Abstract
The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of ^{100}Mo to the ground state of ^{100}Ru, T_{1/2} = left[ 6.81 pm 0.01,left( text{ stat }right) ^{+0.38}_{-0.40},left( text{ syst }right) right] times 10^{18} year. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of 5times 10^5 events and a signal-to-background ratio of sim 80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of mathrm{n}=2,3,7, as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained.
Highlights
Spontaneous nuclear double beta decay is a second order weak interaction process that was theoretically considered for the first time by Goeppert-Mayer [1]
The results of the 2νββ decay of 100Mo with the full data set of the NEMO-3 experiment corresponding to a 34.3 kg×year exposure are presented
The summed energy of two electrons, the single electron energy and the angular distributions between the two electrons have been studied with an unprecedented statistical precision (5 × 105 events)
Summary
Spontaneous nuclear double beta decay is a second order weak interaction process that was theoretically considered for the first time by Goeppert-Mayer [1]. It can occur in some even-even nuclei when two bound neutrons simultaneously undergo beta decay and are transformed into two bound protons emitting two electrons and two (anti)neutrinos. Detailed studies of 2νββ may be useful to improve NME calculations for the neutrinoless mode of double beta decay, 0νββ, the process which violates total lepton number and is one of the most sensitive probes of physics beyond the Standard Model. The impact of the single electron energy spectra on nuclear models that are used to calculate the NME is presented. In this paper we present results obtained for 100Mo 0νββ decay accompanied by the emission of Majoron bosons with spectral indices n ≥ 2, as well as constraints on contributions from bosonic neutrinos and from Lorentz invariance violation to 2νββ spectra of 100Mo
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