Professor Yoshitaka Ito Gives a Lecture at the University of Tokyo Fair “Learning Science” at LaLaport Kashiwanoha

　The University of Tokyo Fair “Learning Science,” a pre-event for the Kashiwa Campus Open Day, was held over two days on October 27–28 at LaLaport Kashiwanoha in Kashiwa City. From the Institute for Cosmic Ray Research, Professor Yoshitaka Ito, Director of the Research Center for Cosmic Neutrinos, gave a lecture titled “Messages from Space?! The Mystery of Ghost Particles!”

Professor Ito’s lecture was part of a special program called “Mystery Solving! Kids’ Science Exploration Team,” a collaborative project with Mitsui Shopping Park LaLaport Kashiwanoha, where faculty members from the University of Tokyo Kashiwa Campus visit and share fascinating topics not usually covered in school. About 20 families who registered in advance sat on mats laid out in Crystal Court, and along with walk-in attendees standing nearby, around 70 people listened attentively.

Professor Ito began by introducing a small device (about 10 cm square) that detects muons, a type of cosmic ray that comes from space. He explained, “You can observe cosmic rays passing through something the size of your palm about once per second.” He then described neutrinos—mysterious ghost particles—as one of the elementary particles that make up matter. Neutrinos are generated in places where nuclear fusion occurs, such as the sun, and are extremely light and rarely interact with other matter, allowing them to pass through the Earth and almost anything else. His explanations were easy to understand and included occasional quizzes.

He also talked about efforts to detect neutrinos through rare reactions in a massive underground water tank located in Hida City, Gifu Prefecture. He mentioned that the next-generation detector, Hyper-Kamiokande, is expected to be completed in a few years and showed photos of the newly constructed underground cavern. He pointed out that photomultiplier tubes (PMTs)—light sensors used to detect the faint Cherenkov light emitted by electrons scattered by neutrinos—were on display at the venue, encouraging attendees to “take a close look.”

After the 40-minute lecture, elementary school students in the audience asked questions such as “How big is a neutrino?”, “Will you die if hit by gamma rays?”, and “Do neutrinos disappear when they collide with water?” Professor Ito answered each question one by one.