Investigation Of Double Beta Decay Research Articles

Heavy-ion induced double charge exchange reaction in a multi-channel approach: The research program of the NUMEN project

We give an updated view of the status and prospects of heavy-ion double charge exchange (HI-DCE) reaction studies performed at the Laboratori Nazionali del Sud of the Istituto Nazionale di Fisica Nucleare (INFN-LNS) in the context of the NUMEN project. The important role of HI-DCE for nuclear reaction, nuclear structure and double beta-decay investigations is outlined. A powerful way to scrutinize the nuclear response to HI-DCE is to consistently link it to the information extracted from the competing direct reactions pointing to a multi-channel description of the whole network of quasi-elastic processes. Indeed, these complementary studies are mandatory in order to minimize the systematic errors in the data analyses and build a many-facets and parameter-free representation of the systems under study.

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

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 cm3) during ∼143.8 days. New experimental limits on 2νβ+EC decay of 58Ni to the ground 0+ and (math), 811 keV excited state of 58Fe, and 2νEC/EC decay of 58Ni to (math), 811 keV and (maht), 1 675 keV excited states of 58Fe were obtained in this measurement. There are -T1/2(β+EC, 0+ → 0+) > 1.7 × 1022 y; (math), (math), (math). 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 ×1022 y was also obtained. All limits are at 90 % CL.

Double-beta decay investigation with highly pure enriched [Formula: see text]Se for the LUCIFER experiment.

The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of ^{82}Se. The matrix which embeds the source is an array of ZnSe crystals, where enriched ^{82}Se is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3 % enriched ^{82}Se metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of ^{232}Th, ^{238}U and ^{235}U are respectively: <61, <110 and <74 mu Bq/kg at 90 % C.L. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the ^{82}Se allowed us to establish the most stringent lower limits on the half-lives of the double-beta decay of ^{82}Se to 0^+_1, 2^+_2 and 2^+_1 excited states of ^{82}Kr of 3.4cdot 10^{22}, 1.3cdot 10^{22} and 1.0cdot 10^{22} y, respectively, with a 90 % C.L.

Investigation of double beta decay of 100Mo to excited states of 100Ru

Double beta decay of $^{100}$Mo to the excited states of daughter nuclei has been studied using a 600 cm$^3$ low-background HPGe detector and an external source consisting of 2588 g of 97.5% enriched metallic $^{100}$Mo, which was formerly inside the NEMO-3 detector and used for the NEMO-3 measurements of $^{100}$Mo. The half-life for the two-neutrino double beta decay of $^{100}$Mo to the excited 0$^+_1$ state in $^{100}$Ru is measured to be $T_{1/2}=[7.5 \pm{0.6}(stat) \pm {0.6}(syst)]\cdot 10^{20}$ yr. For other $(0\nu + 2\nu)$ transitions to the 2$^+_1$, 2$^+_2$, 0$^+_2$, 2$^+_3$ and 0$^+_3$ levels in $^{100}$Ru, limits are obtained at the level of $\sim (0.25-1.1)\cdot 10^{22}$ yr.

Coincidence Techniques in Gamma-ray Spectroscopy

Abstract In many different gamma-ray detection systems, the events are registered in coincidence, i.e. within short time interval, by two or more detectors. Depending on purpose of an experiment, these events can be rejected (anticoincidence counting) or acquired (coincidence counting). The construction, setup and application of several coincidence systems in Laboratory for nuclear physics of Department of Physics in Novi sad are presented. The anti-Compton shield for HPGe detector based on big annular NaI(Tl) detector and corresponding measurement which proved existing of 283 keV level in Ba-137 populating by beta decay of Cs-137, is described. The application of this system (in addition with NaI(Tl) plug detector) where HPGe detector is actively shielded by NaI(Tl) detector for investigation of double beta decay of positron emitters (Cr-50, Zn-64,) is also shown. The improving of detection limit of HPGe detector by the active shield consisting of five plastic scintillation detectors is presented, as well as the measurements of cross sections for X-ray production, induced by interaction of cosmic-ray muons with massive lead shield. We found that the prompt and delayed coincidence events between plastic veto detector and Ge detector can be sharply divided in two groups. Also, the bremsstrahlung and annihilation events can be time resolved from (n,n’) events, although all these events belong to the group of delayed events.

Investigation of double-beta decay with the NEMO-3 detector

The double beta decay experiment NEMO~3 has been taking data since February 2003. The aim of this experiment is to search for neutrinoless ($0\nu\beta\beta$) decay and investigate two neutrino double beta decay in seven different isotopically enriched samples ($^{100}$Mo, $^{82}$Se, $^{48}$Ca, $^{96}$Zr, $^{116}$Cd, $^{130}$Te and $^{150}$Nd). After analysis of the data corresponding to 3.75 y, no evidence for $0\nu\beta\beta$ decay in the $^{100}$Mo and $^{82}$Se samples was found. The half-life limits at the 90% C.L. are $1.1\cdot 10^{24}$ y and $3.6\cdot 10^{23}$ y, respectively. Additionally for $0\nu\beta\beta$ decay the following limits at the 90% C.L. were obtained, $> 1.3 \cdot 10^{22}$ y for $^{48}$Ca, $> 9.2 \cdot 10^{21}$ y for $^{96}$Zr and $> 1.8 \cdot 10^{22}$ y for $^{150}$Nd. The $2\nu\beta\beta$ decay half-life values were precisely measured for all investigated isotopes.

Search for double beta decay of 106Cd in the TGV-2 experiment

An investigation of double beta decay (β+β+, β+/EC, EC/EC) of 106Cd was performed at the Modane underground laboratory (at a water equivalent depth of 4800 m) using a TGV-2 spectrometer with 32 detectors. Evaluation of the experimental data accumulated over 12 400 h of measuring ∼13.6 g of 106Cd with an enrichment of 75% was performed. New limits (at a confidence level of 90%) on the half-lives of the 0νEC/EC resonant decay of 106Cd to the 2741 keV excited state of 106Pd − T1/2 ≥ 1.5 × 1020 y and on 2νEC/EC decay to the ground state of 106Pd (0+ → 0+, g.s.) − T1/2 ≥ 3.9 × 1020 y were obtained. The limits of the 2νEC/EC decay of 106Cd to the 2+, 512 keV and 01+, 1334 keV excited states of 106Pd and 2νβ+β+- and the 2νβ+EC decays of 106Cd to the ground and excited states of 106Pd were improved.

Investigation of double-beta decay at the Institute of Theoretical and Experimental Physics (ITEP, Moscow)

Investigation of neutrinoless double-beta (2{beta}0{nu}) decay is presently being considered as one of the most important problems in particle physics and cosmology Interest in the problem was quickened by the observation of neutrino oscillations. The results of oscillation experiments determine the mass differences between different neutrino flavors, and the observation of neutrinoless decay may fix the absolute scale and the hierarchy of the neutrino masses. Investigation of 2{beta}0{nu} decay is the most efficient method for solving the problem of whether the neutrino is a Dirae or a Majorana particle, Physicists from the Institute of Theoretical and Experimental Physics (ITEP, Moscow) have been participating actively in solving this problem. They initiated and pioneered the application of semiconductor detectors manufactured from enriched germanium to searches for the double-beta decay of {sup 76}Ge. Investigations with {sup 76}Ge provided the most important results. At present, ITEP physicists are taking active part in four very large projects, GERDA. Majorana, EXO, and NEMO, which are capable of recording 2{beta}0{nu} decay at a Majorana neutrino mass of {approx} 10{sup -2} eV.

Background structure in the Heidelberg-Moscow experiment on the search and investigation of double beta decay of 76Ge1

Independent analysis of the spectra from the Heidelberg-Moscow experiment has been carried out. A direct comparison of the peak intensities in the spectra allows for the conclusion that in the energy range up to 3200 keV the background is due to the detection of γ rays from the decay of trace impurities of anthropogenic and cosmogenic nuclides occurring in the apparatus between the HPGe detectors and the main (Pb and Cu) shielding. The 226Ra, 214Pb, and 214Bi γ rays observed in the spectra are shown to arise in the 226Ra rather than 238U decay chain. The estimates of the expected intensities of the weak 214Bi γ rays in the spectrum region around Qββ(76Ge) = 2039 keV do not contradict the observation of the peak at 2039 keV as claimed by Klapdor-Kleingrothaus and coauthors.

Germanium cryogenic detectors: Alpha surface events rejection capabilities

Alpha surface events and multiple compton gamma interactions are the two major background components in Ge detectors for double-beta decay investigations. Two different methods have been studied to identify such type of events, using cryogenic Ge detectors developed primarily for dark matter search: (i) combined heat and ionization measurements, and (ii) pulse-shape analysis of the charge collection signals. Both methods show strong separation between electron recoil events and surface alphas. Cryogenic heat-ionization detectors therefore appear able to reject virtually all surface alpha interactions.

NUCLEAR DOUBLE-BETA DECAY AND NEUTRINO MASSES

The double-beta decay process has been widely investigated in the last two decades due to the possible lepton number nonconservation decay modes that may occur. An experimental evidence of these modes would lead to the conclusion that neutrino is a massive Majorana particle. At present, when the nonzero neutrino mass is convincingly proved by neutrino oscillation experiments, the double-beta decay investigations are the most promising for determining the absolute value of the neutrino mass. In this paper we give a brief review of some recent nuclear double-beta decay investigations in connection with neutrino mass. We discuss the potential of this process to search for beyond standard model physics, the QRPA-based methods for computing the relevant nuclear matrix elements and the derivation of neutrino masses both from double-beta decay and neutrino oscillation data and in agreement with the present cosmological constraints.

Investigation of double beta decay of 82Se and 96Zr with tracking detector NEMO-2

To investigate double beta decay processes the NEMO collaboration developed an electron tracking detector made of Geiger cells for track reconstruction and plastic scintillators for energy measurements. The prototype, NEMO-2, is described and results on ββ decay of 82Se and 96Zr are given.

Track experiment for the double beta decay investigation of the different isotopes

TPC in magnetic field had been proposed to search for the neutrinoless double beta decay of the different isotopes. First stage of this program was the prototype TPC with volume 0.3m 3 . 150 Nd 2β2v decay with half-life time T 1/2 (2β2v) = (1.88 ± 0.39 0.69 ± 0.19) · 10 19 years was observed. There was shown the powerful ability of the track experiment to suppress the background. The rejection factor k > 10 7 was obtained at the laboratory on the sea level. The large setup (TPC with volume 13m 3 in the magnet with diameter d=5.5m) is under construction

Double beta decay in 48Ca and the conservation of leptons

Abstract A new experimental investigation of double beta decay in 48Ca using apparatus of unique sensitivity and discrimination is reported. We obtain a lower limit of 1.6 × 1021 years at a statistical confidence level of 80% for the lifetime of the lepton-nonconserving neutrinoless mode, and of 3 × 1019 years for the lepton-conserving two-neutrino mode.