Interview with Takaaki Kajita on 6 December 2015, during the Nobel Week in Stockholm, Sweden.

What’s your story? What brought you to science?

Takaaki Kajita: When I was a high school student, I learnt basic physics and I started to get interested in physics. Then I decided to learn physics in undergraduate and I learned that the physics was really interesting and I decided to learn more and therefore I joined Professor Koshiba’s group in the graduate course and I started the Kamiokande experiment. Actually, that was really the motivation for become a scientist.

Who was your most inspiring teacher?

Takaaki Kajita: The most inspiring teacher to me was Professor Koshiba. He essentially told me that we always have to have a new idea about the new researches and also we always think about the really important researches.

Describe your Nobel Prize-awarded work in one minute.

Takaaki Kajita: The work I was awarded to this Nobel Prize is based on studies of neutrinos produced by cosmic ray interactions in the atmosphere.  We observed that neutrinos passing through the earth are disappearing, well, half of them are disappearing, and this was concluded as the evidence for neutrino oscillations and therefore the evidence for the neutrino mass.

What motivated you to pursue your research?

Takaaki Kajita: In 1986 I was analyzing the Kamiokande data, almost accidently I found that there is a significant deficiency in the newer neutron events observed in Kamiokande. That was really surprising, and this was the motivation for me to continue studies of atmospheric neutrinos in the later 20 years.

Have you had a eureka moment?

Takaaki Kajita: Yes, again I think that eureka moment to me is the moment that we discovered the deficit of neutrino events in Kamiokande.

What’s the toughest challenge you’ve faced? How did you overcome it?

Takaaki Kajita: The hardest time in my research work was when the Super-Kamiokande was badly broken in 2001. In the end we were able to recover from this accident, but the most important ingredient to get the Super-Kamiokande back was the good leadership and also the good teamwork. The photomultiplier tubes used in Super-Kamiokande was broken, more than half of them were broken in about ten seconds. Why these photomultiplier tubes were broken? Well, we think that one of the photomultiplier tubes in Super-Kamiokande was broken spontaneously, then it generated a shockwave and this shockwave broke the adjacent photomultiplier tubes and then these photomultiplier tubes generated another shockwave breaking the other photomultiplier tubes and this was what happened in 2001. After that accident Super-Kamiokande collaboration decided to rebuild the detector and we worked together to recover the original configuration. It took several years to recover to the full configuration.

Watch the interview

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