Measurement of double beta decay of 100Mo to excited states in the NEMO 3 experiment

Abstract

23 pages, 7 figures, 4 tables, submitted to Nucl. PhysThe double beta decay of 100Mo to the 0+1 and 2+1 excited states of 100Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of 100Mo to the excited 0+1 state is measured to be T(2nu)_1/2 = [5.{+1.3-0.9}(stat)+/-0.8(syst)]x 10 20 y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0+_1 state has been found. The corresponding half-life limit is T^(0nu)_1/2(0+ --> 0+_1) > 8.9 x 10 22 y (at 90% C.L.). The search for the double beta decay to the 2+_1 excited state has allowed the determination of limits on the half-life for the two neutrino mode T(2nu)_1/2(0+ --> 2 +_1) > 1.1 x 10 21 y (at 90% C.L.) and for the neutrinoless mode T(0nu)_1/2(0 + --> 2+_1) > 1.6 x 10 23 y (at 90% C.L.)

Statistics of neutrinos and the double beta decay

“…The best lower bound on the 2νββ-decay half-life to excited 2 + 1 state is 1.6 10 21 years [20]. The current limit of NEMO-3 experiment is 1.1 10 21 years [21] (for 1 year of measurements). After 5 years of measurements with the present low-radon background conditions sensitivity will increase up to ∼ 10 22 years thus approaching the prediction in the case of bosonic neutrinos.…”

Experimental study of Tc100 β decay with total absorption γ -ray spectroscopy

“…1 ( 100 Mo, 100 Tc, 100 Ru) [8][9][10][11][12]. Double β-decay rates to the ground state and to the first-excited 0 + state of 100 Ru [13] have been measured in the NEMO 3 experiment [14]. The EC branch of the decay 100 Tc → 100 Mo has been measured recently with much higher precision than before [15].…”

Measurement of theββDecay Half-Life ofTe130with the NEMO-3 Detector

“…This uncertainty is determined with a calibrated 207 Bi source and a dedicated 90 Sr source which decays to 90 Y, a pure β emitter of Q β = 2.28 MeV. Finally, the source foil thickness and the geant model of electron energy losses in dense thin media contribute a systematic uncertainty of 4% which is estimated by comparing signals from metallic and composite 100 Mo source foils [15]. The total systematic uncertainty of 15% is obtained by adding the individual contributions in quadrature.…”