Search for the double-beta decay of 82Se to the excited states of 82Kr with NEMO-3

2020

The double-beta decay of 82Se to the 0+1 excited state of 82Kr has been studied with the NEMO-3 detector using 0.93 kg of enriched 82Se measured for 4.75 y, corresponding to an exposure of 4.42 kg y. A dedicated analysis to reconstruct the gamma-rays has been performed to search for events in the 2e2g channel. No evidence of a 2nbb decay to the 0+1 state has been observed and a limit of T2n 1/2(82Se; 0+gs -> 0+1) > 1.3 1021 y at 90% CL has been set. Concerning the 0nbb decay to the 0+1 state, a limit for this decay has been obtained with T0n 1/2(82Se; 0+g s -> 0+1) > 2.3 1022 y at 90% CL, independently from the 2nbb decay process. These results are obtained for the first time with a tracko-…

Search for Neutrinoless Quadruple-β Decay of 150Nd with the NEMO-3 Detector

2017

We report the results of a first experimental search for lepton number violation by four units in the neutrinoless quadruple-β decay of 150Nd using a total exposure of 0.19 kg yr recorded with the NEMO-3 detector at the Modane Underground Laboratory. We find no evidence of this decay and set lower limits on the half-life in the range T1/2>(1.1–3.2)×10^21  yr at the 90% C.L., depending on the model used for the kinematic distributions of the emitted electrons. peerReviewed

Measurement of the 2νββ decay half-life of 150Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector

2016

We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope 150Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a complete background model for this isotope, including a measurement of the two-neutrino double-β decay half-life of T2ν 1=2 ¼ ½9.34 0.22ðstatÞ þ0.62 −0.60 ðsystÞ × 1018 y for the ground state transition, which represents the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay mechanisms. As no evidence for 0νββ decay is observ…

Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of Ca48 with the NEMO-3 detector

2016

The NEMO-3 experiment at the Modane Underground Laboratory investigates the double-beta decay of Ca48. Using 5.25 yr of data recorded with a 6.99 g sample of Ca48, approximately 150 double-beta decay candidate events are selected with a signal-to-background ratio greater than 3. The half-life for the two-neutrino double-beta decay of Ca48 is measured to be T2ν1/2=[6.4+0.7−0.6(stat)+1.2−0.9(syst)]×1019  yr. A search for neutrinoless double-beta decay of Ca48 yields a null result, and a corresponding lower limit on the half-life is found to be T0ν1/2>2.0×1022  yr at 90% confidence level, translating into an upper limit on the effective Majorana neutrino mass of ⟨mββ⟩<6.0–26  eV, with the rang…

Detailed studies of 100 Mo two-neutrino double beta decay in NEMO-3

2019

Measurement of the 2νββ decay half-life and search for the 0νββ decay of 116Cd with the NEMO-3 detector

2017

The NEMO-3 experiment measured the half-life of the 2νββ decay and searched for the 0νββ decay of 116Cd. Using 410 g of 116Cd installed in the detector with an exposure of 5.26 y, (4968±74) events corresponding to the 2νββ decay of 116Cd to the ground state of 116Sn have been observed with a signal to background ratio of about 12. The half-life of the 2νββ decay has been measured to be T2ν1/2=[2.74±0.04(stat)±0.18(syst)]×1019  y. No events have been observed above the expected background while searching for 0νββ decay. The corresponding limit on the half-life is determined to be T0ν1/2≥1.0×1023  y at the 90% C.L. which corresponds to an upper limit on the effective Majorana neutrino mass of…

Final results on 82Se double beta decay to the ground state of 82Kr from the NEMO-3 experiment

2018

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (2νββ) half-life of 82Se as T2ν1/2=[9.39±0.17( stat )±0.58( syst )]×1019 y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is ∣∣M2ν∣∣=0.0498±0.0016. In addition, a search for neutrinoless double beta decay (0νββ) using 0.93 kg of 82Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of T0ν1/2>2.5×1023 y (90% C.L. ) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of ⟨mν⟩<(1.2−3.0) eV , where the range reflec…