Neutrinos

A hypothetical nuclear process known as neutrinoless double beta decay ought to be among the least likely events in the universe. Now the international EXO-200 collaboration, which includes researchers from the Department of Energy’s SLAC National Accelerator Laboratory, has determined just how unlikely it is: In a given volume of a certain xenon isotope, it would take more than 35 trillion trillion years for half of its nuclei to decay through this process – an eternity compared to the age of the universe, which is “only” 13 billion years old.