First results of the experiment to search for 2β decay of 106Cd with 106CdWO4 crystal scintillator in coincidence with four crystals HPGe detector

Cadmium tungstate crystal scintillators enriched in 116Cd to 82% (116CdWO4, total mass of ≈1.2kg) are used to search for 2β decay of 116Cd deep underground at the Gran Sasso National Laboratory of the INFN (Italy). The radioactive contamination of the116CdWO4 crystals has been studied carefully to reconstruct the background of the detector. The measured half-life of 116Cd relatively to 2ν2β decay is T1/22ν2β = [2.8 ± 0.05(stat.) ± 0.4(syst.)] × 1019 yr, in agreement with the results of previous experiments. The obtained limit on the 0ν2β decay of 116Cd (considering the data of the last 8696 h run with an advanced background 0.12(2) counts/yr/kg/keV in the energy interval 2.7−2.9 MeV) is T1/2 ≥ 1.0 × 1023 yr at 90% C.L. The sensitivity of the experiment to the 0ν2β process is lim T1/2 = 3 × 1023 yr at 90% C.L. over 5 years of the measurements and it can be advanced (by further reduction of the background by a factor 3−30) to the level of lim T1/2 = (0.5-1.5) × 1024 yr for the same period of the data taking.