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

Abstract

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 (ββ_ov) is also possib1e, and in this case the two ejected electrons carry all the energy released in the process.