H. Okazawa

Atmospheric muon-neutrino / electron-neutrino ratio in the multiGeV energy range

Abstract Data from the Kamiokande detector were used to study the atmospheric (v μ + v μ ) (v e + v e ) ratio in the multi-GeV energy range. The observed ratio of μ-like to e-like events relative to the calculated ratio, ( μ /e) data /( μ /e) MC = 0.57 -0.07 +0.08 ± 0.07, suggests that the atmospheric (v μ + v μ ) (v e + v e ) ratio is smaller than expected for these neutrino energies. Also studied was the zenith-angle dependence of the above ratio. Results of an analysis of neutrino oscillations are presented.

Measurement of the flux and zenith angle distribution of upward through going muons in Kamiokande II + III

The flux of upward through-going muons of minimum (mean) threshold energy > 1.6 (3.0) GeV is measured, based on a total of 372 events observed by the Kamiokande II+III detector during 2456 detector live days. The observed muon flux was (1.94+-0.10(stat.)+0.07-0.06(sys.))*10^-13 /cm^2/s/sr, which is compared to an expected value of (2.46+-0.54(theo.))*10^-13/cm^2/s/sr. The observation is in agreement with the prediction within the errors. The zenith angle dependence of the observed upward through-going muons supports the previous indication of neutrino oscillations made by Kamiokande using sub- and multi-GeV atmospheric neutrino events.

DEVELOPMENT OF HIGH SENSITIVITY RADON DETECTORS

High sensitivity detectors for radon in air and in water have been developed. We use electrostatic collection and a PIN photodiode for these detectors. Calibration systems have been also constructed to obtain collection factors. As a result of the calibration study, the absolute humidity dependence of the radon detector for air is clearly observed in the region less than about 1.6 g/m3. The calibration factors of the radon detector for air are 2.2

A study on the eμ identification capability of a water Čerenkov detector and the atmospheric neutrino problem

0.2 (counts/day)/(mBq/m3 )a t 0.08 g/m3 and 0.86

Search for Proton Decay via

0.06 (counts/day)/(mBq/m3) at 11 g/m3. The calibration factor of the radon detector for water is 3.6

p \rightarrow \nu K^{+}

0.5 (counts/day)/(mBq/m3). The background level of the radon detector for air is 2.4

using 260 kiloton

1.3 counts/day. As a result, one standard deviation excess of the signal above the background of the radon detector for air should be possible for 1.4 mBq/m3 in a one-day measurement at 0.08 g/m3. ( 1999 Elsevier Science B.V. All rights reserved. PACS: 29.40.-n

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Abstract We carried out an experimental test of various characteristics of a water Cerenkov detector, especially the particle identification capability, using the 12-GeV proton synchrotron at KEK, Japan. The detector characteristics so far studied are well reproduced by the Monte Carlo simulation. Especially it is able to identify electrons and muons with mis-identification probabilities less than a few percent in the momentum range of 250–1000 MeV/c except the particle positions in the extreme edge of the detector volume. Based on the present results, the deficiency of μ-neutrinos in the atmospheric neutrinos is not an artifact caused by some peculiar detector characteristics.

year data of Super-Kamiokande

We have searched for proton decay via p→νK+ using Super-Kamiokande data from April 1996 to February 2013, 260 kiloton•year exposure in total. No evidence for this proton decay mode is found. A lower limit of the proton lifetime is set to τ/B(p→νK+)>5.9×1033 years at 90% confidence level.

Study of neutron background in the atmospheric neutrino sample in Kamiokande

Abstract Neutron background in the atmospheric neutrino sample was studied based on the vertex position distribution of the fully contained π 0 events. No evidence for the background contamination was observed. The neutron contamination in the sub-GeV e-like sample was less than 1.2% at 90% C.L.