A small CeCl3 crystal (6.9 g) was measured deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of the INFN (Italy) with a low background HP Ge detector (244 cm3) during 1280 h. The crystal is not polluted by 232Th, 40K, 60Co, 137Cs (limits were set on the activity at a level of 0.05-1 Bq/kg), but contains radioactive 138La (0.68 Bq/kg) and, probably, is polluted by 235U and 238U (0.3-0.7 Bq/kg). The half life limits for different double β processes in 136Ce and in 138Ce were set in the range of (1-6)×10 yr. In particular, the 2&z.epsiv; captures in 136Ce to various excited levels of 136Ba were considered for the first time. The limits for the resonant neutrinoless transitions to the 2392.1 keV and 2399.9 keV levels of 136Ba are: T>2.4×10 yr and T>4.1×10 yr at 90% C.L., respectively.
Belli, P., Bernabei, R., D'Angelo, S., Cappella, F., Cerulli, R., Incicchitti, A., et al. (2009). First limits on neutrinoless resonant 2EC in 136Ce and new limits for other 2beta processes in 136Ce and 138Ce isotopes. NUCLEAR PHYSICS. A, 824, 101-114 [10.1016/j.nuclphysa.2009.03.012].
First limits on neutrinoless resonant 2EC in 136Ce and new limits for other 2beta processes in 136Ce and 138Ce isotopes
BERNABEI, RITA;D'ANGELO, SILIO;
2009-01-01
Abstract
A small CeCl3 crystal (6.9 g) was measured deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of the INFN (Italy) with a low background HP Ge detector (244 cm3) during 1280 h. The crystal is not polluted by 232Th, 40K, 60Co, 137Cs (limits were set on the activity at a level of 0.05-1 Bq/kg), but contains radioactive 138La (0.68 Bq/kg) and, probably, is polluted by 235U and 238U (0.3-0.7 Bq/kg). The half life limits for different double β processes in 136Ce and in 138Ce were set in the range of (1-6)×10 yr. In particular, the 2&z.epsiv; captures in 136Ce to various excited levels of 136Ba were considered for the first time. The limits for the resonant neutrinoless transitions to the 2392.1 keV and 2399.9 keV levels of 136Ba are: T>2.4×10 yr and T>4.1×10 yr at 90% C.L., respectively.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
