Mourning for Dr. Yoji Totsuka - School of Science, the University of Tokyo
Aug 19, 2008

Mourning for Dr. Yoji Totsuka

Sachio Komamiya (Professor, Physics)

At 2:50 on July 10, 2008, Dr. Yoji Totsuka, an honorary professor emeritus of the University of Tokyo passed away. The funeral service was held in Aoyama Sogisho on July 12 and attended by a large number of people from every sector of society, which proved Dr. Totsuka's popularity.

Dr. Totsuka was born in Fuji City, Shizuoka Prefecture. After completing his B.S and M.S in physics at the University of Tokyo, he received a PhD from the Graduate School of Science, the University of Tokyo, under the supervision of Dr. Masatoshi Koshiba for research on cosmic ray muon bundle flux at Kamioka mine, which made him get involved with Kamioka.

After earning a PhD in 1972, Dr. Totsuka became a research associate at School of Science, the University of Tokyo and participated in the research on DASP experiment at the newly-constructed DORIS (electron-positron collider) at DESY (Deutches Elektoronen Synchrotron) in Hamburg, Germany. In 1974, J/ψ (charm quark) was discovered at BNL (Brookhaven National Laboratory) and at SLAC (Stanford Linear Accelerator Center), which enabled elementary particle physics to move to a new era. Unfortunately, DORIS was operated by the energy a little higher than the energy that produces J/ψ, which means DORIS missed the big discovery. However, the late Dr. Shuji Orito and Dr. Totsuka discovered a new particle (Pc) that belongs to J/ψ group.

At DESY, construction of PETRA (an electron-positron collider) was being developed followed by DORIS and Dr. Totsuka returned to Japan and stayed for 3 years to make preparations for JADE experiment at DESY. He went to Germany again before the JADE experiment began and lived in Germany with his family for 6 years and a half in total. At PETRA, Dr. Totsuka experimentally established quantum electrodynamics with high precision at the highest energy of the time and performed a search for super-symmetry partner of electron.

In 1981, Dr. Totsuka came back to Japan in order to establish the Kamiokande experiment (Kamioka Nucleon Decay Experiment) proposed by Dr. Koshiba. Together with Dr. Koshiba, Dr. Totsuka, leading a lot of researchers, completed the Kamiokande experiment using the advanced technology cultivated through accelerator experiments.

The most important purpose of the Kamiokande experiment was proton decay search. Due to the redundant (highly functional) design of the detector, however, low-energy neutrino could also be detected. And this function made it possible for the research team to detect neutrinos from Supernova SN1987, which led to Dr. Koshiba's winning of the Nobel Prize. In addition, the research team began to realize that atmospheric neutrino and solar neutrino were fewer than the amount predicted by the Standard Model. The first publication on atmospheric neutrino anomaly was published in 1988 but the research community would not acknowledge it. Dr. Totsuka wrote later that he had a hard time then.

At the beginning of the 1990's, Dr. Totsuka took over Dr. Koshiba's position as the spokesperson of Super-Kamiokande experiment, a successor of the Kamiokande experiment and established an experiment facility. In 1998, he and his colleagues demonstrated to the world with dramatically improved accuracy that atmospheric neutrino anomaly is due to neutrino oscillations. This was a breakthrough that proved the fact that neutrino has non-zero but tiny mass, although the Standard Model of particle physics said neutrinos were massless.

Even after becoming the director of ICRR (Institute for Cosmic Ray Research, the University of Tokyo), Dr. Totsuka worked as the director of Kamioka Observatory and led his team from the front in Kamioka. In 2000, he developed colorectal cancer and underwent surgery. Soon after that, in 2001, most of the photomultiflier tubes at Super-Kamiokande were destroyed due to an accident. Still recovering from his illness, however, Dr. Totsuka led his team in order to clarify the reason for the accident and establish recovery plans. After he made the famous comment to the world "We will rebuild the detector. There is no question.", he restored the facility back to normal.

In 2003, Dr. Totsuka became the director-general of KEK (High Energy Accelerator Research Organization) and directed J-PARC, the joint project between KEK and Japan Atomic Energy Agency in Tokai-mura, Ibaraki Prefecture, and promoted the future plan of global high energy experiment such as International Linear Collider. The spectacular T2K (Tokai to Kamioka) Experiment through which neutrinos were shot from J-PARC, Tokaimura to Super-Kamiokande, Kamioka deserves his name, To-tsu-ka.

In 2006, Dr. Totsuka's cancer spread to his lung and he quit his job at KEK after 3 years work. Despite his illness, he took up a post as the director of Research Center for Science Systems at JSPS (Japan Society for the Promotion of Science) and kept making sharp proposals on academic researches in Japan till his last moment.

Dr. Totsuka received many awards for the discovery of neutrino oscillations, etc.; Nishina Prize, Purple Ribbon Medal, the Order of Culture, the Franklin Institute Awards (USA), Rossi Prize (American Astronomical Society), Panofsky Prize (American Physical Society), Bruno Pontecorvo Prize (Russia), EPS Special Prize (European Physical Society), and so on. As reported by the media, he was one of candidates for the Nobel Prize.

Dr. Totsuka was an assistant leader of the karate circle when he was an undergraduate and became an advisor of the karate circle when he was working as a faculty member of the University of Tokyo. He was fond of the drink, liked to stroll in the fields of Kamioka, and loved plants. Although he took an all-or-nothing approach toward research, he had a good sense of humor. He fostered many researchers after him.

We feel heart-breaking grief for losing one of the world's leading physicists. We also would like to show our respect for Dr. Totsuka's struggle with his illness till his last moment and for his family's dedicated support.

We wish to convey our deepest sympathies.

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