Continuous Observation of Solar Neutrinos and Detection of Supernova Neutrinos

神冈探测器（Kamiokande）是一个水切伦科夫探测器，位于东京大学宇宙射线研究所的神冈地下实验室。它是目前世界上正在工作的四个太阳中微子探测器中唯一的实时探测器。它还可以测量反冲电子的能量。由于这些特征，它的观测结果受到高度重视。1990年，神冈探测器进行了升级，例如，用新的高性能系统取代电子设备。然而，为了充分利用新的电子设备，还必须更新电源和数据采集系统;本研究计划的两个课题之一，神冈台的太阳中微子观测，是根据截至1993年7月已发表的观测资料得到的主要结果（相当于1 667个探测器使用日）总结如下。(1)观测到的来自^8B衰变的太阳中微子通量为： ...更多信息 大约是理论预期的50%。(2)反冲电子能谱可以用^8B衰变中微子谱来解释。(3)在实验不确定性范围内，白天和夜间的太阳中微子通量没有差别。(4)加上神冈Ⅱ号的观测，神冈Ⅱ号的观测时间为6年半，没有发现太阳中微子通量随太阳活动的变化而发生明显的时间变化。包括尚未公布的数据在内，截至2月底，神冈Ⅱ号的太阳中微子观测时间为2，140天。1995年，该研究项目的另一个主题是探测大质量恒星引力坍缩引起的超新星爆炸中的中微子爆发。虽然在研究期间没有发现中微子爆发，但我们得到了银河系恒星坍缩速率的世界最好上限，<-1>截至1993年11月为0.44年。应该指出的是，在本研究项目期间，在神冈号的监测系统中安装了一个在线、半实时中微子爆发监视器（每15分钟一次）。这使我们能够在光学观察之前发现银河系的日冕驱动的超新星爆炸。少

Kamiokande is a water Cherenkov detector which is located at the Kamioka Underground Laboratory of Institute for Cosmic Ray Research, University of Tokyo. It is the only realtime detector out of the four solar-neutrino detectors currently at work in the world. It can also measure the energy of recoil electrons. Because of these characteristic features, its observation results have been highly valued. In 1990, the Kamiokande detector was upgraded by, e.g., replacing electronics with a new high-performance system. In order to fully exploit the new electronics, however, power supplies and data-acquisition sytem had also to be upgraded ; this was achieved in 1991 supported by the present Grant-in-Aid.Main results of the Kamiokande's solar-neutrino observation, which is one of the two subjects of this research project, obtained from the published data up to July, 1993 (corresponding to 1,667 live detector days), are summarized as follows.(1) The observed solar neutrino flux from ^8B decay i … More s about 50% of theoretical expectations.(2) The recoil-electron energy spectrum is explained by the ^8B-decay neutrino spectrum.(3) There is no difference between the day-time and nighttime solar-neutrino fluxes within experimental uncertainties.(4) Together with the Kamiokande-II observation, a total of 6 years and a half Kamiokande's observation shows no appreciable time variation of the solar-neutrino flux associated with the variation of the solar activity.Including the data which are not yet published, the total Kamiokande's solar-neutrino observation amounts to 2,140 live detector days up to the end of February, 1995.The other subject of this research project is detection of neutrino bursts from supernova explosions due to gravitational collapse of massive stars. Though no neutrino burst was detected during the term of this research project, a world best upper limit of the stellar collapse rate in our Galaxy, 0.44 yr^<-1> as of November, 1993, has been obtained. It should be mentioned that an on-line, semi-realtime neutrino-burst watch (in every -15 minutes) has been installed in the Kamiokande's monitoring system during the term of this research project. This enables us to discover a Galactic collapse-driven supernova explosion before it is observed optically. Less