Search for double beta processes in 106Cd with enriched 106CdWO4 crystal scintillator in coincidence with four crystals HPGe detector

A radiopure cadmium tungstate crystal scintillator, enriched in 106Cd (106CdWO4), was used to search for double beta decay processes in 106Cd in coincidence with an ultra-low background set-up containing four high purity germanium (HPGe) detectors in a single cryostat. The experiment has been completed after 13085 h of data taking. New improved limits on most of the double beta processes in 106Cd have been set on the level of 1020−1021 yr. Tn particular, the half-life limit on the two neutrino electron capture with positron emission, T1/2 ≥ 1.8 × 1021 yr, reached the region of theoretical predictions.