Are neutrinos their own antiparticles? Is lepton number conserved? What is the neutrino mass? A host of international experiments to look for neutrinoless double beta decay may shed light on these questions. “They are all fantastic projects, and they use different technologies,” says the University of North Carolina’s John Wilkerson, project director of an experiment called Majorana.
Beta decay, in which a neutron turns into a proton by ejecting an electron and an antineutrino, is common. In double beta decay, two neutrons in a single nucleus each eject an electron. The process has been observed with the emission of two antineutrinos. But more scientifically interesting is neutrinoless double beta decay, which would require the antineutrinos to effectively annihilate each other, indicating that they are Majorana particles, that is, their own antiparticle. To date, just one unconfirmed sighting has been reported. Says Wilkerson, “I think the groups completely agree that to...
