years running (a. 2.6 Mton·year exposure).

The Hyper-Kamiokande Experiment

The Hyper-Kamiokande experiment is a next generation underground water Cherenkov detector, based on the highly successful Super-Kamiokande experiment. It will serve as a far detector of a long baseline neutrino experiment for the J-PARC neutrino beam, with the main focus the determination of CP violation, and will also be a detector capable of observing - far beyond the sensitivity of the Super-Kamiokande detector - proton decay, atmospheric neutrinos, and neutrinos from astronomical sources.

Neutrino physics perspectives with Hyper-Kamiokande

The Hyper-Kamiokande experiment is a proposed next generation underground water Cherenkov detector. It will serve as a far detector of a long baseline neutrino oscillation experiment envisioned for the upgraded J-PARC beam, and is capable of observing – far beyond the sensitivity of the Super-Kamiokande detector – proton decays, atmospheric neutrinos, and neutrinos from astronomical origins. The baseline design of Hyper-Kamiokande is based on the highly successful Super-Kamiokande, but with a 20 times larger detector and higher beam power.

Sensitivity to the neutrino oscillation parameters in the Hyper-Kamiokande experiment

The Hyper-Kamiokande (Hyper-K) [1, 2] detector is a next generation underground water Cherenkov detector that will serve as the far detector of a long-baseline neutrino experiment (T2HK) located in Japan. T2HK is a natural extension of the very successful T2K experiment.The upgraded facilities at J-PARC will deliver an off-axis narrow band (≈0.6GeV) (anti)neutrino beam (750kW-1MW) directed to Hyper-K that will be used to measure the appearance and disappearance parameters with unprecedented precision as well as potentially discover CP violation in the lepton sector.If the mass hierarchy is known, Hyper-K is expected to determine the CP phase to better than 19 degrees for all possible values of δCP and CP violation can be determined at 3σ for 76% of the delta parameter space (considering 5 years exposure to neutrino beam produced by the 1.66 MW J-PARC proton synchrotron) [2].

The development of a hybrid photo-detector (HPD) for the Hyper-Kamiokande project

We are developing hybrid photo-detectors (HPDs) for Hyper-Kamiokande, which is a next generation underground water Cherenkov detector designed to search for proton decay and study many topics related to neutrino physics and astrophysics. A verification study of the suitability of HPDs for a water Cherenkov detector in a 200-ton tank is planned. In advance, we evaluated the performances of an 8-in. prototype HPD and tested them in water to confirm their safe operation. The prototype shows better single photon sensitivity and timing resolution than the conventional PMTs used in Super-Kamiokande.

The Hyper-Kamiokande project

The Hyper-Kamiokande, which we are currently developing, is designed to be the next decadeʼs flagship experiment for the study of neutrino oscillations, nucleon decays, and astrophysical neutrinos. The detector is the third generation underground water Cherenkov detector at Kamioka. Holding 1 million ton water target being about 20 times larger than the Super-Kamiokande, the detector will extend the sensitivity to search for baryon-number-violated proton (and bound neutron) decays by one order of magnitude or more to test various grand unified theories. It also aims to explore the full picture of neutrino masses and mixings by using intense accelerator and atmospheric neutrinos. These experimental studies would become windows to see physics at the grand unification scale of ∼1016GeV which is far beyond the energy scale of accelerator based particle physics. The detector also serves as an astrophysical neutrino observatory aiming to study the explosion mechanism of core-collapse supernova, the history of star formation and heavy element synthesis in the universe, WIMP dark matters trapped in the Sun, Earth, and Galaxy, and other astrophysical neutrino sources.Physics potential of the Hyper-Kamiokande is estimated based on the well proven water Cherenkov technology and its detector performance. Feasibility of the one megaton size detector has been shown by its baseline design, and the detector design is being optimized at present. By taking into account the production rate of photo-sensors and estimated construction period, the Hyper-Kamiokande is expected to start its operation in 2023.