How charmonium particles melt as the universe heats up

Charm quarks bound together into charmonium states don't survive intact at high temperatures; instead they acquire thermal width—a measure of how quickly they decay. Using lattice QCD simulations, researchers found all charmonium states survive up to 305 MeV but become increasingly blurred and short-lived as temperature rises. Smaller particles decay slower than larger ones, a hierarchy that helps physicists understand how matter behaves in the extreme conditions of the early universe and particle accelerators.