A Tribute to Sachio Komamiya

| 8 July 2024

Portrait of Sachio Komamiya taken in 2013 when he was appointed as LCB Chair

With deep sadness, we announce the passing of Professor Sachio Komamiya, a prominent figure in the Japanese and international ILC community. He passed away on 5 June at the age of 71.

Born in Yokohama, Japan, in 1952, Komamiya graduated from the University of Tokyo in 1976. He went on to the Graduate School of Science, the University of Tokyo, and studied under Prof. Masatoshi Koshiba, the 2002 Nobel Laureate in Physics. 

Komamiya began his diverse international career by connecting with Germany. Koshiba proposed an experiment using PETRA, an electron-positron collider at DESY in Germany, in collaboration with Heidelberg University and Manchester University. This collaboration led to the JADE experiment collaboration, representing Japan, Deutschland (Germany), and England. Koshiba’s laboratory took charge of developing the lead-glass electromagnetic shower detector for the experiment, which operated reliably and contributed to numerous achievements, including the discovery of gluons.

During his second year in a PhD program, Komamiya relocated to Germany. After obtaining his PhD for his work at DESY, he took up a postdoc position at the University of Heidelberg, joining the group of Prof. Joachim Heintze in the JADE experiment. “He very quickly integrated himself into the group and the JADE experiment in general. Not only an excellent scientist and much appreciated colleague, he even showed a remarkable understanding of our German sense of humor,” said Rolf Heuer, former Director General at CERN. In his final lecture at the University of Tokyo, Komamiya reflected on his time in Germany, dedicating three slides to the jokes and pranks he and his colleagues enjoyed there. “As a physicist, Sachio was a pioneer. At DESY, he was one of the first to perform searches for supersymmetric (SUSY) particles, and his enthusiasm for this type of analysis earned him the nickname SachiNo,” Heuer added. Komamiya led the world’s first systematic search for groups of SUSY particles—a pursuit that continues at the Large Hadron Collider (LHC). Additionally, he made significant contributions to research efforts focused on the Higgs boson.

In 1986, His enthusiasm for the highest-energy experiments led him to move to the Stanford Linear Accelerator Center(SLAC)in the U.S. as a staff physicist. The construction of the new machine, the SLAC Linear Collider (SLC), the first linear collider, was underway there. The SLC was a single-pass collider that used the linac to accelerate both electrons and positrons, a design that was highly complex. Arcs at the end of the linac bend the beams, and a final set of optics focuses the beams down to a radius of 2-3 microns at the interaction point, achieving a center-of-mass collision energy of approximately 92 GeV to produce the Z0 particle. Komamiya worked on developing the arcs that bend the beams, one of the most complicated parts of the machine. 

Physics measurements at the SLC started in 1988 with the Mark II detector. “Although we met countless times at conferences and workshops (in particular in smoking corners) we worked only once together, in the MarkII experiment,” recalls Francois Le Diberder, Laboratory of the Linear Accelerator (LAL), France. Beside work in the wonderful SLAC for nearly two years, we enjoyed regular end of the week beer&smoking-workshops, mostly at his wife’s kitchen.Sachio laughed endlessly at my ability not to even notice  the huge celebration-party in SLAC for the first Z0 produced by e+e- annihilation,that I missed completely, to my dismay,” he said.

The Mark-II experiment achieved several significant successes, such as the discovery of Tau lepton and the precision measurement of the Z boson. In October 1989, the San Francisco Earthquake caused considerable damage in the San Francisco Bay Area, but SLAC managed to avoid severe damage. However, it disrupted the Mark-ll experiment, and Komamiya decided to move on to the next challenge.

Komamiya’s enthusiasm for the highest-energy experiment made him move to to Europa in 1990, joining the OPAL experiment at the Large Electron Positron Collider(LEP)at CERN. “Sachio was one of the first scientists to work in a large international collaboration at CERN on the OPAL detector”, said Lyn Evans, former project Leader for LHC, and the director of the Linear Collider Collaboration. “He learned the value of global collaboration in science. Sachio was an outstanding physicist and a great friend. His passing brought great sadness,” Evans shared. Tatsuya Nakada, Chair of the ILC International Development Team (IDT) also met Komamiya at CERN. “My encounter with Sachio took place when he was one of the major players in the OPAL experiment. I was particularly impressed by the clarity of his plenary presentation at the International Europhysics Conference on High Energy Physics in Brussel in 1995”, said Nakada,

Komamiya returned to Japan in 1999 and became a Director of the International Center for Elementary Particle Physics (ICEPP) at the University of Tokyo in 2000. While leading research and experiments there, Komamiya led Japan’s high-energy community. He served three terms as the chairman of the Japan Association of High Energy Physics (JAHEP).

His leadership and extensive international experience have been precious in advancing the ILC project. He was a Japanese representative for the International Committee for Future Accelerators (ICFA) from 1999.  In December 2012, the Global Design Effort (GDE) led by Barry Barish and the Research Directorate (RD) led by Sakue Yamada, both organisations responsible for leading the ILC R&D activities, completed their missions with the finalisation of the technical design report (TDR). At the same time, the ILC Steering Committee (ILCSC), which supervised the GDE and RD, also completed its mission. The batons were transferred to new organisations in 2013: the Linear Collider Collaboration (LCC), led by Lyn Evans for project development, and the Linear Collider Board (LCB), which oversaw LCC’s activity chaired by Komamiya. “He was a strong advocate for the ILC, eager to see it become Japan’s first globally hosted project,” Evans recalls. “I was very fortunate to witness how energetically he was steering the ILC activities as the first chairperson of the LCB. When I started getting involved with the ILC closer, Sachio was one of the most valuable partners for discussion,” Nakada affirmed.

Komamiya served as a diplomat to advance the ILC as a global project. “From the work and political perspective, I recall Sachio’s very helpful explanations of all the many different people and organisations who had a part in planning the ILC in Japan. I was always amazed that he could remember all the names and how they connected to each other,” said Andy White, Professor at the University of Texas, U.S.A. “Coming from outside Japan, it is not easy to understand Japanese politics at the national and local levels and all the other industrial and community entities having an interest in the ILC. I greatly appreciated Sachio’s calm and patient explanations of the often complex relations involved. Sachio fulfilled a critical and essential role bridging the areas of science and politics – a talent that we sorely miss”.

Sachio Komamiya with Masako Shiota (second from left) and other conference secretaries at LCWS 2013 held at University of Tokyo. Image credit: KEK

“As far as I have ever known, there is no other person whose personality was so loved by all the people around him, including particle physicists in Japan and abroad,” said Masako Shiota, a secretary at ICEPP who worked with Komamiya for 7 years. “I believe this is attributed to his enthusiasm for his research, his firm yet kind nature, and the charisma infused into every word he spoke.”

He wrote in his guest article for the ILC NewsLine, published in December 2013, “Since the ILC is a truly international project, the whole community has to possess a common vision of the science and the project.”. Perhaps it’s time to carefully consider his words once again.

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