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[Welcome to the IPNS] Interview with Dr. Yoshikazu Nagai of the Neutrino Group
May 7th, 2026
In April 2026, Dr. Yoshikazu NAGAI joined the Neutrino Group at IPNS as an associate professor.
We interviewed him about what sparked his interest in the world of particle physics, the research he has conducted, and how he refreshes his mind when faced with challenges in his work.
■What sparked your interest in particle physics?
When I was a senior undergraduate student, I had the chance to take a seminar course taught by a professor of neutrino physics who was visiting our university for one year. That was when I first thought, “Particle physics is really interesting.” I think that experience was what sparked my interest in the field.
Soon after that, I decided to focus on particle physics when applying to graduate schools. Looking back now, it feels a little strange, because before taking that seminar, I did not have any particular interest in particle physics. It really made me realize how important encounters and opportunities can be.
■What kind of research were you involved in before coming to KEK?
As a graduate student, I worked on the search for the Higgs boson in the CDF experiment at Fermilab’s Tevatron accelerator. At that time, the LHC was just about to start operation, and I remember working very hard, hoping that we might find some hint of the Higgs boson before the LHC did.
In the end, we did not find the Higgs boson before I completed my Ph.D., and I continued working on the same topic as a postdoctoral researcher. I moved to a research institute in Marseille, France, where I joined the ATLAS experiment at the LHC and continued the search for the Higgs boson. The Higgs boson was discovered during my first postdoctoral position, and that became a good opportunity for me to think about what to work on next. From there, I shifted my research focus somewhat toward neutrino physics.
After moving to the University of Colorado Boulder in the United States, I began working on research aimed at understanding neutrino beams with high precision. I built a detector, specifically a gas TPC detector, needed for precise measurements of hadron production, which produces the parent particles of neutrinos. We installed the detector in the NA61/SHINE fixed-target experiment at CERN, where we collected and analyzed data. I also worked on applying the measurement results from NA61/SHINE to improve the precision of neutrino beam predictions in the T2K experiment.
Before coming to KEK, I was at Eötvös Loránd University, or ELTE, in Budapest, Hungary. There, I launched a new research group mainly focused on improving the precision of our understanding of neutrino beams for the T2K experiment.
■What kind of research do you hope to pursue at KEK?
Based on my previous experience in neutrino beam research, I would like to contribute to the upcoming Hyper-K experiment. In particular, I hope to help provide a stable, high-intensity neutrino beam and understand its properties with unprecedented precision. By doing so, I would like to help lay the groundwork for the discovery of CP violation through neutrino oscillations, and for precise measurements of the CP phase, which are among the major goals of Hyper-K. Casually speaking, I hope to contribute to building the backbone, or foundation, of the Hyper-K experiment.
At the same time, I would also like to think about the future of neutrino physics beyond Hyper-K. It is still far from obvious what direction the field of neutrino physics should take in the longer term, or what KEK can do next as a host laboratory for neutrino physics. That is exactly why I would like to start thinking now about what needs to be prepared, and connect those ideas to future research.
■Can you share your method of refreshing your mind when facing difficulties in research and work?
I enjoy eating good food and drinking, so I like going out for a nice meal from time to time. I also enjoy buying good ingredients and drinks, and trying out different pairings at home. Spending time like that, feeling just a little bit luxurious, is something I really enjoy.
I also like spending time with my child, taking care of our small home vegetable garden together — although I am still very much a beginner — or going to the park and playing various activities together. Those moments are a very good way for me to refresh myself.
We look forward to your future activities at the IPNS!
