How heavy is a neutrino?

Illustration by Sandbox Studio, Chicago with Corinne Mucha

The full article appears in Symmetry. It contains some great ideas for explaining neutrinos to your friends and family!

Over the years, scientists have learned several surprising things about (neutrinos). But they have yet to answer what might sound like a basic question: How much do neutrinos weigh?

We know that the masses of the first two neutrinos are close together and that the third is the odd one out. What we don’t know is whether the third one is lighter or heavier than the others…

The question of whether this third mass state is the heaviest or the lightest mass state is called the neutrino mass hierarchy (or neutrino mass ordering) problem…

It will take years of data collection to get the first hint of an answer. (Long-baseline neutrino experiments NOvA and T2K are taking related measurements.) The JUNO experiment under construction in China aims to measure the mass hierarchy in a different way. The definitive measurement likely won’t come until the next generation of long-baseline experiments, DUNE in the US and the proposed Hyper-Kamiokande experiment in Japan…

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