Neutrinoless double-beta decay

Einstein's theory of relativity explains how matter can be created from energy - but every process we've seen generates equal amounts of matter and antimatter. As we live in a universe overwhelmingly dominated by matter, this leads to one of physics' biggest mysteries - how was the matter-antimatter asymmetry generated?

Neutrinoless double-beta decay (0νββ) could provide an explanation. It’s a proposed radioactive decay that would create matter (electrons) without antimatter. If it exists, it could not only give a clue to the origin of the universe but to another long-standing particle-physics mystery – why, contrary to the Standard Model, do neutrinos have mass? Neutrinoless double-beta decay would only be possible if neutrinos get their mass through the “Majorana mechanism”, meaning that they are their own antiparticles. This theory could also give a very nice explanation to another mystery - why neutrinos’ masses are so much smaller than those of other fundamental particles - but we don’t yet know whether it’s true. An observation of neutrinoless double-beta decay would be proof that neutrinos are Majorana particles.

We know that if 0νββ does exist, it has a very long half-life – trillions of times longer than the age of the universe – so we need very clean, low-background detectors if we want a chance of seeing it. Edinburgh is looking for 0νββ using the SuperNEMO detector.