Investigation of double beta decay of 58Ni at the Modane Underground Laboratory

AbstraktAbstract

Investigation of double beta decay processes (β+EC, EC/EC) of 58Ni was performed at the Modane underground laboratory (LSM, France, 4800 m w.e.). A sample of natural nickel, containing ~68% of 58Ni and a mass of ~21.7 kg, was measured using ultra low-background HPGe detector Obelix (sensitive volume of 600 cm^3) during ~143.8 days. New experimental limits on 2νβ+EC decay of 58Ni to the ground 0+ and 2^+_(1), 811 keV excited state of 58Fe, and 2νEC/EC decay of 58Ni to 2^+_(1), 811 keV and 2^+_(2), 1 675 keV excited states of 58Fe were obtained in this measurement. There are -T1/2(β+EC, 0+ → 0+) > 1.7 × 10^22 y ;T1/2(β+EC, 0+ → 2+_(1)) > 2.3 × 10^22 y, T1/2(EC/EC, 0+ → 2+_(1)) > 3.3 × 10^22 y, T1/2(EC/EC, 0+ → 2+_(2)) > 3.4 × 10^22 y. For resonant neutrino-less radiative EC/EC decay with energy of 1 918.3 keV a new experimental limit of T1/2 (0νEC/EC – res, 1918KeV) > 4.1 ×10^22 y was also obtained. All limits are at 90 % CL.

Investigation of double beta decay processes (β+EC, EC/EC) of 58Ni was performed at the Modane underground laboratory (LSM, France, 4800 m w.e.). A sample of natural nickel, containing ~68% of 58Ni and a mass of ~21.7 kg, was measured using ultra low-background HPGe detector Obelix (sensitive volume of 600 cm^3) during ~143.8 days. New experimental limits on 2νβ+EC decay of 58Ni to the ground 0+ and 2^+_(1), 811 keV excited state of 58Fe, and 2νEC/EC decay of 58Ni to 2^+_(1), 811 keV and 2^+_(2), 1 675 keV excited states of 58Fe were obtained in this measurement. There are -T1/2(β+EC, 0+ → 0+) > 1.7 × 10^22 y ;T1/2(β+EC, 0+ → 2+_(1)) > 2.3 × 10^22 y, T1/2(EC/EC, 0+ → 2+_(1)) > 3.3 × 10^22 y, T1/2(EC/EC, 0+ → 2+_(2)) > 3.4 × 10^22 y. For resonant neutrino-less radiative EC/EC decay with energy of 1 918.3 keV a new experimental limit of T1/2 (0νEC/EC – res, 1918KeV) > 4.1 ×10^22 y was also obtained. All limits are at 90 % CL.