Study of high energy atmospheric and astrophysical neutrinos by a large water Cherenkov detector

1)我们建立了一种利用FADC记录的PMT脉冲形状信息重建SK全含（FC）事件可见能量的新方法。我们将该方法应用于SK2 FC大气中微子样品，发现由于ADC的溢出，常规的ADC可见能量最多被低估了约2倍。2)我们通过多次切割制作了SK2 FC大气中微子样品中的电荷电流相互作用的富集样品，并根据FADC数据获得了正确的大气中微子能量分布。这是继FREJUS在10 GeV以下进行实验后，首次在多十分能区测量大气大气能谱。在100 GeV以上的区域没有发现任何事件。与大气通量计算的预测值0.3一致。3)上述结果由名古屋大学的硕士论文（T. Koike 2006）总结，并在2006年秋季和2007年春季的JPS会议上报告。7.4)完成了FADC对SK2和SK3的校准工作。改进了FADC的分析程序和MC代码。5)改进的上行子候选子FADC触发器的设计研究。我们了解到这需要对超级神冈外探测器的DAQ电子设备进行实质性的改变。6)利用超高速定时脉冲N2激光系统测试了用于SK内探测器的20英寸PMT在高光子输入下的线性度。我们观察到，在输入时，它显示出良好的线性，高达700 p.e.。7) 2005年12月27日SGR1806-20最大耀斑的中微子在ICRC2005中被搜索和报道。我们还利用上升的μ子事件研究了天体物理中微子，并在期刊和会议论文集上发表了论文。此外，我们还研究了与本工作相关的牛脑带电电流和牛脑带电电流的识别。它们也被出版了。

1) We have established a new method to reconstruct visible energy of fully-contained (FC) events at SK by using PMT pulse shape information recorded by FADC. We applied this method to SK2 FC atmospheric neutrino sample and found conventional visible energy using ADC was underestimated by about factor 2 at most because of overflow of ADC.2) We have made an enriched sample of charged current nue interactions in SK2 FC atmospheric neutrino sample by applying several cuts and obtained a correct energy distribution of atmospheric nue based on FADC data. This is the first measurement of energy spectrum of atmospheric nue in the multi-10th energy region after the FREJUS experiment did at below 10 GeV. No event was found in more than 100 GeV region. It is consistent with 0.3 expected from atmospheric nue flux calculation.3) These results shown above was summarized in a master thesis of Nagoya University (T. Koike 2006) and reported in JPS meetings in autumn 06 and spring 07.4) Calibration work of FADC for SK2 and SK3 was done. Analysis program and MC codes for FADC were improved5) Design study of improved FADC trigger for up-going muon candidates. We leaned it requires substantial change in DAQ electronics of the outer detector of Super-Kamiokande.6) Linearity of 20-inch PMT used in the SK inner detector at very high photon input was tested by using a very fast timing pulsed N2 laser system. We observe it shows good linearity up to 700 p.e. at input.7) Neutrinos from the largest flare of SGR1806-20 at Dec27, 2005 were searched and reported in ICRC2005. We also have studied astrophysical neutrinos by using up-going muon events and published papers in refereed journals and conference proceedings. Also we have studied identification of nutau charged current events and nue charged current events related to this work. They were also published.