Physics related to the atmospheric neutrino anomaly

安田在二味、三味和四味框架下对大气中微子数据进行了分析，结果表明，在三种味的情况下，θ_&lt；13&gt；；是很小的，并且仍然允许有ν_μ[tautomer]ν_γ和ν_μ[tautomer]ν_S的一大类混合振荡。他还讨论了长基线实验和中微子工厂的现象学，并证明了物质效应可以增强CP破坏，中微子工厂的CP破坏信号在基线约3000公里和Muon能量50 GeV时得到优化。Minakata与安田一起研究了大质量中微子对无中微子双β衰变实验的影响，发现混合暗物质场景提出的具有几乎简并的大质量中微子的方案在无中微子双β衰变实验中不可避免地暗示着一个正信号。他还研究了在极低能量中等基线实验中测量CP破坏的可能性，并在三味框架下对超新星中微子进行了研究，表明在一定条件下，可以通过中微子与超新星的转换来区分倒置和正常的等级模式。Kajita作为Super-Kamiokande小组的领导人致力于对大气中微子的观测，他们得出结论，他们的数据可以被解释为中微子振荡的证据。这项工作不仅引起了物理学家的关注，也引起了媒体的关注。随后，他们获得了更多的数据统计数据，并排除了ν_μ[异构体]ν_S的情景。另一方面，Super-Kamiokande小组测量了太阳中微子，他们得出结论，大混合角的MSW溶液与数据最吻合。从我们的研究结果中，我们对大气中微子的质量平方差引起的中微子振荡有了更多的了解。

Yasuda worked on analysis of the atmospheric neutrino data in the frameworks of two, three and four flavors, and showed that θ_<13> is small in the three flavor case, and that a large class of the hybrid oscillations with ν_μ【tautomer】ν_γ and ν_μ【tautomer】ν_s is still allowed. He also discussed phenomenology of long baseline experiments and neutrino factories and showed that CP violation can be enhanced due to matter effects and that signals of CP violation at neutrino factories are optimized for the baseline approximately 3000km and the muon energy 50 GeV.Minakata worked on implications of massive neutrinos to neutrinoless double beta decay experiments with Yasuda and found that a scheme with almost degenerate massive neutrinos suggested by the mixed dark matter scenario inevitably implies a positive signal in neutrinoless double beta decay experiments. He also examined the possibility of measuring CP violation in very low energy medium baseline experiments, and he worked on supernova neutrinos in the three flavor framework and showed that inverted and normal hierarchy patterns can be distinguished under a certain condition by neutrino conversion from supernovae. Kajita worked on observation of atmospheric neutrinos as a leader of the Super-Kamiokande group and they concluded that their data can be interpreted as evidence of neutrino oscillation. This work has caught a lot of attention not only from physicists but also from the media. Subsequently they gained more statistics of the data and they excluded the ν_μ【tautomer】ν_s scenario. On the other hand, the Super-Kamiokande group measured the solar neutrinos and they concluded that the large mixing angle MSW solution gives the best fit to the data. From our research results we have gained much more knowledge on neutrino oscillations coming from the mass squared difference of the atmospheric neutrinos.