Search

Axions with an energy of 8.4 keV emitted in the М1 transition in 169Tm nuclei in the Sun are sought in the → 169Tm* → (8.4 keV) reaction of resonant absorption by 169Tm nuclei on the Earth using a thulium garnet crystal as a bolometric detector. The flux of monochromatic 8.4‑keV axions has been calculated. New constraints on the axion–nucleon coupling constants have been obtained and, as a result, new upper bounds on the axion mass eV and eV have been obtained at 90% C.L. in the KSVZ and DFSZ models, respectively. [ABSTRACT FROM AUTHOR]

Operation of a model of a compact neutron source that can be used to calibrate dark-matter and electron-antineutrino detectors and to determine their response functions is demonstrated. The calibration neutron source in question is a combination of the Cf radionuclide, which undergoes spontaneous fission, producing neutrons, and an original silicon semiconductor detector. The latter provides a time reference for the neutron-emission instant by recording signals from fission fragments. [ABSTRACT FROM AUTHOR]

The resonant excitation of the 83Kr first excited nuclear level (E = 9.4 keV) by solar axions whose fluxes depend on the axion–electron coupling constant gAe is sought. The γ- and X-ray photons and the conversion and Auger electrons from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences). As a result, a new constraint ≤ 1.50 × 10–17 (90% C.L.) has been obtained for the axion–electron and axion–nucleon coupling constants, which corresponds to new constraints on the axion mass mA ≤ 320 eV and mA ≤ 4.6 eV in the KSVZ and DFSZ axion models, respectively. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022390011 [ABSTRACT FROM AUTHOR]

A 4π β spectrometer consists of two Si(Li) detectors with a sensitive region that is more than 8-mm thick. Using this total-absorption spectrometer it is possible to make a direct measurement of β spectra without correcting the response function for the electron backscattering from the crystal surface. The β spectra of transitions to the excited states of daughter nuclei have been measured using an additional 3'' BGO detector of γ rays, which is connected in coincidence with the pair of Si(Li) detectors. [ABSTRACT FROM AUTHOR]

A spectrometer based on a Si(Li) detector has been tested by exposure to α particles with the aim of determining changes in the detector characteristics versus the fluence. As a result of 60-day measurements with a total fluence of 6.2 × 109 α particles, it has been established that the dependence of the deterioration in the energy resolution of α-particle peaks on the fluence is described by a linear function with a slope of Δσ/ΔФ = (8.4 ± 0.4) × 10–10 keV/α. The measured amplitude of the α-particle momentum decreases linearly with increasing fluence with a slope of (–4.8 ± 0.6) × 10–9 keV/α. These effects do not prevent reliable discrimination between the signals from α particles and fission fragments until the fluence reaches a value of 1010 α particles when the Si(Li) detector is a part of a neutron source for detecting fission fragments. [ABSTRACT FROM AUTHOR]

Spectra of electrons from beta decays of 144Ce-144Pr nuclei have been measured and analyzed in order to find a contribution from a heavy neutrino. For the neutrino with the mass mνH in the interval of 150-350 keV, a new upper bound |UeH|2 ≤ (2−5) × 10−3 at 90% C.L. has been found for the mixing parameter. [ABSTRACT FROM AUTHOR]

Resonance excitation of the 83Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion-photon coupling constant and the axion mass:|gAγ × mA| ≤ 6.3 × 10 -17 In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of mA ≤ 12.7 eV at 95% C.L. [ABSTRACT FROM AUTHOR]

The characteristics of a beta spectrometer that consists of a total-absorption Si(Li) detector and a drift Si detector are presented. Using this spectrometer, it is possible to efficiently separate β radiation of nuclei from concomitant X and γ rays. The method is based on coincidences between signals from the thick and thin detectors. The spectrometer can be used to precisely measure the shape of the β spectra of various radioactive nuclei, in particular, of the 144Pr nucleus, which is the most promising antineutrino source for searching for neutrino oscillations into a sterile state. [ABSTRACT FROM AUTHOR]

A method for calibrating the energy scale of a scintillation detector using γ rays has been proposed and implemented. The technique is based on Compton scattering in the scintillation detector, followed by photoelectric absorption of a scattered γ-ray photon in a Ge detector. The novelty of the method consists in placing the γ-ray source and the scintillation and Ge detectors tightly to each other. The method is efficient for detectors with a low-Z material for which the ratio of the cross sections for Compton scattering and photoeffect is great in value and the attenuation length of the γ-ray flux is comparable to the detector dimensions. The described technique can be used to precisely investigate the dependence of the light yield in a scintillator on the electron energy. [ABSTRACT FROM AUTHOR]

Axions with an energy of 9.4 keV emitted in the M1 transition of Kr nuclei in the Sun have been sought in the resonance absorption reaction A + Kr → Kr* → Kr + γ, e (9.4 keV). A proportional gas chamber filled with krypton and placed in a low-background setup at the underground laboratory of the Baksan neutrino observatory was used to detect γ-ray photons and electrons appearing after the decay of a nuclear level. As a result, a new constraint has been determined on the isoscalar and isovector coupling constants of the axion with nucleons: | g- g| ≤ 1.29 × 10. This constraint results in the following new bound on the mass of the axion in the hadronic axion model: m ≤ 100 eV (95% C.L.). [ABSTRACT FROM AUTHOR]

xions of energy 14.4 keV that originated from the M1 transition in Fe nuclei in the Sun were sought by using the resonance-absorption reaction A+Fe → Fe* → Fe+ γ (14.4 keV). Asectioned Si(Li) detector arranged in a low-background facility was used to record photons from this reaction. This resulted in setting a new limit on the axion couplings to nucleons, |−1.19 g + g| ≤ 3.0×10. Within the hadronic-axion model, the respective constraint on the axion mass is m ≤ 145 eV (at a 95% C.L.). [ABSTRACT FROM AUTHOR]

We searched for resonant excitation of the first excited state of the 169Tm nucleus by axions formed inside the Sun by the Primakoff effect, A + 169Tm → 169Tm* → 169Tm + γ (8.41keV). Gamma quanta with an energy of 8.41keV were registered by a sectionalized Si(Li) detector installed in a low-background setup. As a result, we set a new upper limit for the photon to axion coupling constant, g Aγ(GeV−1) m A(eV) ≤ 1.06 × 10−5, which for a hadronic axion model corresponds to a mass limit of m A ≤ 169 eV at a 90% confidence level. [ABSTRACT FROM AUTHOR]

A search for resonant absorption of 14.4 keV solar axions by a 57Fe target was performed. The Si(Li) detector placed inside the low-background setup was used to detect the γ-quanta appearing in the deexcitation of the 14.4 keV nuclear level: A+57Fe→57Fe*→57Fe+ γ. The new upper limit for the hadronic axion mass has been obtained of m A≤159 eV (95% c.l.) ( S=0.5, z=0.56). [ABSTRACT FROM AUTHOR]

The resonant absorption of solar axions by 57Fe nuclei, which is accompanied by the excitation of the first excited nuclear level: A + 57Fe → 57Fe* → 57Fe + γ(14.4 keV), is sought. To seek 14.4-keV photons, a Si(Li) detector and an enriched 57Fe target are used. The detector and target are placed in a low-background setup equipped with passive and active shieldings. As a result, a new upper limit m A ≤ 360 eV (at 90% C.L.) has been determined for the axion mass. [ABSTRACT FROM AUTHOR]