Vd. Ashitkov et al., STUDY OF DOUBLE-BETA DECAY OF 100MO WITH LIQUID-ARGON IONIZATION-CHAMBER (FIRST RESULTS), Physics of atomic nuclei, 61(6), 1998, pp. 910-914
The experiment being discussed is located at the Gran Sasso Undergroun
d Laboratory (3500 mwe). The full weight of Mo-100 under investigation
is 138.7 g. The first measurement run was performed (measurement time
202 h). As a result, limits on half-lives for the 0 nu and 0 nu chi(0
) decays of Mo-100 were obtained at a 90% C. L. (greater than 0.8 x 10
(21) yr and 0.8 x 10(20) yr, respectively). Some extra events in the e
nergy region 1.6-2.6 MeV lead, in the conservative approach, only to t
he limit of greater than 0.5 x 10(19) yr (at a 90% C. L.) on the 2 nu
beta beta decay of Mo-100. As a by-product, the limit on the content o
f radioactive Ar-42 natural Ar was obtained to be less than 5 x 10(-21
) g/g. We plan to improve the background conditions of the experiment
and to increase the sensitivity to (1-5) x 10(23) yr for the 0 nu deca
y mode and to (2-5) x 10(22) yr for the 0 nu chi(0) decay mode in one
year of measurement. In addition, we hope to investigate the 2 nu deca
y mode for Mo-100 to a high precision.