Results of a search for 2β-decay of Xe-136 with high pressure copper proportional counters in Baksan Neutrino Observatory INR RAS

Search for \beta \beta -decay of Xe-136 with two high pressure proportional counters is carried out in Baksan Neutrino Observatory. The experiment is based on comparision of spectra measured with natural and enriched xenon. The measured halfe life is equal to T_{1/2}=5.5^{+4.6}_{-1.7} \cdot 10^{21} yr (67% C.L.) for \beta \beta 2\nu -decay mode. No evidence has been found for neutrinoless \beta \beta -decay. The decay half life limit based on data measured during 17280 h is T_{1/2}(\beta\beta 0\nu)\geq 4.9 \cdot 10^{23} yr (90% C.L.).