Search for neutrino point sources in the southern sky hemisphere

我们利用超级神冈探测器探测到的中微子引起的向上的μ子，在南半球寻找天体中微子点源。寻找来自活动星系核（AGN）的中微子信号特别有趣。100 GeV以下的大气中微子起源的主要背景估计为0.05事件/年。从1996年到2001年，我们在1600天的探测器寿命中积累了大约2000个中微子引起的向上的μ子事件。我们在假设AGN中微子源的情况下，对中微子事件进行了蒙特卡罗模拟和解析计算。根据需要开发其他分析软件。我们花了大量的时间来开发超级神冈探测器中通过和停止μ子的自动事件重建程序。由大气中微子引起的向上运动的μ子的预期数量估计约为2000个事件，这与观测到的数量相当一致。我们将观测到的向上的μ子事件绘制在天体坐标上，并研究了事件的密度分布。我们检验了大气中微子背景事件中是否存在来自非天体点源的过量上升事件。然而，我们在南半球没有发现统计上显著的过剩。据此，我们对来自天体点源的中微子诱导上行μ子设定了最严格的上限10^<-14>/cm^2/s，置信水平为90%。

We search for celetial neutrino point sources in the southern sky hemisphere by neutrino induced upward-going muon detected with the Super-Kamiokande detector. Search for neutirno signal from active galactic nuclei (AGN) is particularly interesting. The major background of atmosperic neutrino origin below 100 GeV is estimated to be 0.05 events/year. We have accumulated approximately 2000 neutirino induced upward-going muon events during 1600 detector live days from 1996 to 2001. We perform a Monte Carlo simulation as well as an analytic calculation of neutrino events, assuming AGN neutrino sources. Other analysis software are developed whenever needed. We spend our time extensively on the development of an automatic event reconstruction program of through-going and stopping muons in the Super-Kamiokande detector. The expected number of upward-going muons induced by atmospheric neutrinos is estimated to be roughly 2000 events which is reasonably consistent with the observed number. We plot the observed upward-going muon events in the celestial coordinates and study the event density distribution. We check whether there exists excess of upward-going events from acelecial point sources againt the atmospheric neutrino background events. However, we find no statistically significant excess in the southern sky hemisphere. Accordingly, we set the most stringent upper limit of 10^<-14>/cm^2/s at 90% confidence level on neutrino-induced upward-going muons from celetial point sources.