The search for neutrino-less double-beta decay

Abstract

The search for neutrino-less double-beta decay has been a very active field of research in the last decade. Neutrino-less double-beta decay may answer essential open questions in neutrino physics. While double-beta decay accompanied by the emission of two neutrinos is allowed by the Standard Model, the neutrino-less process requires neutrinos to be Majorana particles. Detecting this decay could determine the nature of neutrinos, the neutrino effective mass, and the mass hierarchy. Xenon-136 and germanium-76 experiments currently have the best sensitivities. For both isotopes the lifetime of neutrino-less double-beta decay has been determined to be longer than 1025 years, several orders of magnitude slower than the slowest process that has been detected. In this paper the basic theory of neutrino-less double-beta decay and its relationship to the neutrino mass are discussed. A review of the experimental efforts underway to measure this decay is presented, along with the status and sensitivity of current and near future searches.