Proper-time Resolution Function for Measurement of Time Evolution of B Mesons at the KEK B-Factory

The proper-time resolution function for the measurement of the time evolution of B mesons with the Belle detector at KEKB is studied in detail. The obtained resolution function is applied to the measurement of B meson lifetimes, the B0-B0bar oscillation frequency and time-dependent CP asymmetries.Comment: 25 pages, 18 figures, to be published in NIM A, replaced with revised versio

Application of Hamamatsu MPPC to T2K Neutrino Detectors

A special type of Hamamatsu MPPC, with a sensitive area of 1.3x1.3mm^2 containing 667 pixels with 50x50um^2 each, has been developed for the near neutrino detector in the T2K long baseline neutrino experiment. About 60 000 MPPCs will be used in total to read out the plastic scintillator detectors with wavelength shifting fibers. We report on the basic performance of MPPCs produced for T2K.Comment: Contribution to the proceedings of NDIP 2008, Aix-les-Bains, France, June 15-20, 200

Performance of Multi-Pixel Photon Counters for the T2K near detectors

We have developed a Multi-Pixel Photon Counter (MPPC) for the neutrino detectors of T2K experiment. About 64,000 MPPCs have been produced and tested in about a year. In order to characterize a large number of MPPCs, we have developed a system that simultaneously measures 64 MPPCs with various bias voltage and temperature. The performance of MPPCs are found to satisfy the requirement of T2K experiment. In this paper, we present the performance of 17,686 MPPCs measured at Kyoto University.Comment: 15 pages, 14 figure

Status of Neutrino Masses and Mixing and Future Perspectives

Status of the problem of neutrino masses, mixing and oscillations is discussed. Future perspectives are briefly considered.Comment: Report at the conference IRGAC 2006, Barcelona July 11-15 200

A new design for the CERN-Fr\'ejus neutrino Super Beam

We present an optimization of the hadron focusing system for a low-energy high-intensity conventional neutrino beam (Super-Beam) proposed on the basis of the HP-SPL at CERN with a beam power of 4 MW and an energy of 4.5 GeV. The far detector would be a 440 kton Water Cherenkov detector (MEMPHYS) located at a baseline of 130 km in the Fr\'ejus site. The neutrino fluxes simulation relies on a new GEANT4 based simulation coupled with an optimization algorithm based on the maximization of the sensitivity limit on the $\theta_{13}$ mixing angle. A new configuration adopting a multiple horn system with solid targets is proposed which improves the sensitivity to $\theta_{13}$ and the CP violating phase $\delta_{CP}$.Comment: 11 pages, 18 figures, 2 table

Mass production test of Hamamatsu MPPC for T2K neutrino oscillation experiment

In the T2K near neutrino detectors, about 60 000 Hamamatsu Multi-Pixel Photon Counters (MPPCs) will be used. The mass production of MPPC has started in February 2008.In order to perform quality assurance and to characterize each device, we have developed an MPPC test system. For each MPPC, gain, breakdown voltage, noise rate, photo detection efficiency, and cross-talk and after-pulse rate are measured as functions of the bias voltage and temperature. The design of the test system and the measurement procedure are described.Comment: Contribution to the proceedings of NDIP 2008, Aix-les-Bains, France, June 15-20, 200

Development and operational experience of magnetic horn system for T2K experiment

A magnetic horn system to be operated at a pulsed current of 320 kA and to survive high-power proton beam operation at 750 kW was developed for the T2K experiment. The first set of T2K magnetic horns was operated for over 12 million pulses during the four years of operation from 2010 to 2013, under a maximum beam power of 230 kW, and $6.63\times10^{20}$ protons were exposed to the production target. No significant damage was observed throughout this period. This successful operation of the T2K magnetic horns led to the discovery of the $\nu_{\mu}\rightarrow\nu_e$ oscillation phenomenon in 2013 by the T2K experiment. In this paper, details of the design, construction, and operation experience of the T2K magnetic horns are described.Comment: 22 pages, 40 figures, also submitted to Nuclear Instrument and Methods in Physics Research,

Drift field generation with Cockcroft-Walton voltage multiplier in xenon gas for AXEL 0vββ search detector

16th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2019) 9-13 September 2019, Toyama, JapanFor noble gas Time Projection Chambers (TPCs) in the field of rare event searches, operation of high voltage to generate an electric field is a key point. We designed a new structure of electrodes to shape a strong and uniform drift field without electric discharge, in which electrodes of two different radius are used. We also developed Cockcroft-Walton voltage multiplier as a high voltage generator inside a pressure vessel. We achieved −30.0 kV output and examined such kind of voltage generator is feasible as a high voltage supplier in a TPC

Design and performance of a high-pressure xenon gas TPC as a prototype for a large-scale neutrinoless double-beta decay search

A high-pressure xenon gas time projection chamber, with a unique cellular readout structure based on electroluminescence, has been developed for a large-scale neutrinoless double-beta decay search. In order to evaluate the detector performance and validate its design, a 180~L size prototype is being constructed and its commissioning with partial detector has been performed. The obtained energy resolution at 4.0~bar is 1.73 $\pm$ 0.07% (FWHM) at 511 keV. The energy resolution at the $^{136}$Xe neutrinoless double-beta decay Q-value is estimated to be between 0.79 and 1.52% (FWHM) by extrapolation. Reconstructed event topologies show patterns peculiar to track end-point which can be used to distinguish $0\nu\beta\beta$ signals from gamma-ray backgrounds.Comment: 24 pages, 25 figures, 1 table. Preprint paper for PTE