Neutrinoless double beta decay is a hypothetical nuclear process that, if observed, would reveal that neutrinos are their own antiparticles—a type of particle known as a Majorana particle.
In regular double beta decay, two neutrons in a nucleus transform into two protons, emitting two electrons and two antineutrinos. This rare process has been observed in certain isotopes. However, in neutrinoless double beta decay, no neutrinos are emitted. Instead, the antineutrino produced at one decay point would be immediately reabsorbed as a neutrino at another, possible only if neutrinos and antineutrinos are the same particle.
If detected, neutrinoless double beta decay would have profound implications:
- It would violate lepton number conservation, a key principle in the Standard Model.
- It would confirm that neutrinos are Majorana particles.
- It could help explain why neutrino masses are so small.
- It would support theories like leptogenesis, which link neutrino properties to the matter-antimatter imbalance in the universe.
Many experiments, such as GERDA, EXO, and LEGEND, are searching for this rare decay. So far, no confirmed observation has been made, but even setting limits on its rate helps constrain models of particle physics and cosmology.