Toward First Detection of the Solar Mikheyev-Smirnov-Wolfenstein Transition with JUNO.

Matter-induced neutrino flavor mixing (the Mikheyev-Smirnov-Wolfenstein, or MSW, effect) is a central prediction of the neutrino mixing framework, but it has not been conclusively observed. Direct observation of the energy-dependent MSW transition in the solar electron-neutrino survival probability would solve this, but backgrounds have been prohibitive. We show that our new technique for suppressing muon-induced spallation backgrounds will allow JUNO to measure the MSW transition at >4σ significance in 10 years. This would strongly support upcoming multibillion-dollar next-generation experiments and their goals in cementing the neutrino mixing framework.