Search

Investigation of double beta decay processes (β+EC, EC/EC) of 74Se was performed at the Modane underground laboratory (LSM, France, 4800 m w.e.) using ultra low-background HPGe detector Obelix with sensitive volume of 600 cm³ and a sample of natural selenium with a mass of 1.6 kg, containing ∼0.89% (∼14.24 g) of 74Se. New experimental limits (at 90 % CL) on double beta decay transitions of 74Se to the ground and exited states of 74Ge were obtained from the preliminary calculation of experimental data accumulated in 135 days. [ABSTRACT FROM AUTHOR]

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.) using ultra low-background HPGe detector Obelix with sensitive volume of 600 cm3 and a sample of natural nickel, containing ∼68% of 58Ni with a mass of ∼21.7 kg. 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 from the preliminary calculation of experimental data accumulated in ∼88d. They are - T1/2(β+EC, 0+ → 0+) > 1.4 ×1021 y; T1/2 (β+EC, 0+ → 2+1 ) > 1.7 ×1022 y, T1/2 (EC/EC, 0+ → 2+1 ) > 2.4 ×1022 y, T1/2 (EC/EC,0+ → 2+2 ) > 2.1 × 1022 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) > 4.7 ×1022 y was also obtained. All limits are at 90 % CL. [ABSTRACT FROM AUTHOR]

A new experimental run of searching for EC/EC decay of 106Cd was performed at the Modane underground laboratory (4800 m w.e.) using the TGV-2 spectrometer and ~23.2 g 106Cd with enrichment of 99.57%. The limit on 2νEC/EC decay of 106Cd - T1/2(2νEC/EC) > 3.1×1020 y, at 90% C.L was obtained from the preliminary calculation of experimental data accumulated for 7018 h of measurement. The limits on the resonance neutrino-less double electron capture decay of 106Cd were obtained from the measurement of ~23.2 g of 106Cd with the low-background HPGe spectrometer OBELIX lasted 395 h - T1/2(KL, 2741 keV) > 0.9×1020 y and T1/2(KK, 2718 keV) > 1.4×1020 y at 90% C.L. [ABSTRACT FROM AUTHOR]

The SPT collaboration has been investigating the applicability of pixel detectors in the detection of two neutrino double electron capture (2νEC/EC) in 106Cd. The collaboration has proposed a Silicon Pixel Telescope (SPT) where a pair of Si pixel detectors with enriched Cd foil in the middle forms the detection unit. The Pixel detector gives spatial information along with energy of the particle, thus helps to identify and remove the background signals. Four units of SPT prototype (using 0.5 and 1 mm Si sensors) were fabricated and installed in the LSM underground laboratory, France. Recent progress in the SPT experiment and preliminary results from background measurements are presented. [ABSTRACT FROM AUTHOR]

Double beta decay (ββ) experiments are challenging frontiers in contemporary physics. These experiments have the potential to investigate more about neutrinos (eg. nature and mass). The main challenge for these experiments is the reduction of background. The group at IEAP, CTU in Prague is investigating a new approach using pixel detectors Timepix. Pixel detector offer background reduction capabilities with its ability to identify the particle interaction (from the 2D signature it generates). However, use of pixel detectors has some challenges such as the presence of readout electronics near the sensing medium and heat dissipation. Different aspects of pixel setup (identification of radio-impurities, selection of radio-pure materials) and proposed experimental setup are presented. Also, results of preliminary background measurements (performed on the surface and in the underground laboratories) using the prototype setups are presented. [ABSTRACT FROM AUTHOR]

The collaboration TGV has finished measurement of 2νEC/EC decay of 106Cd with 10 g (Phase I) and 13.6 g (Phase II) samples (with enrichment of 75%), respectively. The times of measurements were 8687h (Phase I) and 12900h (Phase II). The half-life limits (at 90% CL) were obtained for 2νEC/EC decay of 106Cd to the ground state of 106Pd as T1/2>3.0×1020 y (Phase I) and T1/2>4.2×1020 y (Phase II). The collaboration decided to continue with the study of 2νEC/EC decay of 106Cd using 23 g of an isotope enriched to 98.4%. We plan to use the TGV II spectrometer for this measurement and also Si pixel detectors for further study of double beta decay (ββ) processes. [ABSTRACT FROM AUTHOR]

The TGV II (Telescope Germanium Vertical) facility is a low background spectrometer operated in Modane Underground Laboratory. It aims at the study of double electron capture of 106Cd. The spectrometer is composed of 32 HPGe planar detectors interleaved with thin-foil samples made of Cd-106 enriched to 75% (total mass about 10 g). In 2006, the main run of phase I (1 year duration) was terminated yielding a new limit on half-life for two-neutrino double electron capture (g.s.→g.s.) in 106Cd as 2.0×1020 years. This limit is significantly higher (by almost three orders of magnitude) than those already published. [ABSTRACT FROM AUTHOR]