What is the reason for the beta decay?

Beta decay puzzle solved

During beta decay, either a neutron in an atomic nucleus is converted into a proton, releasing an electron and an antineutrino. Or a proton decays into a neutron, releasing a positron and a neutrino. Nuclear physicists have been puzzled for around half a century. Because the measured decay rate of atomic nuclei is lower than expected. In the specialist journal “Nature Physics”, scientists now report why this could be: Under the extreme conditions inside atomic nuclei, the interactions between several protons and neutrons play a greater role than assumed.

So far, physicists have used a computer trick to explain the measured decay rate: They multiplied the theoretical value by a correction factor so that the results matched the experimental values ​​again. Peter Gysbers from the University of British Columbia in Vancouver and his colleagues have now used a supercomputer to determine where this factor comes from and how it can be determined more precisely. The team simulated the beta decay of light and medium-weight elements up to tin-100. The complicated calculations showed that interactions that had not yet been taken into account also play a role in beta decay. According to this, two protons can decay into one proton and one neutron, or one proton and one neutron can become two neutrons.

The new study opens up a deeper insight into atomic nuclei. Understanding beta decay as precisely as possible is important, for example, for experiments that use so-called exotic beta decays to search for deviations from the standard model of particle physics. In particular, the so-called neutrino-free double beta decay would indicate novel interactions. The theoretical predictions of this decay, however, vary greatly, depending on which theoretical model the scientists use. Thanks to the calculation method that has now been developed, future calculations should be much more precise.