Search for 2β decay of ¹¹⁶Cd with the help of enriched ¹¹⁶CdWO₄ crystal scintillators

¹ Institute for Nuclear Research, MSP 03680 Kyiv, Ukraine
² Institute of Theoretical and Experimental Physics, 117259 Moscow, Russia
³ Dipartimento di Fisica, Università di Roma “Tor Vergata”, I-00133 Rome, Italy
⁴ INFN, sezione di Roma "Tor Vergata" , I-00133 Rome, Italy
⁵ Dipartimento di Fisica, Università di Roma “La Sapienza”, I-00185 Rome, Italy
⁶ INFN, sezione di Roma "La Sapienza" I-00185 Rome, Italy
⁷ Laboratori Nazionali del Gran Sasso, INFN, I-67100 Assergi (AQ), Italy
⁸ Nikolaev Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia

^a e-mail: poda@kinr.kiev.ua

Published online: 10 January 2014

Abstract

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 T_1/2^2ν2β = [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 T_1/2 ≥ 1.0 × 10²³ yr at 90% C.L. The sensitivity of the experiment to the 0ν2β process is lim T_1/2 = 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 T_1/2 = (0.5-1.5) × 10²⁴ yr for the same period of the data taking.