Albert Einstein Center for Fundamental Physics

AEC Particle Trail


Muon Neutrino Sign at Grosse Schanze

Muon neutrinos are, like all neutrinos, very feebly interacting particles: they can cross the entire thickness of the Earth undisturbed.

They are usually produced in weak interactions involving a muon. In physics experiments, we can detect them by observing other particles produced in the rare case of a neutrino interaction, or by inferring their presence if we conclude that an undetected particle (the neutrino) must have carried away energy.

Neutrinos have a very small mass and we have not been able to measure it directly yet. Their mass is also theoretically a challenge. We observe that neutrinos "oscillate" when they travel through space, they change their flavour (for example, an electron neutrino can oscillate into a muon neutrino). This phenomenon can be observed, for example, in a deficit of expected number of electron neutrinos from the sun (solar neutrino problem). For this mechanism to work, neutrinos must have mass. However, how this mass is generated still needs to be fully understood and implemented in the Standard Model of particle physics.

Muon neutrinos are particularly well suited for laboratory experiments and the AEC of the University of Bern is heavily involved in a number of them. The DUNE experiment, for example, measures neutrinos that travel about 1300 km through the Earth's crust.