The Aurora experiment at the underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (INFN, Italy) investigated double beta decay of 116Cd with the help of 1.16-kg cadmium tungstate crystal scintillators enriched in 116Cd to 82% (116CdWO4). The half-life of 116Cd relative to the 2ν2β decay to the ground state of 116Sn was measured with the highest up-to-date accuracy as T1/2 = 2.63 +0.11–0.12 × 1019 yr. A new limit on the 0ν2β decay of 116Cd to the ground state of 116Sn was set as T1/2 ≥ 2.2 × 1023 yr at 90% C.L., which is the most stringent known restriction for this isotope. The data collected with highly radiopure 116CdWO4 crystal scintillators during 26831 h was decided to be also used for a search of long-lived superheavy ekatungsten at the high energy part of the measured α spectrum. The limit obtained in these measurements is in agreement with those obtained in recent experiments which instead look for spontaneous fission of superheavy elements or use the accelerator mass spectrometry.
Oksana G. Polischuk
Institute for Nuclear Research