International Journal of Modern Physics E

The reaction π⁺π^-→π⁺π^- is studied in the non-relativistic quark model with the ³P₀ quark–antiquark dynamics. The cross section of the reaction π⁺π^-→π⁺π^- is well reproduced even for rather high energies.

We study the recently discovered Θ⁺ baryon in the context of the perturbative chiral quark model. The basic configuration of the Θ⁺ is a pentaquark bound state, where the single particle wave functions are the ground state solutions of a confining potential. We classify the resulting pentaquark multiplets as the J^P=1/2^- and 3/2^- flavor SU(3) antidecuplet. The full mass spectrum of the multiplets is determined by including the meson and gluon cloud contributions, which induce flavor SU(3) breaking. The resulting 3/2^- antidecuplet is about 185 MeV heavier than the 1/2^- one, mainly because of the semi-perturbative gluon effects. We assign the observed Θ⁺ baryon as a member of the 1/2^- antidecuplet and discuss in particular its relation to the recent experimental signal for a Ξ^-- baryon.

There is experimental evidence of an increase in the temporal component of the weak axial vector current in nuclei. Most of this increase is accounted for by meson exchange currents. We consider further corrections from pions and the sigma mean-field. These corrections, however, are found to reduce the coupling, which is already insufficiently large.

The influence of the intruder level on nuclear deformation is studied within the framework of the nucleon-pair shell model, truncated to an SD-pair subspace. The results suggest that the intruder level has a tendency to reduce the deformation for nuclei in lower and middle shells, and plays an important role in determining the onset of rotational behavior.

The Ramsauer–Townsend effect in hydrogen is used in a heterogeneous solid hydrogen-deuterium-tritium (H/D/T) multi-layer system to provide forced resonance muonic deuterium-tritium molecule formation. The effects of hyperfine splitting in the μd atom on the final state of nuclear spins are studied in the μpd molecule at low temperature. As deuterium concentration increases, so does the spin-flip rate, thus reducing the initial population of the quartet (s=3/2) nuclear spin of the μpd molecule and enhancing the doublet (s=1/2) state. The doublet rate is dominant, and total fusion yield increases with deuterium concentration until the lack of protium atoms significantly reduces the rate of μpd molecule formation and μdd fusion dominates completely. The Wolfenstein–Gerstein effect and the no-quartet theorem in the solid H/D layer are considered by solving the muon dynamical equations for various deuterium concentrations. It is shown that the no-quartet theorem is not valid at low temperature and deuterium concentration, but is valid only if one neglects the mixed-symmetry components. The written coupled linear point dynamical equations for the suggested system are solved using the "Lsode" computer code. The results obtained for the optimum layer thicknesses and deuterium concentration are compared with the results of a solid homogeneous deuterium-tritium system in the same physical condition (temperature, density and deuterium concentration). It is shown that for the same physical conditions, the muon cycling coefficient of two isotopes of deuterium-tritium (D/T) has only 2.7% of the muon cycling coefficient of the suggested forced solid heterogeneous H/D/T fusion system. It is shown that with very little deuterium concentration (c_d=0.005), the obtained muon cycling rate and coefficient are ~147 μs^-1 and 178, respectively.

We present the Coulomb-modified eikonal model formalism based on a hyperbolic trajectory by using a tangential velocity at the distance of closest approach. By assuming that ¹¹Li has a halo structure of two weakly bound neutrons around the ⁹Li core, we take the total nuclear optical potential as a sum of the core and the two halo neutrons. The theoretical calculations for the elastic scattering of ⁹Li+p and ¹¹Li+p at E_lab/A=60 and 62 MeV, respectively are in good agreements with the observed data. It is found that the break-up effect of halo neutrons and the tangential velocity at the distance of closest approach are both important to understand the elastic cross sections of ¹¹Li+p system at E_lab/A=62 MeV.

We measure the energy spectra of α-particles and protons in ²⁸Si+^natSi and ²⁸Si+²⁷Al reactions at 4–5 MeV/A for both forward and backward angles. We show with a statistical model that the choice of the level density parameter plays a very crucial role in explainning the evaporation spectra. The shell corrected Gilbert Cameron level density parameter is found to give satisfactory results.

We obtained a nonrelativistic deuteron wave function that accounts for the D-state and has correct asymptotic behavior. This was achieved on the basis of the experimentally measured charge and quadrupole deuteron form factors. The differential cross section of the elastic deuteron-nucleus scattering has been calculated by using this wave function. These predictions agree with the experimental data at the energy of 110 MeV. The integrated cross sections of the various processes involving the deuteron-nucleus interactions were also calculated.

We will study fermionic systems like atomic nuclei and bosonic systems like the correlated atoms in a trap from an information-theoretical point of view. The Shannon and Onicescu information measures are calculated for the above systems by comparing the correlated and uncorrelated cases as functions of the strength of the short range correlations. One-body and two-body density and momentum distributions are employed. Thus, the effect of short-range correlations on the information content is evaluated. The magnitude of distinguishability between the correlated and uncorrelated densities is also discussed employing suitable measures for the distance of states i.e. the well known Kullback–Leibler relative entropy and the recently proposed Jensen–Shannon divergence entropy. We will see that the same information-theoretical properties hold for quantum many-body systems obeying Bose–Einstein and Fermi–Dirac (statistics).

By considering common positions, by distinguishing their features and properties, by their globalization, by using a unified approach of description and a unified method of calculation, we study the various non-equilibrium processes, which appeared as a results of transportation of nuclear particles in various finite open nuclear-physics systems. We interpret the forming and the decay of new qualitative structures under exceeding limiting values of parameter, which characterizes the system. We also interpret the effects of bifurcation of solutions and changes of topological characteristics of condensed mediums over a long period of time.