Progress in neutrino oscillation physics

对T2 K实验中的前探测器系统进行了详细的研究。T2 K是下一代中微子振荡实验。中微子由J-PARC加速器产生，并在Super-Kamiokande中检测到。实验将于2009年开始。这个实验的主要目标之一是寻找非零的θ_<13>，这是中微子混合角之一，目前还不知道。前端探测器应该能够预测中微子能谱和中微子味而不振荡。详细的Monte Carlo研究表明，在距离中微子产生靶约1.8km处，安装5000个20 cm直径的光电倍增管的水切伦科夫探测器应该具有足够高的性能，并对T2 K中微子束的未来可能性进行了研究。我们认为位于神冈和韩国的大型水切伦科夫探测器对中微子CP相位和质量等级的测量具有很高的灵敏度，并根据在Super-Kamiokande和K2 K中微子束事件中观测到的大气中微子事件对中微子振荡进行了研究。在中微子质量和混合角方面获得了各种新的结果。所有的结果都在标准中微子振荡框架下得到了解释。

A detailed study on the front detector system at the T2K experiment was carried out. T2K is a next generation neutrino oscillation experiment. Neutrinos are generated by the J-PARC accelerator and are detected in Super-Kamiokande. The experiment will start in 2009. One of the main goals of this experiment is the search for non-zero θ_<13>, which is one of the neutrino mixing angles and is not known yet. The front detector should be able to predict the neutrino energy spectrum and neutrino flavor without oscillation. Detailed Monte Carlo study concluded that a water Cherenkov detector with about 5000 20cm-diameter photomultipliers, located about 1.8km from the neutrino production target should have a sufficiently high performance for this experiment.In addition, future possibilities with the T2K neutrino beam were studied. It was concluded that large water Cherenkov detectors located in Kamioka and in Korea should have a very high sensitivity to the measurement of the neutrino CP phase and mass hierarchy.Studies of neutrino oscillations based on atmospheric neutrino events observed in Super-Kamiokande and K2K neutrino beam events were carried out. Various new results on neutrino masses and mixing angles were obtained. All the existing results are explained within the standard neutrino oscillation frame work.