Observation of a Small = e Ratio of Atmospheric Neutrinos in Super-Kamiokande by the Method of Particle Identi cation

Acknowledgements I would like to express my sincere appreciation to my advisor, Prof.Y.Totsuka, for introducing me this experiment and encouraging me throughout this work. I gratefully acknowledge the helpful advice of Prof. They are experts in the atmospheric neutrino analysis. Their suggestions and advices were very useful for me. I owe thanks to my fellow graduate students Y. They gave me useful discussions and assisted with my analysis. Without their supports, I could not accomplish my thesis. They gave me useful discussions about experimental details. I with to express my deeply appreciation to T.Hayakawa and Y.Koshio. They live i n Kamioka and supported me on various occasions. I would like to thank Prof. gave me many advices. I must also thank the staa of the KEK. I learned a lot about the experimental technique there. Prof.K.Nishikawa and Dr.A.Sakai gave me many useful suggestions and discussions. I would like to express my appreciation to Dr.Y.Oyama for his advice and support. His excellent guidance and suggestions were very useful for me. I would like to thank C.Mauger for reading and xing this manuscript. I thank the cooperation of Kamioka Mining and Smelting Company and nancial support of the Japan Society for the Promotion of Science.