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In a Japanese laboratory, scientists searched for traces of a mysterious particle that could explain strange results from old experiments.
In a vast, dark hall, they're searching for a single person who makes almost no sound. That's how physicists hunt for sterile neutrinos — ghostly particles that pass through matter, leaving barely a trace.
At Japan's J-PARC accelerator facility, the JSNS² experiment is probing an old mystery: in the 1990s, the American LSND experiment saw a hint of extra neutrinos that shouldn't exist. One explanation is the existence of a sterile neutrino, one that doesn't even participate in the weak interaction (the very force that makes the Sun shine).
The first data, collected in 2022, showed no extra particles. But the question can't be definitively closed — too few events have been recorded. The experiment continues, and a second detector has recently been built to catch neutrinos at a greater distance from the source.
Neutrinos are so elusive that billions of them fly through your body every second, and you never notice.
If sterile neutrinos do exist, it would turn physics on its head: they could be linked to dark matter and explain why the Universe has more matter than antimatter.