Monte Carlo Simulation of a Double-Beta Decay Experiment with Superconducting-Superheated Tin Granules

The double beta process[1] is a rare but very important nuclear decay mode which exists in some tens of even-A nuclei, where the relative position of the energy states of the isobars is abnormal, i.e. the usual β decay (A,Z) → (A, Z ± 1) is energetically forbidden -or very hindered because of selection rules-, leaving the ββ transition (A,Z) → (A, Z ± 2) as the only allowed way of decaying. In the nuclear tables one rrlay find up to 26 cases of β−β− parents [2]. Their decay, if the neutrino is a Dirac particle \((v \ne \bar v)\), leads to the daughter nuclei plus two electrons and two antineutrinos in the so called two-neutrino double beta decay (β−β− 2v). If the neutrino is a Majorana fermion \((v = \bar v)\) and hence the lepton number L is not conserved, then in addition to that mode the neutrinoless one (ββov) is also possib1e, and in this case the two ejected electrons carry all the energy released in the process.