Pion scattering on 3H and 3He nuclei in the Δ33(1232) region

Elastic scattering of π ^± mesons on ³H and ³He nuclei at energies around the Δ₃₃(1232) resonance is considered. The amplitudes for single and double scattering are calculated on the basis of the nonrelativistic diagram technique. The spin and isospin structure of pion-nucleon amplitudes is fully taken into account. The resulting theoretical predictions for the differential cross sections are compared with available experimental data.     

Study of the Β decay of6He with allowance for second-class currents and the antineutrino mass

The effects of the rest mass of the electron antineutrino are studied with allowance for the induced tensor form-factor F_c of the second-class current according to the Weinberg classification during the decay of the⁶He nucleus. We calculate the contribution of m and F_c to the electron-antineutron angular correlation coefficient A_e and the degree of longitudinal polarization P_e of the decay electrons. When m is nonzero, the coefficient A_e tends asymptotically to zero both at the beginning and endpoint of the spectrum, whether or not the second-class currents are taken into account. The series of qualitatively new experiments planned for the near future to measure the e- correlation for pure Gamow-Teller transitions (the⁶He nucleus could be a suitable nucleus here) with an accuracy of the order of 1% would allow the available estimate of the form-factor F_c to be improved substantially.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 62–67. September, 1989.     

Study of the Δ isobar excitation in nuclei with the (3He,t) reaction

Data for the Δ excitation by the (³He,t) reaction at 2.0 GeV on various nuclei are presented together with results on ¹²C at 1.5 and 2.3 GeV. The Δ peak position and width are found to be target mass independent. Comparison with the p(³He,t) Δ⁺⁺ reaction, however, shows a shift of the position in energy of the Δ peak. Implications of these results are discussed.     

Half-lives and fine structure for the α decay of deformed even-even nuclei

The α-decay properties of well-deformed even-even nuclei are systematically calculated within the multichannel cluster model (MCCM). Instead of working in the WKB framework, the quasibound solution to the coupled Schro¨dinger equation is presented with outgoing wave boundary conditions, and the coupling potential is taken into full account in terms of the general quantum theories. The calculated α-decay half-lives are found to agree well with the experimental data with a mean factor of less than 2. The fine...     

Elastic and inelastic scattering of π mesons on 7Li nuclei

Within the diffraction theory of multiple scattering, the differential cross sections for elastic and inelastic pion scattering on a ⁷Li nucleus are calculated for the case where the final nucleus is either in the ground or in the first excited state. The nuclear wave function is set to that in the αt cluster model. The sensitivity of the calculated observables to variations in the type of the wave functions for the alpha-particle and the triton cluster and for their relative motion is investigated. Various multiplicities of scattering and rescattering on the clusters constituting the ⁷Li nucleus are taken into account, and their contributions to the cross section are revealed. The results of the calculations are compared with experimental data at E _π=143, 164, and 194 MeV.     

ΛΛ 6 He and Λ 9 Be systems in the three-body cluster model treated on the basis of differential Faddeev equations

The _ΛΛ ⁶ He and _Λ ⁹ Be hypernuclei are treated as the S=0, T=0 (for the former) and S=1/2, T=0 (for the latter) bound states of the three-cluster systems ΛΛα and Λαα, respectively. The cluster-reduction method is used to solve the s-wave differential Faddeev equations for these systems. On the basis of the MT I–III model, the ΛΛ interaction potential is specified in the form $V_{\Lambda \Lambda } = \frac{2}{3}V_{NN} $ . Phenomenological potentials are used to describe Λα and αα interactions. The binding energies of the _ΛΛ ⁶ He and _Λ ⁹ Be hypernuclei and the parameters of low-energy Λ-hyperon and α-particle scattering on a _Λ ⁵ He hypernucleus are calculated. It is shown that the proposed ΛΛ interaction potential makes it possible to reproduce faithfully the binding energy of the _ΛΛ ⁶ He hypernucleus and that scattering in the Λ _Λ ⁵ He system is similar to neutron scattering on a deuteron.     

Cross sections of the interactions of4He nuclei with protons at 8·6 and 13·6 GeV/c

⁴He-p collisions at two values of⁴He momenta-8·6 GeV/c and 13·6 GeV/c — have been studied using the one-metre JINR hydrogen bubble chamber. Total, elastic and topological cross sections have been measured. The results are in agreement with other published data. The elastic differential cross section was compared with the predictions of the Glauber model formalism.Dedicated to Academician Václav Votruba on ths occasion of his eightieth birthday.We would like to thank Mrs. M. Stehlíková for drawing the figures.     

A potential description of α-particle elastic scattering by the 6Li and 7Li nuclei

The results of analytic and numerical calculations of the real part of the ??⁶Li interaction potential in the cluster folding model are reported. Elastic scattering phases in the ??+^6,7Li systems are calculated and constructed, a classification of multipole transitions for back photodisintegration reactions is given.     

Theoretical Study of the 4He(γ, p)3H and 4He(γ, n)3He Reactions

Ab initio calculation of the total cross section for the reactions ⁴He(γ, p)³H and ⁴He(γ, n)³He is presented, using state-of-the-art nuclear forces. The Lorentz integral transform (LIT) method is applied, which allows exact treatment of the final state interaction (FSI). The dynamic equations are solved using the effective interaction hyperspherical harmonics method. In this calculation of the cross sections the three-nucleon force is fully taken into account, except in the source term of the LIT equation for the FSI transition matrix element.     

Cross sections and asymmetries for elastic π3He scattering in the energy region around the Δ resonance

For a polarized target, π³He interaction is studied in the fixed-center approximation with all rescatterings included. Only the P ₃₃ wave is taken for the πN interaction. The nuclear wave function is taken either as a sum of Gaussian functions or as a Faddeev wave function in the s-wave approximation. The differential cross sections and asymmetries for elastic π⁺³He scattering at the laboratory energies of T _π, 180, and 256 MeV are calculated. The results are compared with experimental data.     

1 GeV proton elastic scattering on 9Be nuclei in the α-cluster model with dispersion

The polarization observables for the elastic p- ⁹Be scattering at 1GeV are calculated on the basis of the multiple-diffraction scattering theory and the -cluster model with dispersion. The ⁹Be nucleus is considered as composed of two -clusters and a neutron arranged at the vertices of an isosceles triangle. The results obtained are in agreement with existing experimental data.     

Electronic structure, optical properties and lattice dynamics of MgSO3·6H2O

The electronic band structure, optical properties and lattice vibrations of MgSO(3)·6H(2)O were studied within density functional theory and compared to the experimental optical data and polarized Raman spectra. Due to the 'molecular' nature of the MgSO(3)·6H(2)O crystal all Γ-point phonon modes could be separated into groups belonging to specific structural blocks: Mg(H(2)O)(6) octahedra, SO(3) units and H(2)O molecules. All Raman lines in the experimental spectra are assigned to definite vibrations of the structure and reasonable agreement is found between theoretical and experimental mode frequencies. The temperature-dependent Raman spectra reveal at 60 °C a sharp transition from MgSO(3)·6H(2)O to anhydrous amorphous MgSO(3) without the noticeable presence of intermediate lower hydrates, such as MgSO(3)·3H(2)O.     

Determination of the nuclear vertex constants for the 7Be ↔ 3He4He vertex using theN/D equations and calculation of the astrophysical S factor for the 4He(3He, γ)7Be reaction

N/D equations taking into account the Coulomb interaction effects are used to consider the phase analysis data on ³He⁴He scattering and determine the nuclear vertex constants for the ⁷Be ? ³He⁴He vertex, where the beryllium nucleus is in the ground (3/2^?) or first excited (1/2^?) states. Information about the asymptotic normalization coefficients of the wave functions of the ⁷Be nucleus in the noted states is derived. The data obtained are used to calculate the astrophysical S factor for the ⁴He(³He, γ)⁷Be reaction.     

Study of the structure of FeSiF6·6H2O by EPR and optical spectra

The method for determining the crystalline structure from relevant EPR zero-field splitting and optical spectra data is applied to ferrous fluosilicate (FeSiF₆·6H₂O. The results, consistent with data from Mossbauer and IR magnetic resonance, show that the effective symmetry of the Fe₂₊ site in FeSiF₆·6H₂O is a rhombic distortion rather than a trigonal one (D_3d).     

Influence of D-state in 4He on S Factor for the 2H（d, γ）^4He Reaction

We employ a direct capture method to study the influence of D-state in ^4He on S factor for the ^2H（d,γ）^4He reaction, in which the D-state component of the colliding deuterons and D-state component in ^4He ground state are considered. The parameters of Woods-Saxon （WS） potentials are obtained by reproducing the binding energy of d-d （i.e. ^2H-^2H） system, and d-d elastic scattering phase shifts calculated by the resonating group method. The theoretical results are in good agreement with the experimental data at Ec.m〈 3 MeV. The impact of the D state probability in ^4He on the extrapolated value of the astrophysical S factor for ^2H（d, γ）^4He reaction is discussed.     

Analysis of the threshold anomaly in proton elastic scattering on A ∼- 30 mass nuclei

The threshold anomaly in energy-averaged excitation functions of proton elastic scattering on A ∼- 30 mass nuclei is analyzed in the framework of the Lane model for p-wave threshold effects. A quantitative correlation between the strength of the threshold anomaly and the 2p-wave neutron strength function is reported.