Physicists from Mainz University Participate in JUNO

The construction of the facilities for the JUNO neutrino experiment has been initiated with an official groundbreaking ceremony near the south Chinese city of Jiangmen, attended by representatives from more than fifty partnering institutions from China, the US and Europe. Starting in 2020, the Jiangmen Underground Neutrino Observatory (JUNO) will begin to produce new information about the particle characteristics of the neutrino.

"The aim of JUNO is to precisely measure the oscillations of neutrinos for the purpose of investigating one of the major issues in neutrino physics today – the sequence or hierarchy of neutrino masses," explained Professor Michael Wurm of the Institute of Physics at Johannes Gutenberg University Mainz (JGU), one of the assigned German JUNO partners who watched the start of work on the underground lab.

There are three different types of neutrinos – electron, muon, and tau neutrinos. They can change from one type to another, a phenomenon known as neutrino oscillation. It is possible to determine the mass of the particles by studying the oscillation patterns.

"Oscillations only occur because neutrinos have three different masses. But which is the lightest of the three and which is the heaviest? The JUNO experiment will be sensitive enough to allow us to clearly sequence the three neutrino types," said Wurm. The particle physicist, who is also participating in the Borexino experiment that investigates solar neutrinos and is located under Italy's Gran Sasso mountain, sees this as an important step forward for the experimental efforts to find a violation of matter/antimatter symmetry in neutrino oscillations. Scientists hope to find out why matter and antimatter did not completely annihilate one another after the Big Bang.

It will only be possible to determine the sequence of neutrino masses through tiny changes in the oscillation patterns that cannot be detected by currently running experiments. The JUNO detector is thus being built in its own underground lab, which is located some 50 kilometers from two reactor complexes on China's southern coast.