Seeing what none have seen before - School of Science, the University of Tokyo
Oct 26, 2015

Seeing what none have seen before

Department of Physics — Asai Laboratory

Professor Shoji Asai
Department of Physics
School of Science


Professor Asai graduated from the Department of Physics at the University of Tokyo in 1990, then the School of Science Master’s Program in 1992 and the Ph.D. Science Program in 1995. In 2003 he became an associate professor at the University of Tokyo’s International Center for Elementary Particle Physics, and then an associate professor in the School of Science in 2007. He took up his current position in 2013.

“I’m often asked by various media sources if I was happy,” he says, “but the truth is I wasn’t so much happy as relieved.”

The Higgs boson—the so-called “God particle”—appeared one ten-billionth of a second after the Big Bang, filling the vacuum and giving all things mass. Collaborating with thousands of researchers throughout the world, a team of University of Tokyo scientists led by Professor Shoji Asai contributed to jo the experiment designed to track down this particle. The relief he felt came on July 4, 2012, following CERN near Geneva, Switzerland, announced “New particle discovered—could this be the Higgs boson?”

“Humanity has made a huge investment to open the new window into nature,  finally showed us the existence of a particle that we were sure had to exist.”

Professor Asai’s specialty is particle physics. The discovery of the Higgs boson was the establish of the Standard Model, a description of the components making up the natural world from the subatomic level, the smallest unit. It was also an event that the notable revolution or the paradigm shift in the particle physics.

The Higgs boson is a particle with a close relation to vacuum—it turns out that vacuum is not filled with “nothingness,” but rather something called a Higgs field. In the ultra-high-temperature environment immediately following the birth of space, a space that was not yet filled by the Higgs field, no particles had mass and all moved at the speed of light. As the temperature of our Universe fell there were changes in its energy due to phase transitions, and elementary particles obtained mass for the first time through their interaction with the Higgs field that developed in the vacuum. “Our target was “particles” before, but in the phase we’re in now we’re researching “vacuum” field instead,” Professor Asai says. “That’s the significance of the Higgs boson’s discovery, and what makes it such an innovation.”

The “vessel” that encompasses this vacuum field from the outside is space-time. Professor Asai’s current interest lies in finding how space-time was created, and how it affects the vacuum field and particles.

“At the LHC, we’re exploring the nature of supersymmetry in order to learn more about space-time. If this can be established, we will understand the dark matter that makes up around 25% of the universe. It will also answer questions about how space-time was created at the very beginning of the universe.” According to Einstein’s theory of general relativity, gravity is the result of warping in space-time. However, macro-level phenomena such as gravity and space-time cannot be explained when they are examined at the micro-level of quantum mechanics. “Humanity has not yet managed to bridge these macro and micro worlds,” says Professor Asai. “I want to find that bridge.”

The search is likely to be a long one, possibly requiring decades or even centuries. The Asai Laboratory has the mood of a place that’s taking on such a great challenge, but at the same time it is an enjoyable atmosphere, permeated with a field of fun, like a Higgs field permeates a vacuum. “When you’re trying to answer big questions, the most important thing is never giving up. Keeping at it requires that it’s enjoyable, though, so fun is an important element. I try to give my students both freedom and responsibility, and to note the importance of accumulated small victories. I want them to have those flashes of understanding as something to treasure as their own.” Professor Asai and his students have numerous conversations as they assist each other in their daily research.

“There’s a direct correlation between the amount of freedom we’re given and our responsibility for making progress,” says Akira Miyazaki (D3). “To me he feels less like a teacher, and more like a fellow researcher.”

Progress in science relies on researchers developing ideas that only they know. The Asai Laboratory is a place where students learn to uphold their freedom and responsibility while coming into contact with the cutting edge of research in particle physics.



CERN’s LHC is an enormous particle accelerator; one lap around the tunnel is a 27 km trip. The photo shows the ATLAS detector inside the LHC. This device, named after the Titan of Greek mythology, weighs 7500 tons, is 44 m long, and 24 m tall and wide. The detector sits at the proton–proton collision point, and is able to detect the type and movement path of particles spewing out from collisions with very high accuracy. Photo supplied by CERN.


Student Evaluations

“We’re given a huge amount of personal data storage and have access to good servers, which makes for a good working environment.” (Maya Okawa, M2)
“He lets us do as we please, but at the same time he watches out for us well. This is definitely a lab where students can rely on their teacher.” (Akira Miyazaki, D3)

― Office of Communication ―

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