International Journal of Modern Physics E

In relativistic heavy-ion collisions, a highly occupied gluonic matter is created shortly after initial impact, which is in a nonthermal state and often referred to as the Glasma. Successful phenomenology suggests that the glasma evolves rather quickly toward the thermal quark–gluon plasma (QGP) and a hydrodynamic behavior emerges at a very early time ~ô(1) fm/c. Exactly how such "apparent thermalization" occurs and connects the initial conditions to the hydrodynamic onset, remains a significant challenge for theory as well as phenomenology. We briefly review various ideas and recent progress in understanding the approach of the glasma to the thermalized QGP, with an emphasis on the kinetic theory description for the evolution of such far-from-equilibrium and highly overpopulated, thus weakly-coupled yet strongly interacting glasma.

Thomas' approximation to the general R-matrix theory of Wigner and Eisenbud is used to study the development of fluctuations in the cross-section for inelastic neutron scattering, to a definite state, in the transition from the resonance region to the continuum. In standard analyses of Ericson fluctuations, averaging of all resonance parameters is carried out from the beginning. Here, no averaging is performed; it is therefore possible to study, in detail, the effects of variations in both the random distributions of the phases of interfering amplitudes associated with elastic and inelastic scattering and the statistical distributions of parameters of the underlying resonances. The present microscopic model is not limited to the study of nuclear reactions; studies of inelastic scattering associated with quantum dots in semiconductors at low temperature and electron–atom interactions that involve many overlapping resonances, require analyses of the kind reported.

The total nuclear reaction cross-section σ_R for p-⁴He in the energy range from 25 MeV to 1000 MeV is calculated within Glauber and Coulomb-modified Glauber models. The Coulomb-modified Glauber model (CMGM) is introduced via modification of the Coulomb trajectory of the projectile from a straight line, and calculation of the effective radius of interaction. The effects of in-medium nucleon–nucleon (NN) total cross-section, phase variation, high order momentum transfer component of nucleon–nucleon elastic scattering amplitude and Pauli blocking are studied. It is pointed out that the phase variation of the nucleon–nucleon amplitude plays a significant role in describing σ_R with γ = -1.6 fm² at in-medium nuclear density ϱ = 0 and γ = -2 fm² at ϱ = 0.17 fm^-3 in the whole energy range. A remarkable fit to the available experimental data is obtained by invoking Pauli blocking and high order momentum transfer of nucleon–nucleon (NN) elastic scattering amplitude for E_p < 100 MeV.

The relativistic six-quark equations for the molecule NΞ are found in the dispersion relation technique. The relativistic six-quark amplitudes of the hexaquark including the quarks of three flavors (u, d, s) are calculated. The pole of these amplitudes determines the mass of NΞ state M = 2252 MeV. The binding energy is equal to 3 MeV.

A systematic study of rapidity dispersion parameter as a quantitative measure of clustering of particles has been carried out in the interactions of ¹⁶O, ²⁸Si and ³²S projectiles at 4.5 A GeV/c with heavy (AgBr) and light (CNO) groups of targets present in the nuclear emulsion. For all the interactions, the total ensemble of events has been divided into four overlapping multiplicity classes depending on the number of shower particles. For all the interactions and for each multiplicity class, the rapidity dispersion parameter values indicate the occurrence of clusterization during the multiparticle production at Dubna energy. The measured rapidity dispersion parameter values are found to decrease with the increase of average multiplicity for all the interactions. The dependence of rapidity dispersion parameter on the average multiplicity can be successfully described by a relation D(η) = a + b〈n_s〉 + c〈n_s〉². The experimental results have been compared with the results obtained from the analysis of Monte Carlo simulated (MC-RAND) events. MC-RAND events show weaker clusterization among the pions in comparison to the experimental data.

We investigate the properties of strangelets at zero temperature with a new quark model in which the linear confinement and one-gluon-exchange (OGE) interactions are integrated as a whole. The charge, parameters dependence and the stability of strangelets are discussed. Our results showed that the OGE interaction lowers the energy of a strangelet, and consequently makes its stable radius smaller than that in the case of not including this interaction, and less than that of a nucleus with the same baryon number. Therefore, the strangelet in the present model has more chance to be absolutely stable.

We study the effects of adding a sterile neutrino to three active neutrinos (3 + 1 scheme) in the calculation of primordial abundances. Taking the normalization constant (a) of the occupation factor of the sterile neutrino and the active-sterile mixing angle (ϕ) as free parameters, we calculate the neutrino distribution function and primordial abundances of light nuclei. We set constrains on these parameters by using the available data on the abundances of D, ⁴He and ⁷Li. Results are consistent with small values of a and ϕ. The extracted value of the baryon-to-photon ratio (η_B), which is constrained by the Wilkinson Microwave Anisotropy Probe (WMAP) value , and Planck observations, depends strongly on the inclusion of the lithium data in the fit.

The entropy excess of ¹⁶³Dy compared to ¹⁶²Dy as a function of nuclear temperature have been investigated using the mean value Bardeen–Cooper–Schrieffer (BCS) method based on application of the isothermal probability distribution function to take into account the statistical fluctuations. Then, the spin cut-off excess ratio (moment of inertia excess ratio) introduced by Razavi [Phys. Rev. C88 (2013) 014316] for proton and neutron system have been obtained and are compared with their corresponding data on the BCS model. The results show that the overall agreement between the BCS model and mean value BCS method is satisfactory and the mean value BCS model reduces fluctuations and washes out singularities. However, the expected constant value in the entropy excess is not reproduced by the mean value BCS method.

This paper presents the results of an investigation pertaining to multifractal structure, degree of multifractality and occurrence of deconfinement phase transition. These results are obtained by carrying out analysis of generalized dimensions and Levy index involving relativistic charged particles produced on 14.5A GeV/c²⁸Si-nucleus collisions following Takagi's approach. The values of Levy index, μ, generalized fractal dimensions, D_q and degree of multifractality, β_q, for different orders of moments are calculated in terms of Takagi moments for the experimental, FRITIOF, HIJING and random Monte Carlo (MC-RAND) generated events. The values of multifractal specific heats for all the above data sets are extracted using generalized dimensions, D_q. The analysis also shows small variations in the degree of multifractality for the experimental, FRITIOF and HIJING simulated events. However, the degree of multifractality is quite larger for the random Monte Carlo ²⁸Si-nucleus generated events at 14.5A GeV/c. Furthermore, the analyses of multifractal specific heat and Levy index in terms of Takagi moments support the presence of multifractality and occurrence of deconfinement phase transition in the experimental and simulated data sets, but for the uncorrelated Monte Carlo simulated events, occurrence of nonthermal phase transition is revealed.

This paper refers to another attempt to search for spherical double shell closure nuclei beyond Z = 82, N = 126. All calculations and results are based on a newly developed approach entitled as simple effective interaction (SEI). Our results predict that the combination of magic nucleus occurs at N = 182 (Z = 114, 120, 126). All possible evidences for the occurrence of magic nuclei are discussed systematically. And, the obtained results for all observables are compared with the relativistic mean field theory for NL3 parameter.

Empirical relations for the preformation probability of cluster decay process in terms of the Q-value, mass asymmetry (η), mass number of the emitted cluster A₂ is analyzed based on the discrepancy between the calculated and experimental half-lives of the cluster emitters. For the different empirical expressions considered corresponding to different physical quantities the preformation probability for the complete binary breakup of ²²⁶Ra is calculated and the obtained results are compared with the preformed cluster model calculation (P₀(PCM)) and another calculation in which the overlapping penetration probability is treated as the preformation probability (P₀(μ)). Our empirical results for the use of Q-value compare well with P₀(μ). Results due to the use of Q and its powers along with the combination of mass number A₂ of the cluster emitted, and mass asymmetry η, reveal that preformation factor depends strongly on Q-value rather than A₂ and η. Calculated half-lives of different cluster decays for the use of empirical P₀ values are found to be in good agreement with the experimental values.