A search for various double beta decay modes of tin isotopes

For the first time an extensive search for various double beta decay modes of 124Sn and 112Sn has been performed. A total exposure of 43.29 kg days has been accumulated. New half-life limits of 124Sn into excited states of 124Te have been obtained; the lower half-life limit for the first excited 2+ state at 602.7 keV is T1/2>3.1×1018 yr (90% CL) and for the first excited 0+ state T1/2>7.7×1018 yr (90% CL). For the very first time, ground state and excited state transitions of 112Sn have been experimentally explored. The obtained half-life limits for EC/EC and β+/EC into the first excited 2+ state of 112Cd are both T1/2>1.4×1018 yr (90% CL). A resonance enhancement in the decay rate for 0ν EC/EC might be expected for the 0+-state at 1870.9 keV due to degeneracy with the 112Sn ground state. No signal was found resulting in a lower half-life limit of T1/2>1.6×1018 yr (90% CL) for this decay. As all the excited state searches are based on gamma-lines, all half-life limits apply for both neutrino and neutrino-less modes. Neutrinoless ground state transitions were searched for in the EC/EC and β+/EC mode and a limit of T1/2>1.5×1018 yr (90% CL) was obtained for EC/EC decays of 112Sn, whilst the β+/EC mode results are inconclusive.