Search for double-βdecays of tin isotopes with enhanced sensitivity

Abstract

A search for the various double beta decay modes of 124 Sn and 112 Sn has been performed on 75 kg•days of data. New half-life limits for excited states in 124 Sn have been obtained including a lower limit for decay into the first excited 2 + state of 124 Te of T 1/2 > 0.87 × 10 20 yrs (90%CL) and into the first excited 0 + state of T 1/2 > 1.08 × 10 20 yrs (90%CL). Ground state and excited state transitions of 112 Sn have also been experimentally explored. A limit for the 2νEC/EC of T 1/2 > 1.8 × 10 19 yrs (90%CL) is obtained. The non-observation of de-excitation gammas from the 0 + at 1888.5 keV results in a lower half-life limit on the 0νEC/EC decay of 112 Sn of T 1/2 > 0.8 × 10 19 yrs (90%CL), despite a possible resonant enhancement of the decay rate due to degenerated states.

Shell model predictions forSn124double-βdecay

“…First, because it was not included in the finetuning, and in addition, the experimental data available is not very clear about the first excited 0 + state, which is very important for our analysis. In particular, although the recent double-beta decay experimental studies [28][29][30] assume that this state is at 1.156 MeV excitation energy, the latest Nuclear Data Sheets [71,72] Fig. 1).…”

“…As we mentioned in the Introduction, double-beta decay modes of 124 Sn were recently investigated experimentally by several groups [28][29][30][31]. The emphasis was on decays to the excited states, but no signal has been seen so far.…”

“…As a consequence, the phase space factor (see below) for 2νββ decay of 124 Sn is about ten times larger than that of 76 Ge, while the 0νββ phase space factor of 124 Sn is about four times larger than that of 76 Ge. Double-beta decay modes of 124 Sn were also recently investigated experimentally by several groups [28][29][30][31], but no signal has been seen so far. The best upper limit obtained was about 1×10…”

Shallow-underground accelerator sites for nuclear astrophysics: Is the background low enough?

“…Recently a new ultra-low background germanium detector made of specially selected components went into operation [27]. In recent years, also nuclear astrophysics [30] and rare nuclear decay [31] studies have been performed at Felsenkeller. Tunnels I-III and V-IX are used as storage sites by local businesses.…”

Degeneracy at 1871 keV inCd112and implications for neutrinoless double electron capture

“…The precise energies of the doublet of levels at 1871 keV, for which the 0 + member has been suggested as a possible daughter state following neutrinoless double electron capture of 112 Sn, were determined to be 1871.137(72) keV (0 One of the most pressing issues in subatomic physics today is the question of the nature of the neutrino. The observation of neutrino oscillations [1][2][3] has revealed neutrino mixing and that neutrinos are massive particles or, more precisely, that at least two of the mass eigenstates are nonzero. However, it is still unknown if neutrinos are their own antiparticles (Majorana) or distinct from their antiparticles (Dirac).…”