Measurement of the 2νββ decay half-life of 150Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector

We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope 150Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a complete background model for this isotope, including a measurement of the two-neutrino double-β decay half-life of T2ν 1=2 ¼ ½9.34 0.22ðstatÞ þ0.62 −0.60 ðsystÞ × 1018 y for the ground state transition, which represents the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay mechanisms. As no evidence for 0νββ decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the standard model. The observed lower limit, assuming light Majorana neutrino exchange mediates the decay, is T0ν 1=2 > 2.0 × 1022 y at the 90% C.L., corresponding to an upper limit on the effective neutrino mass of hmνi < 1.6–5.3 eV

Final results on ⁸²Se double beta decay to the ground state of ⁸²Kr from the NEMO-3 experiment

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ( 2\nu \beta \beta) half-life of ^{82}Se as T_{\smash {1/2}}^{2\nu } \!=\! \left[ 9.39 \pm 0.17\left( \text{ stat }\right) \pm 0.58\left( \text{ syst }\right) \right] \times 10^{19} y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is \left| M^{2\nu }\right| = 0.0498 \pm 0.0016. In addition, a search for neutrinoless double beta decay ( 0\nu \beta \beta) using 0.93 kg of ^{82}Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of T_{1/2}^{0\nu } > 2.5 \times 10^{23} \,\text{ y } \,(90\%\,\text{ C.L. }) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of \langle m_{\nu } \rangle < \left( 1.2{-}3.0\right) \,\text{ eV }, where the range reflects 0\nu \beta \beta nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other 0\nu \beta \beta mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set

A program for data analysis of rare fission mode processes from neutron-induced and spontaneous fissions

Rare fission mode processes (ternary or quaternary fission) of low-energy and spontaneous fission of heavy nuclei, in which light charged particles are emitted, are the subject of intense experimental and theoretical studies, since these studies can be attributed to one of the main sources of information on the mechanism of nuclear fission. To study these processes, a detection system has been assembled, consisting of three semiconductor ΔE-E telescopes and a silicon detector. In addition, the program has been developed for proceeding experimental data. This paper has been dedicated to the program written on the basis of ROOT software consisting of many scripts to analyze and/or filtrate ternary and quaternary fission particles among different fission events. The program can proceed long collected files in ASCII and binary formats, correlate results from all detectors, give results on particle interaction time, coordinates, particle energy and its types. The performance of the program has been tested to proceed ternary fission data from 252Cf spontaneous fission source

Present status of sensitive detector of reactor’s antineutrinos using scintillating detectors

In 2011, the reanalysis of the reactor antineutrinos spectra led to the formulation of the Reactor Antineutrino Anomaly (RAA) [1], which indicates the discrepancy between measured and expected antineutrino fluxes on short baselines. This discrepancy appears to favor the existence of the fourth “sterile” neutrino with |Δm2|&gt;1 eV2. To confirm or reject this hypothesis a high sensitive antineutrino detector located close to the reactor is required. In addition to that such a detector could be used to online monitor the isotopic composition of the reactor core and to prevent illegal production and removal of239Pu, which is the essential part of nuclear weapons.Detector DANSSino [2] already proved that even a compact antineutrino detector (∼ 1 m3) based on polystyrene is capable of antineutrino detection in the close vicinity of a reactor core (∼ 10 m) with signal to background ratio about one. As a common activity between JINR Dubna and IEAP CTU a new prototype of detector (called S3) has been proposed and is under construction. The construction design, selected results of Monte Carlo simulations and results of benchmark tests are presented

Gamma-ray spectroscopy with MAPD array in the readout of LaBr3:Ce scintillator

This paper presented a new detector module consisting of a micropixel avalanche photodiode (MAPD-3NM), LaBr3:Ce scintillator, and a compact read-out interface system for detecting gamma-rays in a wide energy range. The MAPD array (4 × 4 channels) was assembled using a singleMAPD-3NMcharacterized by its high photon detection efficiency (∼25%),pixel density (10 000 pixels/mm2), lowoperation voltage (74.5 V), and lowdark current. An active area of a singleMAPD-3NMwas 3.7 × 3.7 mm2, while this value was 17 × 17 mm2 for the assembled array with pixel density of 2190 000. The size of the tested LaBr3:Ce scintillator was 15 × 15 × 15 mm3. According to the characteristics of the detector module, a compact read-out interface device (SPECTRIG MAPD) was developed. SPECTRIG MAPD was designed as a miniature device with low power consumption, which continues to provide a wide spectrum of functions needed for measurement and test silicon photomultipliers (SiPM) and scintillation detectors on their basis. The various experiments were implemented to test the detection performance of a detector module to gamma radiation in the range from 30 keV to 4400 keV

Investigation of parameters of new MAPD-3NM silicon photomultipliers

In the presented work, the parameters of a new MAPD-3NM-II photodiode with buried pixel structure manufactured in cooperation with Zecotek Company are investigated. The photon detection efficiency, gain, capacitance and gamma-ray detection performance of photodiodes are studied. The SPECTRIGMAPD is used to measure the parameters of theMAPD-3NM-II and scintillation detector based on it. The obtained results show that the newly developedMAPD-3NM-II photodiode outperforms its counterparts in most parameters and it can be successfully applied in space application, medicine, high-energy physics and security