International Journal of Modern Physics E

The elliptic flow in collisions of neutron-rich heavy-ion systems at intermediate energies emerges as an observable sensitive to the strength of the symmetry energy at supra-saturation densities. First results obtained by comparing ratios or differences of neutron and hydrogen flows with predictions of transport models favor a moderately soft to linear density dependence, consistent with ab initio nuclear-matter theories. Comprehensive data sets of high accuracy can be expected to improve our knowledge of the equation of state of asymmetric nuclear matter.

We have studied the effects of nuclear induced breakup channel coupling on the fusion cross-section for ⁶Li+¹²C and ⁶He+¹²C systems in the near barrier energy regime using the dynamic polarization potential (DPP) approach. It has been found that there is enhancement in the fusion cross-section with respect to standard one-dimensional barrier penetration model in the below barrier energy regime while at energies above the barrier there is suppression of fusion cross-section with respect to simple barrier penetration model is observed. The agreement between data and predictions for ⁶Li+¹²C system improves significantly as a result of the inclusion of nuclear induced DPP.

The NL-RA1 effective interaction of the relativistic mean field theory is employed to study the structure of deformed and superheavy nuclei, using an axially deformed harmonic oscillator basis. It is found that a fair agreement with the experimental data is obtained for the binding energies (BE), deformation parameters and charge radii. Comparison with NL-Z2, NLSH and NL3 interactions show that NL-Z2 gives good binding but larger radii, while NL-SH gives good radii but larger binding. The NL-RA1 interaction is also tested for the new deformed superheavy element with Z≥98. Excellent agreement with the experimental binding is obtained, where the relative error in BEs of Cf, Fm, No, Rf, Sg and Ea (Z = 110) isotopes are found to be of the order ~0.1%. The NL3 predicted larger binding and larger relative errors ~0.2–0.5%. Furthermore, the experimental Q-values of the alpha-decay of the superheavy elements ²⁷⁰110, ²⁸⁸114 and ²⁹²116 are satisfactory reproduced by NL-RA1 interaction, where the agreement is much better than that predicted by the phenomenological mass FRDM model. Furthermore, the alpha-decay chain of element ²⁹⁴118 are also better reproduced by NL-RA1 interaction.

The models of the transition in medium and nuclei based on the diagram technique for direct reactions, potential description of -medium interaction and field-theoretical approach are considered. It is shown that for the transition in medium field-theoretical approach should be used. The lower limit on the free-space oscillation time τ is in the range: 10¹⁶yr>τ>1.2⋅10⁹s.

The masses of the ground state heavy baryons are studied using the hypercentral approach. The considered potential is a combination of Coulombic, linear confining and harmonic oscillator terms. An improved form of the hyperfine interaction and isospin dependent quark potential is introduced. By solving the Schrödinger equation for three particles system, we calculate the ground state masses of the baryons containing one, two and three heavy quarks. The obtained results are very close to the ones obtained in experiments or in the other works.

The relativistic six-quark equations are constructed in the framework of the dispersion relation technique. The relativistic six-quark amplitudes of dibaryons including the light u, d and heavy c, b quarks are calculated. The approximate solutions of these equations using the method based on the extraction of leading singularities of the heavy hexaquark amplitudes are obtained. The poles of these amplitudes determine the masses of charmed and bottom dibaryons with the isospins I = 0, 1, 2 and the spin-parities J^P = 0⁺, 1⁺, 2⁺.

Excitation functions for the reactions ¹⁹⁷Au(p,n)^197gHg and ¹⁹⁷Au(p,n)^197mHg have been measured over the energy ranges from threshold up to 20 MeV using stacked foil activation technique. The isomeric cross-section ratio σ_m/(σ_m+σ_g) for the formation of ^{197g, m}Hg was determined. The excitation functions and isomeric cross-section ratios were calculated for the reactions ¹⁹⁷Au(p,n)^197g,mHg, ¹⁹⁷ Au(p,2n)¹⁹⁶Hg, ¹⁹⁷Au(p,3n)^195g,mHg, ¹⁹⁷Au(p,4n)¹⁹⁴Hg, ¹⁹⁷ Au(p,5n)^193g,mHg, ¹⁹⁷Au(α, n)²⁰⁰Tl, ¹⁹⁷Au(α,2n)¹⁹⁹Tl, ¹⁹⁷Au(α,3n)^198g,mTl, ¹⁹⁷Au(α,4n)¹⁹⁷Tl and ¹⁹⁷Au(α,5n)^196g,mTl from reaction threshold up to 40 MeV for proton induced reactions and 80 MeV for alpha induced reactions. The results were compared with the theoretical cross-sections calculated by means of the code EMPIRE-II and with the available literature data, which makes use of the Hauser Feshbach model for the compound nuclear calculations and the exciton model for the pre-equilibrium emission part. The isomeric cross-section ratio is found to depend strongly on the relative spins of the isomeric and ground state, energy difference between the levels, presence of intermediate states and some dependence on decay modes and on the onset of pre-equilibrium emission.

We investigated the analytical -wave solutions of Dirac equation for trigonometric Pöschl–Teller (PT) potential under the pseudospin symmetry condition. The energy eigenvalues equation and corresponding wave functions are obtained by using the Nikiforov–Uvarov (NU) method. The energy bound states are also calculated numerically.

The extended quark sigma model, which includes higher-order mesonic interactions is applied at finite temperature. The field equations are solved using the mean-field approximation. Nucleon properties such as the nucleon mass, the magnetic moments of the proton and neutron, and the pion-nucleon coupling constant are examined as functions of temperature. The obtained results indicate that the deconfinement phase transition conditions are satisfied in the present work at higher values of temperature. A comparison with other models is presented.

The shell and pairing correction energies are calculated for heavy and superheavy nuclei (SHN) by means of the Strutinsky's method. The single-particle (s.p.) energy levels are obtained from the diagonalization of the Woods–Saxon s.p. Hamiltonian in the deformed harmonic oscillator basis for both neutrons and protons. The residual pairing interaction is calculated by means of the usual Bardeen–Cooper–Schrieffer (BCS) approximation. A two-dimensional deformation space describing axially and reflection-symmetric shapes of nuclei has been used. Based on the shell and pairing correction energies, the signatures of the magic numbers appear at the spherical shell closures Z = 82, 114, 164 and N = 126, 184, 228 and 308. There are also signatures for some other shell closures at, e.g., Z = 108 and N = 162 which appear only when the deformation degrees of freedom is taken into account.

The ρ-meson spectral function in hot nuclear matter is studied by taking into account the pion and the nucleon loops within the quantum hadrodynamics (QHD) model as well as using an effective chiral SU(3) model. The effects of density and temperature on the spectral function of the ρ-meson are studied assuming the ρ-meson to be with a finite momentum. These investigations are performed using both the mean field approximation (MFA) and the relativistic Hartree (RHA) approximation. The inclusion of the nucleon loop is observed to considerably change the ρ-meson spectral function. Due to a larger mass drop of ρ-meson in the RHA, it is seen that the spectral function shifts towards the low invariant mass region, whereas in the MFA the spectral function is seen to be almost centered around the nominal ρ-pole, but develops a second peak due to the opening of the Nh-channel. Within both the Walecka and the chiral SU(3) models, it is observed that the ρ-meson spectral function has a strong dependence on the nucleon-ρ meson tensor coupling.