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New Faculty Profile: Professor Ryan MacLellan

Ryan MacLellan joined the University of Kentucky as an assistant professor of physics in early 2020. Ryan was an assistant professor at the University of South Dakota for the five years prior.

Originally from Nova Scotia, Canada, Ryan received his Ph.D. on the energy calibration of the SNO experiment in 2009 from the Queen’s University. He went on to do a postdoc at the University of Alabama and then was a research associate at SLAC National Accelerator Laboratory before moving to the University of South Dakota in 2014. The discovery of neutrino mass by the SNO experiment, earned his Ph.D. supervisor Art McDonald a share of the 2015 Nobel Prize in Physics; and Ryan, along with the rest of the SNO Collaboration, a share in the 2016 Breakthrough Prize in Fundamental Physics.

His primary research interests remain with neutrinos. Now that it is known that neutrinos have mass, the past and future experiments on which Ryan collaborates, EXO-200 and nEXO, seek to determine what that small mass is, but, more fundamentally, whether neutrinos are their own antiparticles. This discovery would help to explain why the Universe is made up of matter and not roughly equal parts matter and antimatter, as one would expect.

Since neutrinos are so difficult to detect, producing some, tracking them, and observing them some time later as their antiparticle, is effectively impossible. Only through the process of neutrinoless double-beta decay, where the source and detector of these neutrinos are within the same nucleus (very close together) and through the magnitude of Avogadro’s number (for kilogram quantities of these nuclei) is there hope to observe the nature of the neutrino. The nEXO project is one of two ton-scale experiments proposed to extend current and past searches for this decay. Both are in the research and development phase as the projects progress through the Department of Energy’s Critical Decision approvals process.