E. Ichihara

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.

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.

Search for Proton Decay via {ital p} {r_arrow} {ital e}{sup +}{ital {pi}}{sup 0} in a Large Water Cherenkov Detector

報告番号: 乙14530 ; 学位授与年月日: 2000-01-24 ; 学位の種別: 論文博士 ; 学位の種類: 博士(理学) ; 学位記番号: 第14530号 ; 研究科・専攻: 理学系研究科We have searched for proton decay via p{r_arrow}e{sup +}{pi}{sup 0} using data from a 25.5 kton{center_dot}yr exposure of the Super-Kamiokande detector. We find no candidate events with an expected background induced by atmospheric neutrinos of 0.1thinspthinspevents. From these data, we set a lower limit on the partial lifetime of the proton {tau}/B{sub p{r_arrow}e{sup +}{pi}{sup 0}} to be 1.6{times}10{sup 33} years at a 90{percent} confidence level. {copyright} {ital 1998} {ital The American Physical Society }