Volume 80, Nº 3 (2016)

Analysis of the two-dimensional Dalitz plot measured in the reaction ¹⁴C(π^–, pd)X allows us to follow the absorption of pions by cluster ³p and identify signs of the configuration ³p + ¹¹Li in the ¹⁴C nucleus. The highly excited state of ^12,13Be beryllium isotopes with excitation energies E* ≈ 30 MeV and which decay with the emission of hydrogen isotopes is observed for the first time: ¹²Be* → p + ¹¹Li and ¹³Be* → d + ¹¹Li.

An experimental setup for studying the effects of N–N correlations in reaction d + ²H → n + n + p + p is described. It is planned to determine the energies of quasibound singlet states of two-nucleon systems (nn, pp, and np) under identical experimental conditions. The experiment is modeled numerically. The setup allows us to detect simultaneously the two nucleons (n + n, p + p, or n + p) resulting from the breakup of a quasi-bound state and a third particle (n or p). The characteristics of the setup’s detectors are investigated. A test experiment was carried out on reaction d + ²H → (pp) + (nn), with two protons and a neutron being detected.

A model equation obtained from the s-wave Faddeev equation in configuration space for three identical bosons by replacing the inhomogeneous integral term with a known function is studied. This function simulates the asymptotic decrease of the inhomogeneous term in the original Faddeev equation when y → ∞ as ∼y^–3/2. The asymptotes of the amplitude functions that approach the scattering amplitudes when y → ∞ are obtained analytically for the model equation using the Green function. It is shown that the asymptotics of the binary channel amplitude function oscillates. The similar oscillating behavior of the binary amplitude function is numerically demonstrated for the original s-wave Faddeev equation describing the neutron–deuteron scattering process.

Specific features of ⁴He interaction with light ⁹Be nuclei are studied. The potential of ⁴He–⁹Be interaction is calculated within the framework of the double folding model using the wave function of the ground state of the ⁹Be nucleus constructed in the three-cluster α + α + n approximation. The differential cross sections of elastic and inelastic ⁴He–⁹Be scattering and single-nucleon transfer in the intermediate range of energies are calculated. Comparative analysis of experimental and calculated results demonstrate their good agreement, indicating that the model assumptions on the cluster structure of ⁹Be nucleus are valid.

Differential cross sections of the elastic scattering of protons of intermediate energies by ⁹B and ¹⁰B nuclei are calculated within the Glauber theory. The matrix elements of elastic scattering are derived with a wave function in the three-particle 2αp-model (for ⁹B) and with an oscillatory wave function (for ¹⁰B). The differential cross-sections are calculated with allowance for the triple collisions on ⁹B nuclei and in the approximation of double collisions on ¹⁰B nuclei. The sensitivity of the differential cross-section to the ⁹B nucleus structure is analyzed. The differential cross section of ¹⁰B at E = 197 MeV is compared to the results from calculations using the distorted wave method.

A quantum coupled-channel approach with collective degrees of freedom (the rotation of deformed nuclei and/or their surface vibrations) is combined with an empirical coupled-channel model to add neutron rearrangement channels to vibrational and rotational excitations. The calculated fusion cross sections and the barrier distribution functions for several combinations of nuclei are in good agreement with experimental data.

An approximate approach that combines the algebraic versions of the resonating group model and the orthogonality conditions model is developed for description of radiative capture reactions. The approach is applied to the mirror ³H(α, γ)⁷Li and ³He(α, γ)⁷Be reactions. Astrophysical S-factors and branching ratios are calculated for these reactions. The nuclear interaction of the nucleons is described, using the modified Hasegawa–Nagata potential. The obtained results agree well with the experimental data, proving the applicability of the proposed approach to the describing radiative capture reactions and offering prospects for its further application.

The results from measuring the ²⁷Al(p, α)²⁴Mg reaction’s differential cross sections at E_p = 7.4MeV with the formation of the final nucleus in the ground and first excited (2⁺, 1.369 MeV) states are presented. The differential cross sections are obtained in the 25°–160° (lab) range of α-particle emission angles. Double-differential cross sections for the ²⁷Al(p, α₁γ)²⁴Mg reaction are measured at the same proton energy for several α-particle angles in the forward hemisphere. All even components of the density matrix spin tensors of the ²⁴Mg nucleus in the 2⁺ (1.369 MeV) state are reconstructed and its orientation characteristics are determined. The experimental results are compared with calculations for the triton pickup mechanism using coupled channels, and in the the statistical limit of the compound nucleus model.

The cross sections of partial photoneutron reactions are evaluated for the ^63,65Cu and ⁸⁰Se isotopes. The cross sections are free of systematic uncertainties from shortcomings of the experimental methods for neutron multiplicity sorting based on measurements of neutron energy used in experiments with quasimonoenergetic annihilation photon beams. An experimental-theoretical method is used to evaluate cross sections σ^eval(γ, in)= F_i^theor σ^exp(γ, xn), where ratios F_i^theor = σ^theor(γ, in)/σ^theor(γ, xn) = σ^theor(γ, in)/σ^theor[(γ, 1n) + 2(γ, 2n) + …] are calculated using a combined model of photonuclear reactions, and σ^exp(γ, xn) is the experimental cross section of the neutron yield reaction free from neutron multiplicity sorting problems. The cross sections are evaluated for reactions (γ, 1n) and (γ, 2n) for the ^63,65Cu and ⁸⁰Se isotopes, and for the total photoneutron reaction σ(γ, Sn) = σ[(γ, 1n) + (γ, 2n) + …]. It is shown that noticeable deviations of the experimental cross sections from the evaluated values result from the unreliable sorting of neutrons between the channels with multiplicities 1 and 2.

The source velocities (β = ν/c) extracted from rapidity plots of the fragment invariant probability distribution in terms of the longitudinal versus transversal velocity components has been studied for ⁴He + Au collisions at 4 and 14.6 GeV. It was found transition from broad range source velocities distribution in case of ⁴He(4 GeV) + Au to fixed source velocity in case of ⁴He(14.6 GeV) + Au.

The phase shift of the amplitudes of transmission of a coupled pair through the potential barrier and its reflection off it is investigated. It is shown that the amplitudes of all transitions have a pole singularity in the resonance energy region.

The hypothesis that part of solar electron neutrino flux transforms into antineutrinos of the second and third generations and related antiparticles is considered. Complete electroweak spectra of recoil electrons, including impurity components, are obtained and analyzed for the scattering of beryllium monoenergetic solar neutrinos with energies of 0.862 MeV on an electron target.