Neutrinos are ubiquitous elementary particles that interact only very weakly with normal matter. Therefore, they usually penetrate it unhindered and are therefore also called ghost particles. Nevertheless, neutrinos play a predominant role in the early universe. In order to fully explain how our universe evolved, we need above all to know their mass. But so far, it has not been possible to determine this mass.
The international Project 8 collaboration wants to change this with its new experiment. For the first time, Project 8 is using a completely new technology to determine the neutrino mass, the so-called “Cyclotron Radiation Emission Spectroscopy” — CRES for short. In a recent publication in the journal Physical Review Letters, the Project 8 collaboration has now been able to show that the CRES method is indeed suitable for determining the neutrino mass and has already set an upper limit for this fundamental quantity in a first measurement — an important milestone has thus been reached. From Johannes Gutenberg University Mainz (JGU), the research groups of Prof. Dr. Martin Fertl and Prof. Dr. Sebastian Böser are involved, both researchers at the Cluster of Excellence PRISMA+. Dr. Christine Claessens, former PhD student of Sebastian Böser and now postdoc at the University of Washington in Seattle (USA), made a crucial contribution to the current publication as part of her PhD thesis.
Electrons as the key to neutrino mass
The Project 8 experiment uses the beta decay of radioactive tritium to track neutrino mass. Tritium is a heavy relative of hydrogen — a so-called isotope. It is unstable and consists of one proton and two neutrons. By converting one of these neutrons into a proton, tritium decays to helium while emitting an electron and an antineutrino. “And here’s the kicker,” says Martin Fertl. “Since neutrinos and their antiparticles have no electric charge, they are very difficult to detect. Therefore, we don’t even try to detect them. Instead, we…