New limits on double beta processes in 106-Cd

TL;DR

This study used a highly sensitive cadmium tungstate scintillator and ultra-low background detectors to set new, more stringent limits on double beta decay processes in 106-Cd, reaching levels close to theoretical predictions.

Contribution

The paper presents the first application of a radiopure 106-Cd-enriched crystal with ultra-low background detectors to improve limits on double beta decay in 106-Cd.

Findings

Half-life limits on double beta processes in 106-Cd are now at 1e20-1e21 years.

The limit on two-neutrino electron capture with positron emission is T1/2 > 1.1e21 years.

Resonant neutrinoless double electron captures are restricted to T1/2 > 8.5e20 - 1.4e21 years.

Abstract

A radiopure cadmium tungstate crystal scintillator, enriched in 106-Cd to 66%, with mass of 216 g (106-CdWO4) was used in coincidence with four ultra-low background HPGe detectors contained in a single cryostat to search for double beta decay processes in 106-Cd. New improved half-life limits on the double beta processes in 106-Cd have been set on the level of 1e20-1e21 yr after 13085 h of data taking deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN (Italy). In particular, the limit on the two neutrino electron capture with positron emission T1/2 >1.1e21 yr, has reached the region of theoretical predictions. The resonant neutrinoless double electron captures to the 2718, 2741 and 2748 keV excited states of 106-Pd are restricted on the level of T1/2 > 8.5e20 - 1.4e21 yr.