Neutrinoless double beta decay: current results and future outlook

Neutrinos were first proposed in 1930 as a “desperate remedy” to save the conservation of energy and angular momentum, but there were doubts that this particle could ever be detected. Almost a century later, not only have we detected all three flavors of the neutrino but have also observed neutrinos exhibit behavior that cannot be explained by the standard model of particle physics, raising fundamental open questions. One such important open question is whether the neutrino is a Majorana fermion, i.e., whether it is its own antiparticle. The observation of Neutrinoless Double Beta Decay (0νββ) — which is a hypothesized, beyond Standard Model process — would conclusively establish the Majorana nature of neutrinos. It would also demonstrate lepton number violation and could provide insight into the absolute neutrino mass scale.

These experiments are extremely challenging, especially due to stringent background reduction requirements. Previous experimental searches for 0νββ now exclude the half-life up to O(10²⁶ yr). The next generation tonne-scale experiments aim to have a sensitivity to a decay half-life beyond O(10²⁸ yr). In this talk, I will give an overview of the major technologies and experiments in the field. I will summarize the present results and discuss the efforts underway for the next generation experiments.