Astroparticle physicists observe the longest half-life ever directly measured

The universe is almost 14 billion years old. An inconceivable length of time by human standards - yet compared to some physical processes, it is but a moment. There are radioactive nuclei that decay on much longer time scales. An international team of scientists has now directly measured the rarest decay process ever recorded in a detector. Using the XENON1T detector which mainly searches for dark matter at the INFN Gran Sasso National Laboratory, the researchers were able to observe the decay of Xenon-124 atomic nuclei for the first time. The half-life of a process is the time after which half of the radioactive nuclei present in a sample have decayed away. "The half-life measured for Xenon-124 is about one trillion times longer than the age of the universe," says Dr. Alexander Fieguth, who carried out a major part of the experimental analyses as part of his PhD thesis at the University of Münster - for which he received a University Dissertation Prize.