A giant experiment to study neutrinos

On July 31, the Hyper-Kamiokande collaboration, which brings together 22 countries, including France, completed excavation in Japan of the cavern that will house a giant detector, 600 meters underground in a former mine. Filled with pure water and covered with light detectors, this instrument will observe the behavior of light, fleeting particles, neutrinos, and their mirror particles, antineutrinos, after a long journey through Earth.

These measurements may shed light on why antimatter disappeared in favor of matter at the beginning of the universe's history. The first experiments are expected to begin in 2028. With Hyper-Kamiokande, Japan hopes to win a third Nobel Prize related to this elementary particle whose properties, including its mass, remain largely mysterious.

In 2002, Masatoshi Koshiba received the famous prize for the Kamiokande experiment, which demonstrated the existence of neutrinos produced in cosmic reactions, such as the explosion of supernova SN1987A in 1987. Takaaki Kajita was awarded the prize in 2015, thanks to the Super-Kamiokande experiment, which measured the oscillation of neutrinos, that is, their transformation from one family of particles into another.

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