Results of the NEMO3 experiment

TL;DR

The NEMO3 experiment searched for neutrinoless double beta decay in isotopes of molybdenum and selenium, setting new limits on decay half-lives and neutrino masses, and analyzing decay to excited states of ruthenium.

Contribution

This paper reports the first limits on neutrinoless double beta decay for these isotopes and detailed analysis of decay to excited states, advancing understanding of neutrino properties.

Findings

Half-life limits for neutrinoless double beta decay: Mo > 4.6×10^{23} years, Se > 1.0×10^{23} years.

Constraints on neutrino effective mass: <m_ν> < 0.7-2.8 eV (Mo), > 1.7-4.9 eV (Se).

Measured two-neutrino double beta decay half-life for Mo: approximately 5.7×10^{20} years.

Abstract

The purpose of the NEMO3 experiment is to detect neutrinoless double beta decay in order to determine the nature of neutrino and its absolute mass. We analysed the 389 effective days of data from the $\sim 7$ kg of $^{100}$Mo and $\sim 1$ kg of $^{82}$Se and obtained the following limits on the half-life for the \bb process: $T_{1/2}(\beta\beta0 \nu) > 4.6 \times 10^{23}$ years (Mo) and $T_{1/2}(\beta \beta 0 \nu) > 1.0 \times 10^{23}$ years (Se). The corresponding limits on the neutrino effective mass are $<m_{\nu}> <$ 0.7 - 2.8 eV (Mo) and $<m_{\nu}> >$ 1.7 - 4.9 eV (Se) at 90% Confident Level. We also performed a detailled analysis on the double beta decay of $^{100}$Mo into the excited states $0^+_1$, $2^+_1$ of $^{100}$Ru. The results are: $T_{1/2}(\beta \beta 2 \nu \to 0^+_1) = 5.7^{+1.3}_{-0.9}(stat)\pm 0.7 (syst) \times 10^{20}$ years, $T_{1/2}(\beta \beta 2 \nu \to 2^+_1) > 1.1 \times 10^{21}$ years, $T_{1/2}(\beta \beta 0 \nu \to 0^+_1) > 8.9 \times 10^{22}$ years, $T_{1/2}(\beta \beta 0 \nu \to 2^+_1) > 1.6 \times 10^{23}$ years.