Super-Kamiokande marks 30 years with 2.6-sigma hint of supernova neutrino background

Japan's Super-Kamiokande detector, holding 50,000 tonnes of ultra-pure water and over 11,000 photomultiplier tubes, has marked 30 years of operation. In June 2026 the collaboration reported a 2.6-sigma excess in the energy range expected for the diffuse supernova neutrino background. Its successor Hyper-Kamiokande should begin taking data around 2028.

• Detector holds 50,000 tonnes of ultra-pure water and more than 11,000 photomultiplier tubes
• June 2026 data showed a 2.6-sigma excess in the supernova neutrino background search
• Gadolinium sulfate has been added to the water since 2020 to suppress background
• Hyper-Kamiokande is expected to start collecting data around 2028