摘要
We report the first results on 76Ge neutrinoless double beta decay from stage one of the China dark-matter experiment （CDEX）. A p-type point-contact high-purity germanium detector with a mass of 994g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304kgd has been analyzed over a wide spectral band from 500keV to 3MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039MeV energy range. The half-life of76Ge neutrinoless double beta decay derived based on this result is 70v2〉6.4× 1022 yr （90%C.L.）. An upper limit on the effective Majorana-neutrino mass of 5.0eV has been achieved.
We report the first results on ^(76)Ge neutrinoless double beta decay from stage one of the China dark-matter experiment(CDEX).A p-type point-contact high-purity germanium detector with a mass of 994 g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg d has been analyzed over a wide spectral band from 500 keV to 3 MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039 MeV energy range. The half-life of ^(76)Ge neutrinoless double beta decay derived based on this result is T^(0ν)1/2>6.4×10^(22) yr(90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved.
基金
supported by the National Natural Science Foundation of China(Grant Nos.11275107,11475117,11475099,and 11675088)
the National Key Basic Research Program of China(Grant No.2010CB833006)
