Physical Society Colloquium

Discovering the Origin of Matter with LEGEND

Julieta Gruszko

Department of Physics and Astronomy
University of North  Carolina at Chapel Hill

Why is the universe dominated by matter, and not antimatter? Neutrinos, with their changing flavors and tiny masses, could provide an answer. If the neutrino is a Majorana particle, meaning that it is its own antiparticle, it would reveal the origin of the neutrino's mass, demonstrate that lepton number is not a conserved symmetry of nature, and provide a path to leptogenesis in the early universe. To discover whether this is the case, we must search for neutrinoless double-beta decay, a theorized process that would occur in some nuclei. By searching for this extremely rare decay, we can explore new physics at energy scales that only existed in the seconds following the Big Bang.

Detecting this extremely rare process, however, requires us to build very large detectors with very low background rates. The LEGEND experiment, which searches for the neutrinoless double-beta decay of ⁷⁶Ge, builds on the success of GERDA and the Majorana Demonstrator, which have achieved the lowest background levels and the best energy resolution in the region-of- interest in the field. I'll discuss LEGEND-200's first results and LEGEND-1000's projected discovery potential.