K. Kaneyuki

Indications of neutrino oscillation in a 250 km long-baseline experiment.

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Distillation of Liquid Xenon to Remove Krypton

A high performance distillation system to remove krypton from xenon was constructed, and a purity level

Commissioning of the new electronics and online system for the Super-Kamiokande experiment

The Super-Kamiokande (SK) detector is a ring imaging Cherenkov detector for neutrino physics and proton-decay search and consists of 50000 tons of pure water equipped with about 13000 photo-multipliers (PMTs). The old front-end electronics and online system running for more than one decade were all upgraded in September, 2008 and the data acquisition was started successfully. The new front-end electronics is based on a charge to time converter (QTC) and a multi-hit TDC. TCP/IP based readout channel is implemented to handle large amounts of data. In the new data acquisition (DAQ) scheme, the hardware event-trigger for the data reduction is replaced by processing all the hits in the online farm, so that we are able to lower the threshold of the detection energy for solar neutrino and analyze consecutive events whose time interval is too long to detect in the previous system. To make the new online system to be capable of processing larger dataflow of up to 470MB/s, we utilize Gigabit and 10Gigabit Ethernet techniques and distribute the load over Linux PCs to handle a large amount of data. In this paper, we will describe the design and performance of the new system in the commissioning.

Development of New Front-End Electronics for Super-Kamiokande

Super-Kamiokande is a ring imaging water Cherenkov detector for astro-particle physics that consists of 50 kton pure water and about 13000 photomultiplier tubes (PMTs). We are planning to upgrade all the front-end electronics in next year. By high speed signal processing electronics, we will record all the hits of all the PMTs without any hardware filtering, aiming observations of much fainter signals of the supernova relic neutrinos, lower energy (~3 MeV) solar neutrinos, neutrino burst from nearby galactic supernova, and so on. The energy resolutions of multi-GeV atmospheric neutrino events will also be improved by the electronics. The new front-end electronics is based on a charge to time converter (QTC) and a multi-hit TDC. TCP/IP based readout channel is implemented to handle large amounts of data. We have developed a custom ASIC QTC and evaluated the characteristics of the chip and the prototypical board; high-speed (1 MHz cycle), high sensitivity for single photo-electron signal, good charge (0.1 pC RMS) and timing (0.3 ns RMS) responses, and wide charge dynamic range (2500 pC). In this paper, the design and the performance of the front-end board are discribed.

The new front-end electronics for the Super-Kamiokande experiment

Super-Kamiokande is a ring imaging water Cherenkov detector for astro-particle physics that consists of 50 kton pure water and about 13000 photomultiplier tubes (PMTs). We are planning to upgrade all the front-end electronics in next year. By high speed signal processing electronics, we will record all the hits of all the PMTs without any hardware filtering, aiming observations of much fainter signals of the supernova relic neutrinos, lower energy (~ 3 MeV) solar neutrinos, neutrino burst from nearby galactic supernova, and so on. The energy resolutions of multi-GeV atmospheric neutrino events will also be improved by the electronics. The new front-end electronics is based on charge to time converters (QTCs) and multi-hit TDCs. TCP/IP based readout channel is implemented to handle large amounts of data. We have developed a custom ASIC QTC and evaluated the characteristics of the chip and the prototypical board; high-speed (1 MHz cycle), high sensitivity for single photo- electron signal, good charge (0.1 pC RMS) and timing (0.3 ns RMS) responses, and wide charge dynamic range (2500 pC). In this paper, the design and the performance of the front-end board are described.

Scintillation yield of liquid xenon at room temperature

The intensity of scintillation light emission from liquid xenon at room temperature was measured. The scintillation light yield at 1 � C was measured to be 0:64 � 0:02 (stat.) � 0:06 (sys.) of that at � 100 � C. Using the reported light yield at � 100 � C (46 photons/keV), the measured light yield at 1 � C corresponds to 29 photons/keV. This result shows that liquid xenon scintillator provides high light yield even at room temperature.

Development of New Data Acquisition Electronics for the Large Water Cherenkov Detector

To improve the sensitivity of the Super-Kamiokande detector for elementary particle and astroparticle physics, new data acquisition electronics are under development. For a new front-end electronics development, charge-to-time converter (QTC) has been developed as a custom application specified integrated circuit (ASIC). To record all the data continuously to search for much fainter events, the new front-end electronics will be faster and dead-time less and also improve the quality of data. The design of the front-end electronics and the QTC chip and their performances are shown.

International Scoping Study (ISS) for a future neutrino factory and Super-Beam facility

This report summarises the conclusions from the detector group of the International Scoping Study of a future Neutrino Factory and Super-Beam neutrino facility. The baseline detector options for each possible neutrino beam are defined as follows: 1. A very massive (Megaton) water Cherenkov detector is the baseline option for a sub-GeV Beta Beam and Super Beam facility. 2. There are a number of possibilities for either a Beta Beam or Super Beam (SB) medium energy facility between 1-5 GeV. These include a totally active scintillating detector (TASD), a liquid argon TPC or a water Cherenkov detector. 3. A 100 kton magnetized iron neutrino detector (MIND) is the baseline to detect the wrong sign muon final states (golden channel) at a high energy (20-50 GeV) neutrino factory from muon decay. A 10 kton hybrid neutrino magnetic emulsion cloud chamber detector for wrong sign tau detection (silver channel) is a possible complement to MIND, if one needs to resolve degeneracies that appear in the δ-θ13 parameter space.