Registration Number
0223U004867,
(0123U102652)
, R & D reports
Title
Double beta decay of atomic nuclei
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Двонейтринний 2β-розпад 100Mo, результати для 150Nd, альфа-розпад 190Pt. Двонейтринний 2β-розпад 116Cd, альфа-розпад ізотопів осмію. 2ν2EC-розпад 106Cd, 0ν2β-розпад 116Cd, β-розпад 113Cd і константа gA. Різні 2β-процеси 106Cd, 0ν2β-розпад 100Mo, маса нейтрино.
Head
Kobychev Vladyslav V., Кандидат фізико-математичних наук
Registration Date
06-12-2023
Organization
Institute of Nuclear Research of the National Academy of Sciences of Ukraine
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The aim of the project is a search for the processes of double beta decay of 100Mo, 106Cd, 116Cd, 184Os, 190Pt nuclei at a new level of sensitivity, accurate measurement of the two-neutrino decay mode of 100Mo, 116Cd, 150Nd, and obtaining competitive estimates of Majorana neutrino mass, parameters of right-handed currents in weak interaction, neutrino interaction constants with majorons and some other parameters of models – extensions of the Standard Model of elementary particles. The abovementioned nuclides are among the most promising in terms of the probability of decay and the possibility of resonant neutrinoless double electron absorption. In addition to setting new neutrino mass limits on the level of 0.2-0.3 eV, the experiment with 100Mo will show the possibility of using low-temperature scintillation bolometric detectors in large-scale projects CUPID and AMoRE II with a sensitivity that will test the inverted neutrino mass state scheme. The aim of the project is also a search for double beta processes in the 106Cd nuclide and, possibly, the first observation of the two-neutrino electron capture with positron emission, as well as an estimation of the value of the axial-vector constant gA, for which the shape of the 113Cd beta spectrum should be measured with great accuracy and the decay scheme of 50V should be studied. The search for neutrinoless double electron capture should be performed in 106Cd, 186Os, and 190Pt nuclei, which have the possibility of a resonant transition (which should significantly increase the probability of decay and make it possible to estimate the neutrino mass and other parameters of the theory). An important additional goal of the project is development of experimental methods of low-background nuclear spectrometry for future, more sensitive studies.
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A new half-life limit T1/2 > 1.8 × 1024 yr is set for the 0ν2β decay of 100Mo, that corresponds to one of the strongest effective Majorana neutrino mass limits <m> < 0.28–0.49 eV. The half-life of 100Mo relative to the 2ν2β decay to the ground state of 100Ru is determined with the highest accuracy ±1.6%, the 2ν2β transition to the first 0+ excited level of 100Ru is observed with T1/2=(7.5±0.8(stat.)+0.4-0.3(syst.))×1020 yr. New lower limits for the half-lives of 106Cd, 100Mo, 150Nd, 184Os, 192Os, 190Pt, 198Pt relative to different channels and modes of the 2β decay were set on the level of T1/2 > (1014 - 1022) yr. The half-life of 150Nd relative to the 2ν2β transition to the first excited 0+ level of 150Sm is measured in two independent experiments as T1/2=(1.11+0.19-0.14(stat.)+0.17-0.15(syst.)) ×1020 yr (NEMO-3 tracking detector) and T1/2=(0.73+0.18-0.11(stat.)+0.16-0.17(syst.))×1020 yr (HPGe γ spectrometry). An evidence of the axial-vector coupling constant gA quenching with a factor of 0.655(2) as compared to the free-nucleon value gA = 1.276 is obtained with a high-resolution LiInSe2 bolometer. The half-life and beta-spectrum shape of 113mCd were measured, an optimized experiment to determine the 50V decay scheme was developed, to derive independent estimations of the constant gA. Low background detectors for study of double beta decay of 100Mo and 106Cd, naturally occurring zinc and tungsten nuclides, search for dark matter, detection of neutrino from supernova were developed and tested. New limits were set for α and 2α decay of the naturally occurring nuclides of neodymium and osmium on the level of T1/2 > 1016-1021 yr, the half-life of 190Pt relative to the α decay to the first excited level of the daughter was set as T1/2=(2.28+0.19-0.16(stat.) ±0.9(syst.))×1014 yr. A new upper limit on atomic abundance of hypothetical naturally occurring long-lived seaborgium (eka-tungsten, Z = 106) in tungsten was set as 5.1 × 10−15 atom (Sg) / atom (W).
Product Description
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Tretyak Volodymyr I.
Danevych Fedir A.
Kasperovych Dmytro V.
Sokur Nazar V.
Zarytskyi Mykola M
Klavdiienko Volodymyr R.
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2023-12-06
