International Journal of Modern Physics E

A noninteracting hadron resonance gas model is used often to study the hadronic phase formed in heavy ion collisions. Interaction among various hadronic constituents can be included using an S-matrix-based virial expansion approach. The virial coefficients require the dynamical information about the scattering phase shifts, which is used to compute various thermodynamic observables of an interacting hadronic gas. The attractive part of the phase shifts are calculated using K-matrix formalism while the repulsive part is obtained by fitting to experimental data. Calculation of various thermodynamic variables like pressure, energy density, specific heat capacity, etc., along with the second and higher-order correlations and fluctuations of conserved charges are done, first with only attraction and then with both attraction and repulsion included. Comparison of S-matrix results indicate a better agreement with lattice QCD data than the ideal HRG model across all thermodynamic variables.

Recent work on the particle composition (hadrochemistry) of the final state in proton–proton (p–p), proton–lead (p–Pb) and lead–lead (Pb–Pb) collisions as a function of the charged particle multiplicity ($\mathrm{\text{d}}{N}_{\mathrm{\text{ch}}}/\mathrm{\text{d}}\eta$) is reviewed. It is argued that for high multiplicities (at least about 20 charged hadrons in the mid-rapidity interval), consistent results are obtained in the thermal model.

We have attempted to review on microscopic calculation of transport coefficients like shear and bulk viscosities in the framework of hadron resonance gas (HRG) model, where a special attention is explored on the effect of finite system size. The standard expressions of transport coefficients, obtained from relaxation time approximation of kinetic theory or diagrammatic Kubo-type formalism, carry mainly two temperature-dependent components — thermodynamical phase space and relaxation time of medium constituent. Owing to the quantum effect of finite system size, thermodynamical phase space can be reduced as its momentum distribution will be started from some finite lower momentum cut-off instead of zero momentum. On the other hand, relaxation time of hadrons can also face finite size effect by considering only those relaxation scales, which are lower than the system size. Owing to these phenomenological issues, we have proposed a system size-dependent upper bound of transport coefficients for ideal HRG model, whose qualitative technique may also be applicable in other models. This finite size-prescription may guide to shorten the broad numerical band, within which earlier estimated values of transport coefficients for hadronic matter are located. It is also suspected that the hadronic matter may not be far from the (nearly) perfect fluid nature like the quark gluon plasma.

In this work, we extend our earlier study [S. Chopra, Hemdeep, A. Kaur and R. K. Gupta, Phys. Rev. C 93 (2016) 024603] of ${}^{12}\mathrm{\text{C}}+{}^{93}\mathrm{\text{Nb}}\to {}^{105}{\mathrm{\text{Ag}}}^{\ast }$ reaction at below- and near- to above-barrier energies for both coplanar (${\mathrm{\Phi }}_c=0^{\circ }$) and noncoplanar ($\mathrm{\Phi }\ne 0^{\circ }$) degrees-of-freedom. Our main aim is to see the texture of variation of compound nucleus (CN) fusion probability $P_{\mathrm{\text{CN}}}$ at all the experimentally available center-of-mass energies ($E_{c.m.}$) in the range 41–69MeV, using the dynamical cluster-decay model (DCM). In this study, we worked for both degrees-of-freedom, having compact configurations (${𝜃}_{ci}$) and including higher multipole deformations (quadrupole to hexadecapole, ${\beta }_{2i}-{\beta }_{4i}$) of nuclei. In the work of above-mentioned reference, for ${}^{105}$Ag${}^{\ast }$ (weakly fissioning nuclear system), we found a discrepancy in $P_{\mathrm{\text{CN}}}$, i.e., increasing function with increasing $E_{c.m.}$, belongs to superheavy nuclei for the case of ${\mathrm{\Phi }}_c=0^{\circ }$ [see Fig. Fig.4 of [A. Kaur, S. Chopra and R. K. Gupta, Phys. Rev. C 90 (2014) 024619], but this erroneous result moved to correct one after the inclusion of $\mathrm{\Phi }\ne 0^{\circ }$ (decreasing with increasing $E_{c.m.}$, weakly fissioning class), which encouraged us to check the trend of $P_{\mathrm{\text{CN}}}$ at all available energies. Our evaluation framework shows the noncoplanar configuration, with higher multipole deformations ${\beta }_{2i}-{\beta }_{4i}$ included, as the most probable configuration for studying the heavy-ion reactions [S. Chopra, Hemdeep, P. Kaushal and R. K. Gupta, Phys. Rev. C 98 (2018) 041603(R)]. Second, our interest is to check the consistency of experimental data, where the experimentalists have given the data with the mixing of three different experiments for same reaction. In this study, we have found that our results are in good agreement and consistent with only the latest experimental data at five $E_{c.m.}$’s (=41.097, 47.828, 54.205, 60.051 and 65.454MeV), i.e., showing large ($\sim$90%) noncompound nucleus contribution (or equivalently quasi-fission/Incomplete fusion) in the (total) fusion cross-section.

Forward recoil range distribution of evaporation residues (ERs) populated through complete fusion (CF) and incomplete fusion (ICF) dynamics in ${}^{16}$O + ${}^{124}$Sn system have been measured. Different full and partial linear momentum transfer components have been observed. The results indicate the occurrence of ICF involving break-up of ${}^{16}$O into ⁴He + ${}^{12}$C and ⁸Be + ⁸Be. However, the present data shows that the ERs are populated through both CF and ICF. A systematic study was performed which shows that the ICF fraction rises exponentially with the established entrance channel parameters and their various combinations. Moreover, these present results clearly show that $Z_P{Z}_T.{\mu }_{EC}^{AS}$ is able to explain the ICF dynamics more conclusively than combined parameter $Z_P{Z}_T.{\beta }_2$ for the systems having spherical or slightly deformed target. Further, the dependence of ICF dynamics on target structure has also been studied through a new parameter $N/Z$ of the target. The parameter $N/Z$ is directly associated with the target structure and has been found more effective and sensitive than existing parameters to investigate the target structure effect on ICF dynamics. Thus, the present observations suggest that $N/Z$ ratio of the target should also be considered as an important entrance channel parameter which strongly affects the ICF dynamics.

Conceivable Lorentz-violating effects in the neutrino sector remain a research area of great general interest, as they touch upon the very foundations on which the Standard Model and our general understanding of fundamental interactions are laid. Here, we investigate the relation of Lorentz violation in the neutrino sector in light of the fact that neutrinos and the corresponding left-handed charged leptons form $SU{(2)}_L$ doublets under the electroweak gauge group. Lorentz-violating effects thus cannot be fully separated from questions related to gauge invariance. The model dependence of the effective interaction Lagrangians used in various recent investigations is explored with a special emphasis on neutrino splitting, otherwise known as the neutrino-pair Cerenkov radiation and vacuum-pair emission (electron–positron-pair Cerenkov radiation). We highlight two scenarios in which Lorentz-violating effects do not necessarily also break electroweak gauge invariance. The first of these involves a restricted set of gauge transformations, a subgroup of $SU{(2)}_L\times U{(1)}_Y$, while in the second where differential Lorentz violation is exclusively introduced by the mixing of the neutrino flavor and mass eigenstates. Our study culminates in a model which fully preserves $SU{(2)}_L\times U{(1)}_Y$ gauge invariance, involves flavor-dependent Lorentz-breaking parameters, and still allows for Cerenkov-type decays to proceed.

Using the gluon condensation (GC) model, we predict a possible connection of the broken power phenomenon between the energy spectra of electron and proton. We find that once the GC occurs, large amount of gluons accumulate near the GC threshold. This phenomenon provides a possible source of the power rule, broken in the energy spectra of cosmic rays, and even predicts the connection between them.

In this work, we simultaneously reanalyzed the differential elastic scattering cross-sections ($d\sigma /d\mathrm{\Omega }$) and the vector analyzing power ($A_y$) of $\mathrm{\text{p}}+{}^6$He elastic scattering. This analysis was performed using the folded optical model for both real central and spin-orbit (SO) potentials, respectively. For the imaginary central, we used the usual Woods-Saxon (WS) form. Three different model density distributions are used to calculate the potential. We aimed to examine the applicability of the microscopically derived SO potential and the structure effect of ⁶He nucleus. The presence of the $A_y$ experimental data of $\mathrm{\text{p}}+{}^6$He makes it interesting for this study. Our calculations showed that the three densities gave similar predictions for the cross-sections data. The three microscopic SO potentials calculations of $A_y$ are not in a good agreement with the experimental data. We concluded that the SO formalism in its current form needs more investigations for exotic halo nuclei.

We have performed a systematic calculation on the alpha decay half-lives of heavy mass nuclei with 106 $\le Z\le$ 118, within the universal decay law (UDL) and modified universal decay law (MUDL). The calculated half-life values are found to be in agreement with the experimental data. The standard deviations of the logarithm of half-lives are found to be the least for MUDL in all cases of even–even, even–odd, odd–even and odd–odd, so the MUDL formula is better than UDL formula for alpha decay studies. We have predicted half-lives of some superheavy nuclei (SHN) in the region $Z=110$–118 that are not yet experimentally detected. The decay energies are computed using three different mass models. We hope this study will help future measurements on alpha decay half-lives of SHN.

By using the multidimensional Langevin model, including elongation, neck thickness, asymmetry parameter and orientation degree of freedom, the fission dynamics of some ${}^{16,18}$O-, ${}^{40}$Ar- and ${}^{64}$Ni-induced fusion–fission reactions were investigated. We calculated mean pre-scission neutron kinetic energy, pre-scission neutron multiplicity and fission time. Mass-split dependence of pre-scission neutron multiplicity and sensitivity of multiplicity on different value of the level density parameter for fission and neutron emission of highly excited compound nuclei were studied. One can conclude reasonable agreement between theory and tentative results for different reactions.

The elastic lepton–deuteron scattering was considered within the limits of zero lepton mass. The deuteron wave function in the coordinate representation for Reid93 potential was applied to numerical calculations. The angular-momentum dependence of values of the spin correlation coefficients $C_{xz}^{(0)}$, $C_{zz}^{(0)}$ and tensor asymmetries $A_{xx}^{(0)}$, $A_{xz}^{(0)}$, $A_{zz}^{(0)}$ were evaluated in 3D format for Reid93 potential. These polarization observables are analyzed at different energies and scattering angles. The influence of the choice of the potential model and their nodes on the calculations of the polarization observables at a fixed scattering angle was taken into account. The application of the obtained values allows better explanation and illustration of the laws for the elastic lepton–deuteron scattering.

With the recent measurement of GW170817 providing constraints on the tidal deformability (TD) of a neutron star, it is very important to understand what features of the equation of state (EoS) have the biggest effect on it. We therefore study the contribution of the crust to the TD and the moment of inertia (MoI) of a neutron star for a variety of well-known EoS. It is found that the contributions to these quantities from the low-density crust are typically quite small and as a result the determination of the TD provides an important constraint on the EoS of dense matter.

The deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) has been proved as one of the best models to probe the exotic structures in deformed nuclei. In DRHBc, the potentials and densities are expressed in terms of the multipole expansion with Legendre polynomials, the dependence on which has only been touched for light nuclei so far. In this paper, taking a light nucleus ${}^{20}$Ne and a heavy nucleus ${}^{242}$U as examples, we investigated the dependence on the multipole expansion of the potentials and densities in DRHBc. It is shown that the total energy converges well with the expansion truncation both in the absence of and presence of the pairing correlation, either in the ground state or at a constrained quadrupole deformation. It is found that to reach the same accuracy of the total energy, even to the same relative accuracy by percent, a larger truncation is required by a heavy nucleus than a light one. The dependence of the total energy on the truncation increases with deformation. By decompositions of the neutron density distribution, it is shown that a higher-order component has a smaller contribution. With the increase of deformation, the high-order components get larger, while at the same deformation, the high-order components of a heavy nucleus play a more important role than that of a light one.