Main results from four enriched large modules (ZMO and LMO stand for ZnMoO4 and Li2MoO4, respectively; t and b stand for top and bottom, with reference to the sample position in the crystal boule). DP designates the discrimination power as defined in. All the DP values imply a rejection power > 99:9% with a selection effciency > 90%.
|
Enriched sample |
Mass [g] |
FWHM @ 2615 keV |
Light Yield [keV/MeV] |
α/β rejection |
A(228Th) [μBq/kg] |
A(226Ra) [μBq/kg] |
A(210Po) [μBq/kg] |
|
ZMO-t |
380 |
9 keV |
1.3 |
DP=7.8 |
< 8 |
14 |
0.8 |
|
ZMO-b |
382 |
18 keV |
1.2 |
DP=11 |
< 21 |
23 |
2.4 |
|
LMO-t |
186 |
7 keV |
- |
DP=17 |
< 6 |
<6 |
0.21 |
|
LMO-b |
204 |
5 keV |
0.8 |
DP=12 |
< 6 |
<11 |
0.06 |
The excellent performance of the enriched Li2MoO4 detectors can be appreciated in Fig. 1. From the background measurement, it is possible to extract preliminarily the half-life of the ordinary two-neutrino double-beta decay, with a very simple background model which includes only the internal 40K contamination and describes the continuum of the residual background with an exponential function decreasing with energy. The results are 7.5 1018 y and 6.7 1018 y for the LSM and LNGS data respectively, in good agreement with the accurate NEMO-3 and LUCIFER measurements.
