Double-Beta decay (2νββ) is a second order electro-weak process and, thus, much rarer than the well known single-beta decay. Single-beta decay is not energetically allowed in certain even-even nuclei; however, in such nuclei 2νββ can be observed. Two beta decays occur simultaneously, resulting in the emission of two electrons and two electron anti-neutrinos. It took 52 years from when Maria Goeppert-Mayer first postulated 2νββ in 1935, until it was first observed in ⁸²Se. This process has now been observed in various naturally existing isotopes with half–lives above 10¹⁸ years. The observation of even rarer decays is now within grasp with advances in low background measurement techniques. If neutrinos are Majorana particles, an even rarer event – neutrinoless double-beta decay (0νββ) – can occur.

As opposed to 2νββ, no anti-neutrinos would be emitted, thus violating lepton number conservation. Therefore, the two electrons carry away all the energy of the decay, producing a peak at the end of the broad 2νββ summed electron energy spectrum. This mono-energetic peak is the key experimental signature of 0νββ. The anti-neutrinos are exchanged as a virtual particle in the nucleus, via light Majorana neutrino exchange. More exotic mechanisms for 0νββ have been proposed; nevertheless, regardless of the mechanism, the observation of such a phenomenon would imply that neutrinos are Majorana particles, and as such, they constitute their own antiparticles.

My work on 0νββ encompasses a multidisciplinary approach involving software, electronics, and hardware. As a member of the MAJORANA and LEGEND collaborations, my research advances the search for 0νββ in ⁷⁶Ge using High Purity Germanium (HPGe) detectors. ⁷⁶Ge has long been at the forefront of the search for 0νββ. The technology has set some of the best limits on half-life of 0νββ to date as demonstrated by the MAJORANA DEMONSTRATOR and the Germanium Detector Array (GERDA). Ge detectors have long been a standard in the field of nuclear and particle physics and are very well posed for this search.

The Large Enriched Germanium Experiment for Neutrinoless Double-Beta Decay (0νββ) (LEGEND) will combine the best techniques from the MAJORANA DEMONSTRATOR and GERDA to search for 0νββ in ⁷⁶Ge. The LEGEND collaboration is pursuing a phased approach to a ton-scale ⁷⁶Ge experiment, with ultimate discovery potential at a half–life beyond 10²⁸ years. The first phase, LEGEND-200, is the deployment of 200 kg of enriched ⁷⁶Ge detectors in the GERDA cryostat at the LNGS underground laboratory in Italy.