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Vol 87, No 6 (2024)
ЯДРА. Теория
THE SEPARABLE FORCES APPROXIMATION IN THE GENERALIZED THEORY OF FINITE FERMI SYSTEMS
Abstract
The separable forces approximation is applied for the first time to the generalized theory of finite Fermi systems (TFFS), which was developed in the works [1–4] in order to consistently account for complex configurations with phonons within the framework of the Green’s function method. Standard multipolemultipole forces are used, and for their quadrupole case, two parameters are adjusted according to the known quadrupole effective polarization charges, which are well known in the experiment and in the standard TFFS. It is shown that in this approximation, the equations of the standard TFFS for the vertex and the total amplitude are easily solved. A useful relationship has been obtained between effective quadrupole polarization charges and the parameters of separable forces, which describe the full amplitude in a separable form. As an application of our approach, the equation for the regular part of the Γ amplitude was studied for the first time. Both free terms of this equation are estimated and it is shown that the additional term containing the product of two phonon creation amplitudes is several times higher than the other free term, which is the effective interaction of TFFS, taken in a separable approximation. The obtained solutions of the equation for Γ lead to the conclusion that this value cannot be neglected. Since Γ naturally appears in the generalized TFFS to describe two-phonon excitations, this means that the theory of two-phonon excitations can become noticeably more complicated.
Âdernaâ fizika. 2024;87(6):451-459
451-459
52Cr PHOTONEUTRON REACTIONS IN EXPERIMENTS WITH BREMSSTRAHLUNG
Abstract
The reliability of data of (γ, 1 ) and (γ, 2 ) reactions on 52Cr obtained in experiment on the beam of bremsstrahlung using the corrections to the neutron yield cross section σ(γ, ) = σ(γ, 1 ) + 2σ(γ, 2 ) calculated via statistical theory was investigated. Using the experimental-theoretical method for evaluation of photoneutron partial reaction cross sections based on objective physical criteria it was shown that partial reaction cross sections obtained do not satisfy physical criteria of reliability. Experimental cross section of the reaction 52Cr(γ, 1 )51Cr is unreliably significantly underestimated, but that of reaction 52Cr(γ, 2 )50Cr – on the contrary is overestimated in comparison with evaluated ones. It is shown that it is the results of the shortcomings of the method for obtaining information about cross sections of partial reactions. The main reason is the disregard of the contribution of two-nucleon reaction (γ, 1 1 ) main features (energy position and amplitude) whose cross section compete with those of also two nucleon reaction (γ, 2 ) though multiplicities of neutrons from those reactions are different.
Âdernaâ fizika. 2024;87(6):460-468
460-468
MODELING OF THE DOPPLER BROADENING EFFECT IN THE REACTION 16O(n,αγ)13C TAKING INTO ACCOUNT THE SLOWING DOWN OF THE 13C* ION
Abstract
Doppler broadening of the γ-lines of the secondary ion 13C*, produced in the 16O(n, αγ)13C reaction induced by neutrons interacting with the beryllium oxide target, is calculated within the framework of the LSS model for the stopping power of the low energy ions. The 16O(n, αγ)13C cross-sections are calculated by the quark-level nuclear reactions model CHIPS. It is shown that for not too short and not too long lifetimes of the excited γ-levels the slowing down of the radioactive ions defines shapes of the measured γ-lines.
Âdernaâ fizika. 2024;87(6):469-471
469-471
BINDING ENERGIES OF 3H, 3He NUCLEI IN THREE-BODY FADDEEV EQUATIONS WITH DIRECT INTEGRATION
Abstract
The paper presents a new method for searching for binding energies of three-body systems based on the numerical solution of a system of homogeneous Faddeev equations with respect to the matrix T with direct numerical integration without the traditional partial wave decomposition. In this paper, we tried to demonstrate on the simplest systems with three point nucleons the features of the numerical solution of homogeneous Faddeev equations, two-body 𝑡-matrices in which both local and non-local potentials are generated. The characteristic behavior of the binding energies of three bodies has been established depending on the change in the number of nodes of the radial grid of relative momenta. The paper compares the method of Pade approximants and the algebraic method of matrix inversion in the numerical solution of the Lippmann–Schwinger equations. It is shown that both methods can be used in problems of searching for binding energies of systems of three bodies. In the chosen numerical scheme, the influence of Coulomb repulsion and the three-body 𝑁𝑁𝑁 force on the binding energies of the systems under consideration is estimated. It is shown that the missing 𝑁𝑁𝑁 interaction must be charge-dependent in order to explain the skew in the missing contributions to the binding energies of the 3He, 3H nuclei under consideration at the level of 143 keV.
Âdernaâ fizika. 2024;87(6):472-485
472-485
ANALYSIS OF INELASTIC SCATTERING OF POLARISED PROTONS ON 54,56Fe NUCLEI
Abstract
The paper analyzes the results of experiments on inelastic scattering of polarized protons on 54.56Fe nuclei. The work presents for the first time differential cross sections and analyzing power for levels 21+, 22+, 41+, 42+ for the scattering of protons with energy of 16 MeV. Published experimental data for the same levels, but for proton energies of 18.6 and 400 MeV are also analyzed. Calculations of inelastic scattering observables were performed using the coupled channel method for proton energy 16 and 18.6 MeV and the distorted wave method for proton energy of 400 MeV. The predictions of two collective models of excited states of the nucleus were compared: the asymmetric rotator model and the multiphonon vibrational model. In addition, the wave functions of excited states calculated using the shell model were tested.
Âdernaâ fizika. 2024;87(6):486-499
486-499
ЭЛЕМЕНТАРНЫЕ ЧАСТИЦЫ И ПОЛЯ. Эксперимент
LOOKING FOR GEO-ANTINEUTRINO FLUX FROM 40K USING BOREXINO DATA
Abstract
The Borexino detector can detect antineutrino fluxes as well as solar neutrinos fluxes using neutrinoelectron scattering reaction. Antineutrino fluxes are produced inside the Earth by isotopes of natural radioactivity and on the Earth’s surface by reactor cores of nuclear power plants. We analyzed the latest data from the Borexino detector adding to the analysis of solar neutrino fluxes the antineutrino ones, adding them to the known backgrounds. The result of the analysis was that non-zero antineutrino flux from 40K was found. At the same time, all solar neutrino fluxes began to be consistent with the low metallicity Sun model.
Âdernaâ fizika. 2024;87(6):500-504
500-504
СORRELATION ANALYSIS BETWEEN GAMMA QUANTA COUNTING RATE ON LVD FROM NATURAL RADIOACTIVITY AND ATMOSPHERIC PRESSURE
Abstract
This work investigates the effect of atmospheric pressure on the counting rate of gamma quanta from natural radioactivity, measured in continuous monitoring mode on a Large Volume Detector (LVD). Emissions in the time series of gamma quanta are associated with the emanation of radon from the rock in the underground room of the experimental hall. As a result of the analysis of hourly data, no direct connection was found between the change in pressure and the counting rate of gamma rays. During sharp drops in pressure, no delayed pumping effect was detected for gamma rays. A strong anti-correlation between the trends in changes in the gamma-ray counting rate and pressure was discovered on scales of the order of 3–4 months.
Âdernaâ fizika. 2024;87(6):505-512
505-512
STUDY OF THE 𝑒+𝑒- → π+π-π0 PROCESS DYNAMICS IN THE ENERGY RANGE 1.075–1.975 GeV
Abstract
The 𝑒+𝑒− → π+π−π0 process was studied in the energy range from 1.075 to 1.975 GeV basing on the data with an integral luminosity of about 70 pb−1, accumulated in the experiment with the SND detector at the 𝑒+𝑒− collider VEPP-2000. Dalitz distributions were analyzed in a model including the intermediate states ρ(770)π, ρ(1450)π and ωπ0. As a result, the energy dependences of the total cross section of the process 𝑒+𝑒− → π+π−π0, cross sections for intermediate states ρ(770)π and ρ(1450)π and the relative phases between the amplitude ρ(770)π and the amplitudes ρ(1450)π and ωπ0 were measured. In the vector dominance model, for the first time it was carried out joint approximation of the cross sections 𝑒+𝑒− → ρ(770)π and ρ(1450)π and the relative phase between the amplitudes of these states. The contributions of the ω, ϕ, ω(1420) and ω(1650) resonances were taken into account. As a result of the approximation, it was found that the decay ω(1650) → π+π−π0 goes mainly through the intermediate state ρ(1450)π, while in the decay of ω(1420) → π+π−π0 the ρ(770)π mechanism dominates. The obtained results clarify the previous measurement of the SND.
Âdernaâ fizika. 2024;87(6):513-524
513-524
MEASUREMENT OF THE ANALYZING POWER OF 𝑝𝑝 AND 𝑝𝑝 ELASTIC SCATTERING AT THE SPASCHARM FACILITY AT U-70
Abstract
The study of spin effects in elastic proton-proton and antiproton-proton scattering in the SPASCHARM experiment at U-70 accelerator facility (NRC “Kurchatov institute” – IHEP, Protvino) is discussed. Polarized beams or a polarized target of the experiment will be used to measure the analyzing power 𝐴𝑁 of elastic scattering of protons and antiprotons. The possibility of using two different types of the detectors to register recoil particles of elastic scattering of protons is analyzed. In the first case, it is proposed to use scintillation counters, the second option is a detector based on proportional chambers. A comparison of the registration efficiency of elastic 𝑝𝑝-scattering for two configurations of the experimental setup is carried out, and the required measurement time is determined.
Âdernaâ fizika. 2024;87(6):525-530
525-530
MEASUREMENT OF CROSS-SECTION OF THE 7Li(𝑑, 𝑛)8Be REACTIONS AT THE DEUTERON ENERGIES FROM0.4 to 2.1 MeV
Abstract
Obtaining intense neutron fluxes are required for production of radioactive isotopes, radiation testing of promising materials, neutron diffraction, neutron capture therapy and other applications. The interaction of deuterons with lithium is characterized by a high neutron yield, a wide variety of reactions, but the available experimental data on the reaction cross-section are scarce and contradictory, which does not allow reliable estimation of the yield and spectrum of generated neutrons. In this work, effective partial cross-sections of the nuclear reactions 7Li(𝑑, 𝑛)8Be with the formation of the Be nucleus in the ground and first excited states at deuteron energies from 0.4 to 2.1 MeV were measured at accelerator based neutron source VITA using developed RBN-A1 fast neutron spectrometric radiometer. It is shown that measurements by the fast detector radiometer with two diamond spectrometric detectors provide a number of advantages over the traditionally used measuring path scintillation detector. Analysis of the high-energy part of the amplitude spectra of diamond detectors, determined by the reactions 12C(𝑛, α)9Be and 12C(𝑛, α)9Be*, made it possible to measure the effective partial cross sections of the nuclear reaction 7Li(𝑑, 𝑛)8Be with the formation of the Be nucleus in the ground and especially in the first excited state.
Âdernaâ fizika. 2024;87(6):531-543
531-543
INTERNAL BACKGROUND FROMTWO NEUTRINO DOUBLE BETA DECAY IN SEARCH FOR NEUTRINOLESS DOUBLE BETA DECAY 150Nd
Abstract
The internal background of the detector arising during the search for neutrineless double beta decay of the isotope 150Nd, from two neutrino beta decay of the same isotope, has been calculated. The calculation was performed for a detector based on liquid neodymium containing organic scintillator with a volume of several liters at various detector configurations and Nd concentrations up to 5.5 g/l. Limits on the sensitivity of the detector in searching for neutrineless double beta decay of isotope 150Nd have been obtained.
Âdernaâ fizika. 2024;87(6):544-549
544-549
MEASUREMENT OF RADIOACTIVITY OF MATERIALS FOR LOW-BACKGROUND EXPERIMENTS USING A SEMICONDUCTOR GAMMA-RAY SPECTROMETER
Abstract
To create a prototype of a detector based on a neodymium-containing liquid organic scintillator for the search for neutrinoless double beta decay of 150Nd, measurements of the spectra of radioactive impurities from various materials used in the manufacture of the detector were carried out using low-background semiconductor gamma spectrometers at the Baksan Neutrino Observatory INR RAS. The potential use of 3D printing in low-background conditions was considered. This could potentially allow the creation of detector structural elements with a record-low content of radioactive impurities for experiments in neutrino astrophysics, dark matter searches, neutrinoless double-beta decay experiments. The activity of radioactive impurities in plastic parts produced on a 3D printer, which were intended for use in creating a prototype of a detector and its low-background shielding, were measured. ЯДЕРНАЯ
Âdernaâ fizika. 2024;87(6):550-558
550-558
MODELLING OF THE NEUTRINO TAGGING SYSTEM FOR THE NEAR DETECTOR IN THE P2O EXPERIMENT
Abstract
This paper describes the method of neutrino tagging in neutrino experiments and the principles of its realization. The neutrino tagging method consists in the kinematic reconstruction of the neutrino formation reaction – the decay π±( ±) → µ± + νµ(νµ) – by measuring the parameters of the charged particles – parent meson and muon – using a tagging station. This allows us to recover the energy, direction and point of neutrino formation with a high accuracy. A description of the neutrino tagging method and the potential advantages of the resulting beam for short-base experiments are presented. The scheme of the neutrino tagging station is considered and its operation is modeled.
Âdernaâ fizika. 2024;87(6):559-570
559-570
RELATIVISTIC EQUATION FOR A FOUR-NUCLEON SYSTEM
Abstract
The paper generalizes the four-particle integral Faddeev–Yakubovsky equation to the relativistic case. The obtained system of integral equations is solved by the iteration method and the binding energy and amplitudes of states of the helium-4 nucleus are found. The rank-one separable Yamaguchi potential is used as the interaction potential. In the calculations the only states with zero orbital momentum are considered – states. The results of the calculation are compared with non-relativistic calculations and experimental value.
Âdernaâ fizika. 2024;87(6):571-576
571-576