Search for double β decays of 96Ru and 104Ru
The spectrum with the sample was accumulated over 158 h, while background data were taken over 1046 h. Radioactive contamination of the ruthenium sample has been estimated.
We have investigated various double beta decay modes of 96Ru and also of the 2β- decaying 104Ru isotope. No evidence for the presence of the decay processes searched for has been obtained and new half life limits were set.
In the table the studied decay modes and the correspondent obtained upper limits are summarized.
In particular, new limits on 2β processes in 96Ru in the range of 1018-19 yr have been obtained; they are two or three orders of magnitude higher than the previously available ones. The search for 2β transition of 104Ru to the 556 keV excited level of 104Pd was carried out at the first time.
The experiment is in progress. Its sensitivity is limited mainly by contamination of the ruthenium by potassium. R&D to purify the material is under way. Moreover, another Ruthenium sample of about 500 g mass is also in measurement.