International Journal of Modern Physics E

Correlations between production of charged pions and formation of light nuclei in collisions of oxygen nuclei with protons at $3.25A$GeV/$c$ were investigated. It was deduced that the mechanisms of formation of light fragments with $A=\mathrm{2–4}$ and the processes of generation of charged pions do not depend on each other.

The properties of dense quark matter are investigated in the perturbation theory with a rapidly convergent matching-invariant running coupling. The fast convergence is mainly due to the resummation of an infinite number of known logarithmic terms in a compact form. The only parameter in this model, the ratio of the renormalization subtraction point to the chemical potential, is restricted to be about 2.64 according to the Witten–Bodmer conjecture, which gives the maximum mass and the biggest radius of quark stars to be, respectively, two times the solar mass and 11.7km.

In previous works, we examined the spectra for systems of two protons and two neutrons, in a single $j$ shell calculation, by obtaining matrix elements from experiment. More recently, we considered the schematic interactions in the same model space. We continue in this vein here. The present work and the former can be regarded as two bookends on a bookshelf.

In this paper, the interacting boson–fermion model generalized by considering an np-boson and the single nucleon as a vector coupled in isospin to the bosons to form the model isospin invariant. The transitional interacting boson–fermion model Hamiltonians in IBFM-1 and IBFM-3 versions based on affine SU(1,1) Lie algebra are employed to describe the evolution from the spherical to deformed gamma unstable shapes along the chain of Cu isotopes. We have studied the energy spectra of ${}^{61-69}\mathrm{\text{Cu}}$ isotopes and B(E2) transition probabilities of ${}^{61-69}\mathrm{\text{Cu}}$ isotopes in the shape phase transition region between the spherical and gamma unstable deformed shapes. Good agreement was achieved between the calculated results using the models and measured data. The results obtained and the values of control parameters used in this calculation indicated that the odd-mass Cu isotopes located near the closed shell provided good examples of ${\mathrm{\text{Spin}}}^{\mathrm{\text{BF}}}$(5) symmetry without any significant deformed gamma-unstable structure. Some comparisons are made with IBFM-1.

The complete spectrum of $c\bar{b}$ states is obtained in a phenomenological nonrelativistic quark model (NRQM), which consists of a confinement potential and one gluon exchange potential (OGEP) as effective quark–antiquark potential with coupled channel effects. We make predictions for the radiative decay (E1 and M1) widths and weak decay widths of $c\bar{b}$ states in the framework of NRQM formalism.

The equation of state (EOS) of nuclear matter is investigated in a semi-classical mean-field (MF) approach. Starting from the phase-space NN-interaction of Myers and Swiatecki [Nucl. Phys. A 601 (1996) 141], the EOS of nuclear matter by the Thomas–Fermi approximation is derived. A self-consistent semi-classical approach is presented by employing the Landau Fermi-Liquid theory (LFT). In our statistical approach, the phase-space occupation number can be expressed in terms of an extended effective mass which is affected by both temperature and nucleonic density. Accordingly, an explicit expression of the nucleonic chemical potential inside the nucleonic occupation number can be obtained. Special attention is also devoted to the density dependence of the nuclear symmetry free energy at different temperatures. The results of this model are compared with other theoretical predictions.

The momentum distribution and the correlation due to the mass difference were studied both in the case of the conventional expectation value and in the case of $q$-expectation value, when the momentum distribution is described by a Tsallis distribution with the entropic parameter $q\ge 1$. The magnitude of the momentum distribution for hard modes increases as $q$ increases, and the $q$-dependence of the momentum distribution is quite weak for soft modes. The correlation at $q>1$ is larger than that at $q=1$ for soft modes, while the correlation at $q>1$ is smaller than that at $q=1$ for hard modes. The $q$-dependences of these quantities in the case of $q$-expectation value are weaker than those in the case of the conventional expectation value, respectively.

Some positive and negative parity energy bands of odd-A isotopes of Europium ${}^{\text{153–159}}\text{Eu}$ have been studied within the Projected Shell Model (PSM) framework. Calculated excitation energy spectra, transition energies, E2 and M1 transition probabilities, quadrupole and magnetic moments are compared with experimental data wherever available. Reasonably good agreement is obtained with the observed data.

The projected shell model (PSM) with the deformed single-particle states, generated by the standard Nilsson potential, is applied to study the negative-parity high spin states of ${}^{115\text{–}125}\text{Sb}$ nuclei. The nuclear structure quantities like band structure and back-bending in moment of inertia have been calculated with PSM method and are compared with the available experimental data. In addition, the reduced transition probabilities, i.e., B$(E2)$ and B$(M1)$, are also obtained for the yrast band of these isotopes for the first time by using PSM wave function. A multi-quasiparticle structure has been predicted for ${}^{115\text{–}125}\text{Sb}$ isotopes by the present PSM calculations.