Search for double-beta decay of Ca-48 in NEMO-3 and commissioning of the tracker for the SuperNEMO experiment
The double-beta decay of Ca-48 was analysed with data taken by the NEMO-3 experiment with 6.99 grams of isotope and 1918.5 days of live time. The half-life of the two-neutrino double-beta decay of Ca-48 was measured to be 6.4 +0.6-0.7 (stat.) +1.2-0.9 (syst.) x 1019 years, with the corresponding nuclear matrix element measured to be 0.02 +- 0.002. A lower limit of 2.0 x 1022 years was placed on the half-life of the neutrinoless mode, yielding an upper limit on the effective Majorana neutrino mass of 6.1 - 38 eV. Limits were also placed on the R-parity violating supersymmetry trilinear coupling λ'111, on right-handed current couplings λ and η, and on the coupling of the Majoron to the electron neutrino. Work in preparation for the commissioning of the tracking detector for the SuperNEMO double-beta decay experiment is described. The data acquisition and high voltage supply electronics were prepared to read 504 SuperNEMO tracker cells and successfully tested with a smaller 2 x 9 array of tracker cells. A system to supply the SuperNEMO Demonstrator with the tracking gas mixture was designed and built with stringent radon emanation requirements. The system was shown to perform well on tests with a single-cell tracker prototype.