International Journal of Modern Physics E

In this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. More specifically, Sec. 2 discusses mass of ${\pi }^0$ in the linear sigma model coupled to quarks at zero temperature. In Sec. 7, one-loop calculation of the anisotropic pressure are discussed in the presence of strong magnetic field. In Sec. 9, chiral transition and chiral susceptibility in the NJL model is discussed for a chirally imbalanced plasma in the presence of magnetic field using a Wigner function approach. Sections 10 discusses electrical conductivity and Hall conductivity of hot and dense hadron gas within Boltzmann approach and Sec. 11 deals with electrical resistivity of quark matter in presence of magnetic field. There are several unanswered questions about the QCD phase diagram. Sections 3, 11 and 18 discuss various aspects of the QCD phase diagram and phase transitions. Recent years have witnessed interesting developments in foundational aspects of hydrodynamics and their application to heavy-ion collisions. Sections 12 and 15–17 of this article probe some aspects of this exciting field. In Sec. 12, analytical solutions of viscous Landau hydrodynamics in 1+1D are discussed. Section 15 deals with derivation of hydrodynamics from effective covariant kinetic theory. Sections 16 and 17 discuss hydrodynamics with spin and analytical hydrodynamic attractors, respectively. Transport coefficients together with their temperature- and density-dependence are essential inputs in hydrodynamical calculations. Sections 5, 8 and 14 deal with calculation/estimation of various transport coefficients (shear and bulk viscosity, thermal conductivity, relaxation times, etc.) of quark matter and hadronic matter. Sections 4, 6 and 13 deal with interesting new developments in the field. Section 4 discusses color dipole gluon distribution function at small transverse momentum in the form of a series of Bells polynomials. Section 6 discusses the properties of Higgs boson in the quark–gluon plasma using Higgs–quark interaction and calculate the Higgs decays into quark and anti-quark, which shows a dominant on-shell contribution in the bottom-quark channel. Section 13 discusses modification of coalescence model to incorporate viscous corrections and application of this model to study hadron production from a dissipative quark–gluon plasma.

Study of the characteristic properties of charged particle production in hadron–nucleus collisions at high energies by utilizing the approaches from different statistical models is performed. Predictions from different approaches using the negative binomial distribution, shifted Gompertz distribution, Weibull distribution and the Krasznovszky–Wagner distribution are considered for a comparative study of the relative success of these models. These distributions derived from a variety of functional forms are based on either phenomenological parameterizations or some model of the underlying dynamics. Some of these have also been used to study the data at the Large Hadron Collider (LHC) for both proton–proton and nucleus–nucleus collisions. Various physical and derived observables have been used for the analysis.

Shell corrections to the moment of inertia (MI) are calculated for a Woods–Saxon potential of spheroidal shape and at different deformations. This model potential is chosen to have a large depth and a small surface diffuseness which makes it resemble the analytically solved spheroidal cavity in the semiclassical approximation. For the consistent statistical-equilibrium collective rotations under consideration here, the MI is obtained within the cranking model in an approach which goes beyond the quantum perturbation approximation based on the nonperturbative energy spectrum, and is therefore applicable to much higher angular momenta. For the calculation of the MI shell corrections $\delta \mathrm{\Theta }$, the Strutinsky smoothing procedure is used to obtain the average occupation numbers of the particle density generated by the resolution of the Woods–Saxon eigenvalue problem. One finds that the major-shell structure of $\delta \mathrm{\Theta }$, as determined in the adiabatic approximation, is rooted, for large as well as for small surface deformations, in the same inhomogenuity of the distribution of single-particle states near the Fermi surface as the energy shell corrections $\delta E$. This fundamental property is in agreement with the semiclassical results $\delta \mathrm{\Theta }\propto \delta E$ obtained analytically within the non perturbative periodic orbit theory for any potential well, in particular for the spheroidal cavity, and for any deformation, even for large deformations where bifurcations of the equatorial orbits play a substantial role. Since the adiabatic approximation, $\omega \ll \mathrm{\Omega }$, with $\hslash \mathrm{\Omega }$ the distance between major nuclear shells, is easily obeyed even for large angular momenta typical for high-spin physics at large particle numbers, our model approach seems to represent a tool that could, indeed, be very useful for the description of such nuclear systems.

The location of the neutron drip line, currently known for only the lightest elements, remains a fundamental question in nuclear physics. Its description is a challenge for microscopic nuclear energy density functionals, as it must take into account in a realistic way not only the nuclear potential, but also pairing correlations, deformation effects and coupling to the continuum. The recently developed deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) includes all three aforementioned effects in the description of nuclei throughout the nuclear chart. Here, the DRHBc with the successful density functional PC-PK1 is used to investigate whether and how deformation influences the prediction for the neutron drip-line location for even–even nuclei with $8\le Z\le 20$, where many isotopes are predicted deformed. The results are compared with those based on the spherical relativistic continuum Hartree–Bogoliubov (RCHB) theory and discussed in terms of shape evolution and the variational principle. It is found that the Ne and Ar drip-line nuclei are different after the deformation effect is included. The direction of the change is not necessarily towards an extended drip line, but rather depends on the evolution of the degree of deformation towards the drip line. Deformation effects as well as pairing and continuum effects treated in a consistent way can affect critically the theoretical description of the neutron drip-line location.

Relying on previous results, that link entanglement entropy and parton distribution functions in deep inelastic scattering, and focusing on the small Bjorken scaling region we present here indications that gluon shadowing might indeed be explained as due to a depletion of the entanglement entropy, between observed and unobserved degrees of freedom, per nucleon within a nucleus, with respect to the free nucleon. We apply to gluon shadowing the general Page approach to the calculation of the entanglement entropy in bipartite systems, giving physical motivations of the results.

We try to give a comparison of the calculated Gamow–Teller $\beta$-decay half-lives for ${}^{43}\mathrm{\text{K}}$, ${}^{47}\mathrm{\text{Ca}}$ and ${}^{85}\mathrm{\text{Sr}}$ nuclei with the experimental ones obtained from ($\gamma$,p), ($\gamma$,n) and (n,$\gamma$) reactions, respectively. The calculations are performed within the framework of quasi-particle phonon nuclear model. The nucleon–nucleon interaction potential is included according to Pyatov’s restoration method. The calculated decay half-lives are also compared with available experimental data in the literature.

For the first time, a systematic study of identical superdeformed (SD) bands in $A\sim 150,130$ mass region is made, where $\mathrm{\Delta }I=4$ bifurcation is present. Four pairs of identical SD bands viz. ${\{}^{149}\mathrm{\text{Gd}}(1){,}^{148}\mathrm{\text{Gd}}(6)\}$ and ${\{}^{149}\mathrm{\text{Gd}}(1){,}^{148}\mathrm{\text{Eu}}(1)\}$ of $A\sim 150$ mass region and ${\{}^{132}\mathrm{\text{Ce}}(1){,}^{133}\mathrm{\text{Ce}}(1)\}$ and ${\{}^{133}\mathrm{\text{Ce}}(2){,}^{136}\mathrm{\text{Nd}}(1)\}$ of $A\sim 130$ mass region have been systematically studied. The present systematic study provides the universal description of the identical SD bands in various mass regions. We presented the empirical evidence of a similar structure of identical SD bands in various mass regions. For this purpose, we have used various rotational energy formulae. The free parameters are extracted from four identical SD bands. The $\mathrm{\Delta }I=4$ bifurcation in identical SD bands is calculated from shape fluctuation formulae. For the first time, this shape fluctuation model is employed to calculate the $\mathrm{\Delta }I=4$ bifurcation, making it an alternate powerful tool to study SD bands of various mass regions.

The alpha decay half-lives of actinides within modified generalized liquid drop model (MGLDM) are investigated by the Wentzel–Kramers–Brillouin (WKB) barrier penetration probability. The potential barrier was studied taking in to account of nuclear proximity, coulomb interaction and centrifugal potential with the inclusion of angular momentum. This work predicts the alpha decay half-lives of unknown actinide nuclei such as ${}^{248}$Am, ${}^{235,237,252}$Cm, ${}^{248,252,253}$Bk, ${}^{247}$Es and ${}^{248}$No. The calculated alpha decay half-lives reproduce accurately the experimental data. The predictions provided for the alpha decay half-lives within the MGLDM may be helpful for identifying the new isotopes in this field.