Prof. Hiroyasu Tajima Receives the FY2026 Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology (Research Category)

2026-04-17

Award Announcement
Professor Hiroyasu Tajima of the Institute for Cosmic Ray Research Receives the FY2026 Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology (Research Category)

Title of Achievement
“Research in Particle and Astroparticle Physics through the Development of Silicon Detectors”

Achievement
For many years, gas detectors and scintillation detectors have served as the primary tools in the fields of accelerator-based particle physics and cosmic observations. Amidst this background, semiconductor detectors—which offer theoretically superior position and energy resolution—were highly anticipated as the technology that would realize the next generation of precision measurements.
Prof. Tajima has vigorously driven the design and development of innovative silicon semiconductor detectors and their signal processing circuits, overcoming numerous technical hurdles. The detectors developed under his leadership have played a central role in several large-scale projects, including the Belle Experiment at the High Energy Accelerator Research Organization (KEK), NASA’s Fermi Gamma-ray Space Telescope, and JAXA’s X-ray astronomy satellite Hitomi.
• The Belle Experiment: Successfully conducted the world’s first precision verification of the “violation of matter-antimatter symmetry” predicted by the Kobayashi-Maskawa theory.
• The Fermi Telescope: Elucidated the mechanism of “cosmic-ray acceleration” in supernova remnants and verified the “invariance of the speed of light” using distant gamma-ray bursts.
• The Hitomi Satellite: Achieved high-precision measurements of “gamma-ray polarization from the Crab Nebula.”
Prof. Tajima’s contributions were indispensable to the realization of these scientific milestones.
Furthermore, extending beyond fundamental science, the results of this research have been commercialized as high-sensitivity gamma-ray cameras capable of visualizing radioactive substances. By detecting materials such as cesium with high sensitivity and mapping their distribution, this technology has improved the efficiency of decontamination efforts. It is widely expected to contribute to the ongoing safety and security of society.