Besides the yield ratio of free spectator neutrons produced in ultracentral ${}^{96}\mathrm{Zr}$+${}^{96}\mathrm{Zr}$ to ${}^{96}\mathrm{Ru}$+${}^{96}\mathrm{Ru}$ collisions [Liu et al., Phys. Lett. B 834, 137441 (2022)], we propose that the yield ratio $N_n/N_p$ of free spectator neutrons to protons in a single collision system at the BNL Relativistic Heavy Ion Collider or the CERN Large Hadron Collider can be a more sensitive probe of the neutron-skin thickness $\mathrm{\Delta }{r}_{\mathrm{np}}$ and the slope parameter $L$ of the symmetry energy. The idea is demonstrated based on the proton and neutron density distributions of colliding nuclei obtained from Skyrme-Hartree-Fock-Bogolyubov calculations, and on a Glauber model that provides information of spectator matter. The final spectator particles are produced from direct emission, clusterization by a minimum spanning tree algorithm or a Wigner function approach, and deexcitation of heavy clusters by gemini. A larger $\mathrm{\Delta }{r}_{\mathrm{np}}$ associated with a larger $L$ value increases the isospin asymmetry of spectator matter and thus leads to a larger $N_n/N_p$, especially in ultracentral collisions where the multiplicity of free nucleons are free from the uncertainties of cluster formation and deexcitation. We have further shown that the double ratio of $N_n/N_p$ in isobaric collision systems or in collisions by isotopes helps to cancel the detecting efficiency for protons. Effects from nuclear deformation and electromagnetic excitation are studied, and they are found to be subdominant compared to the expected sensitivity to $\mathrm{\Delta }{r}_{\mathrm{np}}$.

A system of bosons studied within the mean-field framework has two fascinating phenomena: a liquid-gas first order phase transition and Bose-Einstein condensation. Interplay between these two phenomena is being investigated. Depending on the mean-field potential parameters one can observe two types of critical points, called “Boltzmann” and “Bose,” that belong to different universality classes with distinct sets of critical exponents. As examples of Bose and Boltzmann CPs pion and $\alpha$ matter are considered, respectively. In general, the phase diagram can have one of the CPs or both of them.

The compound nuclei ${}^{58}\mathrm{Co}^{*}$ and ${}^{61}\mathrm{Ni}^{*}$ have been populated at overlapping excitation energies by transfer reactions ${}^{56}\mathrm{Fe}({}^6\mathrm{Li},\alpha ){}^{58}\mathrm{Co}^{*}$ (surrogate of $n+{}^{57}\mathrm{Co}$) at $E_{\mathrm{lab}}$ = 35.9 MeV and ${}^{59}\mathrm{Co}({}^6\mathrm{Li},\alpha ){}^{61}\mathrm{Ni}^{*}$ (surrogate of $n+{}^{60}\mathrm{Ni}$) at $E_{\mathrm{lab}}$ = 40.5 MeV, respectively. The ${}^{57}\mathrm{Co}(n,xp$) cross sections in the equivalent neutron energy range of 8.6–18.8 MeV have been determined within the framework of surrogate reaction ratio method using ${}^{60}\mathrm{Ni}(n,xp$) cross section values from the literature as reference. The proton decay probabilities of the compound systems have been determined by measuring evaporated protons at backward angles in coincidence with projectile-like fragments detected around the grazing angle. The measured ${}^{57}\mathrm{Co}(n,xp$) cross sections are in good agreement with both the predictions of talys-1.8 statistical model code with default parameters using different microscopic level densities and data evaluation library jeff-3.3 up to equivalent neutron energy $\approx 12.6$ MeV, while for higher energies the measured ${}^{57}\mathrm{Co}(n,xp$) cross sections are found to be consistently higher than the predictions. However, the talys-1.8 calculations with modified values of input potential parameters provide a reasonable reproduction of the measured ${}^{57}\mathrm{Co}(n,xp$) cross sections for the entire neutron energy range. The observed discrepancies at higher energies between the experimental data and the predictions of both the jeff-3.3 library and the talys-1.8 calculations with default parameters indicate the need of new evaluations for this reaction.

Ground and isomeric states of the neutron-deficient odd-$A$ isotopes ${}^{183}\mathrm{Hg}, {}^{185}\mathrm{Hg}$, and ${}^{187}\mathrm{Hg}$ are described from a microscopic calculation based on a self-consistent, axially deformed Hartree-Fock mean field with the Skyrme functional and pairing within BCS approximation. For each equilibrium shape and different odd-neutron states, results on mean-square charge radii and magnetic dipole moments are given and analyzed in the context of their sensitivity to the nuclear deformation and to the spin and parity. Spin-isospin correlations within proton-neutron quasiparticle random phase approximation are then introduced in the nuclear states to obtain the distributions of Gamow-Teller strength and the ${\beta }^{+}/EC$ half-lives of these isotopes, whose measurements are planned at ISOLDE-CERN using total absorption $\gamma$-ray spectroscopy techniques.

The $\beta$-decay strength function of nuclides produced in fission is important as it dictates the distribution of decay energy between electrons, neutrinos, and $\gamma$ rays and so is critical for calculating decay heat in reactors and for estimating the reactor antineutrino spectrum. Several experimental techniques are available to determine this strength function, including electron spectroscopy, $\gamma$-ray calorimetry (TAGS spectroscopy), and detailed, high-resolution spectroscopy with modern large high-purity germanium arrays. This work investigates the decay of the well-known and strongly produced fission fragment ${}^{141}\mathrm{Ba}$. A beam of ${}^{141}\mathrm{Cs}$ was implanted at the target position of the Gammasphere and the subsequent decay of the daughter ${}^{141}\mathrm{Ba}$ was studied. Extensive decay spectroscopy was possible up to the decay $Q$ value of 3.197(7) MeV, including a significant extension of the level scheme and detailed angular correlation measurements for all levels with greater than $0.25\%\beta$ feeding. The distribution of the $\beta$-decay strength was then inferred and compared to previous calorimetric studies. The agreement was excellent and provides a benchmark for comparing strength function methods and data for a more detailed understanding of the structure of ${}^{141}\mathrm{La}$.

A comprehensive study of $\alpha$ particle emergence from ${}^{188\text{–}218}\mathrm{Po}$ isotopes is carried out within the framework of the preformed cluster model (PCM). The mass asymmetry coordinate and the interfragment separation play crucial roles in the identification of the most probable decay channel and the barrier penetration of decay fragments. First, the barrier characteristics are studied using two choices of radii [with surface diffuseness ($C_i$) and without surface diffuseness ($R_i$)]. The fragmentation behavior of ${}^{188}\mathrm{Po}$, ${}^{202}\mathrm{Po}$, and ${}^{218}\mathrm{Po}$ isotopes is explored for the identification of the most probable decay channel in view of the structure of the fragmentation potential. The $\alpha$ decay is found to be the most prominent decay mode in the chosen set of isotopes. The preformation and penetrative probability of the decay fragments is studied with respect to increase in the neutron number of the parent nucleus. The $\alpha$ decay half-lives of polonium isotopes are calculated using classical assault frequency (${\nu }_c$) and quantum mechanical assault frequency (${\nu }_q$) and a comparison is made with the experimental data. Here, the term assault frequency is basically the impinging frequency of an $\alpha$ particle near the surface of the parent nucleus. Further, the $\alpha$ decay half-lives of the ${}^{198\text{–}220}\mathrm{Rn}$ isotopes are calculated using the effective assault frequency (${\nu }_e$) parameter, and a comparison is made with the available experimental data.

The experimental $\gamma$-ray strength functions ($\gamma \mathrm{SFs}$) of ${}^{142,144–151}\mathrm{Nd}$ have been studied for $\gamma$-ray energies up to the neutron separation energy using the Oslo method. The results represent a unique set of $\gamma \mathrm{SFs}$ for an isotopic chain with increasing nuclear deformation. The data reveal how the low-energy enhancement, the scissors mode, and the pygmy dipole resonance evolve with nuclear deformation and mass number. This indicates that the mechanisms behind the low-energy enhancement and the scissors mode are decoupled from each other.

Searches for new americium isotopes with neutron number around 126 are made in bombardments of ${}^{191,193}\mathrm{Ir}$ targets with ${}^{40}\mathrm{Ar}$ ions by employing the gas-filled recoil separator SHANS and the recoil-$\alpha$ correlation technique. No evidence for nuclides of interest is obtained, and the upper limits of the cross sections producing the evaporation residues are estimated to be 31.4 pb and 5.4 pb for the reactions of ${}^{40}\mathrm{Ar}+{}^{193}\mathrm{Ir}$ and ${}^{40}\mathrm{Ar}+{}^{191}\mathrm{Ir}$, respectively. We have performed microscopic finite-temperature Skyrme Hartree-Fock$+$ (Bardeen- Cooper- Schripffer theory) BCS calculations, and found that the fission barriers of compound nuclei in this region decrease rapidly with increasing proton number. The non-observation of new americium isotopes would be attributed to small survival probabilities of the ${}^{231}\mathrm{Am}$ and ${}^{233}\mathrm{Am}$ compound nuclei due to their much reduced fission barriers at high excitations.

Isobar collisions, which were thought to have the same background and different magnetic fields, provide an opportunity to verify the chiral magnetic effect (CME) in relativistic heavy-ion collisions. However, the first result from the RHIC-STAR isobar experiment did not observe the CME signal, but discovered that the backgrounds are different between ${}_{44}{}^{96}\mathrm{Ru}+{}_{44}{}^{96}\mathrm{Ru}$ and ${}_{40}{}^{96}\mathrm{Zr}+{}_{40}{}^{96}\mathrm{Zr}$ collisions. We test eighteen cases of Woods-Saxon parameter settings resulting from different nuclear deformation or nuclear structure effects using a mutiphase transport model. We find out that seven cases can reasonably reproduce three reference ratios measured by the STAR experiment. Considering both the halo-type neutron skin structure and CME-like charge separation, we demonstrate that it is difficult for the CME observables ($\mathrm{\Delta }\delta , \mathrm{\Delta }\delta$ ratio, $\mathrm{\Delta }\gamma$, and $\mathrm{\Delta }\gamma$ ratio) to distinguish the presence or absence of the CME, if the CME strength is weak in isobar collisions. It is because the final state interactions significantly weaken the initial CME signal, resulting in nonlinear sensitivities of the CME observables to the CME strength. Therefore, more sensitive observables are required to search for the possible small CME signal in isobar collisions.

We compile experimental data for the averaged transverse momentum ($\langle p_T\rangle$) of proton, $\mathrm{\Lambda }, {\mathrm{\Xi }}^{-}, {\mathrm{\Omega }}^{-}$, and $\varphi$ at midrapidity in Au$+$Au collisions at $\sqrt{s_{NN}}=$ 200, 39, 27, 19.6, 11.5, 7.7 GeV and in Pb$+$Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV, and find that experimental data of these hadrons exhibit systematic correlations. We apply a quark combination model with equal-velocity combination approximation to derive analytic formulas of hadronic $\langle p_T\rangle$ in the case of exponential form of quark $p_T$ spectra at hadronization. We use them to successfully explain the systematic correlations exhibited in $\langle p_T\rangle$ data of $p\mathrm{\Lambda }, \mathrm{\Lambda }{\mathrm{\Xi }}^{-}, {\mathrm{\Xi }}^{-}{\mathrm{\Omega }}^{-}$, and ${\mathrm{\Xi }}^{-}\varphi$ pairs. We also use them to successfully explain the regularity observed in $\langle p_T\rangle$ of these hadrons as the function of $(d{N}_{\text{ch}}/dy)/\left(0.5N_{\text{part}}\right)$ at midrapidity in central heavy-ion collisions at both Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. Our results suggest that the constituent quark degrees of freedom and the equal-velocity combination of these constituent quarks at hadronization play an important role in understanding $\langle p_T\rangle$ correlations of baryons and $\varphi$ meson in heavy-ion collisions at these RHIC and LHC energies.

We study charmonium dissociation in hot medium with a finite baryon chemical potential ${\mu }_B$. Charmonium bound states are dissociated in the medium by the color screening effect and the random scatterings with thermal partons, which are included in the real and imaginary parts of the potential, respectively. The $J/\psi$ fraction in the $c\overline{c}$ pair defined to be the quantum overlap between the wave package and the wave function of the $J/\psi$ eigenstate decreases with time due to the complex potentials. When ${\mu }_B$ is large compared with the medium temperature, the Debye mass is increased evidently. We consider the ${\mu }_B$-dependent Debye mass in both real and imaginary parts of the potential to calculate the $J/\psi$ survival probability in the static medium and the Bjorken medium. The $J/\psi$ survival probability is reduced evidently by the ${\mu }_B$ effect at low temperatures available in the medium produced in the Beam Energy Scan experiments, while this effect is not apparent at high temperatures.

In high-energy collisions, a dense, strongly interacting medium could be created, the quark gluon plasma. In rapid expansion from the soup of quarks and gluons a gas of resonance and stable particles is formed at the chemical freeze-out and after that as the system cools down, the kinetic freeze-out takes place and interaction between particles ceases. By measuring resonance ratios one could get information about the dominant physical processes in the intermediate temperature ranges, i.e., between the chemical and the kinetic freeze-out. These quantities are measured at the Relativistic Heavy Ion Collider and Large Hadron Collider energies. In the present analysis we employ the hadron resonance gas model assuming partial chemical equilibrium to characterize these measured data. We calculate the ratios of several resonances to their stable counterpart and compare these model calculations to available experimental data.

Data on electromagnetic form factors of proton, neutron, and $\mathrm{\Lambda }$ from annihilation and scattering reactions are collected and interpreted in the frame of a generalized picture of the internal structure of baryons which holds in space-like and time-like regions. It is shown that these data give an insight into the spatial structure of the baryon for distances 100 times smaller than the baryon size and, in the time-like region, a vision of the time evolution of the hadronic matter for times up to ${10}^{-25}$ s, that is two orders of magnitude shorter than the time taken by the light to cross the volume of a proton. In the proposed interpretation, the electric form factor of the proton in the space-like region cannot cross zero, but vanishes or stays very small, as an extrapolation of the data seems to show. In the time-like region specific structures appearing in the data give evidence of the dominance of the quark-diquark underlying dynamics in a well-determined time interval during the evolution of the system.

We study the spatial correlation of a particle-hole pair in the isovector channel in ${}^{56}\mathrm{Co}$ and ${}^{40}\mathrm{K}$ nuclei. To this end, we employ the $\text{Hartree-Fock}+\text{Tamm-Dancoff}$ approximation with the Skyrme interaction. We find a large concentration of the two-body density at positions where the neutron particle and the proton hole states locate on the opposite side to each other with respect to the core nucleus. This feature originates from a repulsive nature of the isovector residual interaction, which is in stark contrast to the dineutron correlation with an attractive pairing interaction between the valence neutrons discussed, e.g., in ${}^{11}\mathrm{Li}$ and ${}^6\mathrm{He}$.

Background: Equations of state for a cold neutron star's interior are presented in three-column tables that relate the baryonic density, the energy density, and the pressure. A few analytical expressions for those tables have been established these past two decades as a convenient way to present a large number of nuclear models for neutron-star matter. Some of those analytical representations are based on nonunified equations of state, in the sense that the high- and the low-density part of the star are not computed with the same nuclear model.

Purpose: Fits of equations of state based on a piecewise polytropic representation are revised by using unified tables of equations of state, that is to say, models which have been calculated consistently for the core and the crust.

Methods: A set of 52 unified equations of state is chosen. Each one is divided in seven polytropes via an adaptive segmentation, and two parameters per polytrope are fit to the tabulated equation of state. The total mass, radius, tidal deformability, and moment of inertia of neutron stars are modeled from the fits and compared with the quantities calculated from the original tables to ensure the accuracy of the fits on macroscopic parameters.

Results: We provide the polytropes parameters for 15 nucleonic relativistic mean-field models, seven hyperonic relativistic mean-field models, five hybrid relativistic mean-field models, 24 nucleonic Skyrme models, and one ab initio model.

Conclusions: The fit error on the macroscopic parameters of neutron stars is small and well within the estimated measurement accuracy from current and next-generation telescopes.

For the first time, within the framework of the dynamical cluster-decay model (DCM) by Gupta and collaborators, we provide reasonable estimations for cross sections of nuclear systems which will give rise to new superheavy elements. The important point and the new approach presented in this contribution are the theoretical calculations done without tracking any reference to experimental data; i.e., these are independent calculations. We will provide a method for reasonable estimates for the cross sections of unobserved possible decay channels in a nuclear reaction. We will demonstrate the capability of the DCM to give a probable/sensible range of the cross section. This exercise of theoretical calculations within the DCM may benefit experiments for the discovery of new superheavy elements. Our results can provide hints to the experimentalist to choose proper incoming channels in order to perform experiments. We have applied this new strategy to calculate the cross sections of the already studied compound nuclei $Z=116$ and 118 via hot fusion reactions, and observed that our calculated range of cross sections has given values within the reach of experimental studies. Both compound nuclei were studied earlier by one of the authors for the angle $\mathrm{\Phi }=0^{\circ }$, including quadrupole deformations, ${\beta }_{2i}$ alone with “optimum” orientations (${\theta }_{\mathrm{opt}.}$). Here, we consider the same specifications in order to study the new approach using the DCM. The principal aim of this work is to study the capability of the DCM to determine the cross sections for new elements, where experimental data are not available.

We study neutrinoless double-$\beta$ decay in an effective field theory (EFT) for heavy nuclei, which are treated as a spherical core coupled to additional neutrons and/or protons. Since the low-energy constants of the EFT cannot be fitted to data for this unobserved decay, we follow an alternative strategy to constrain these through a correlation with double Gamow-Teller transitions. This correlation was recently found to hold for shell-model calculations, energy-density functionals, and other nuclear structure models. We therefore first calculate the nuclear matrix elements for double Gamow-Teller transitions in the EFT for heavy nuclei. The combination of the EFT uncertainty with the correlation uncertainty enables predictions of nuclear matrix elements for neutrinoless double-$\beta$ decay for a broad range of isotopes with quantified uncertainties. Generally the EFT predicts smaller nuclear matrix elements compared to other approaches, but our EFT results are consistent with recent ab initio calculations.

We compute spectral function for ${}^4\mathrm{He}$ by combining coupled-cluster theory with an expansion of integral transforms into Chebyshev polynomials. Our method allows us to estimate the uncertainty of spectral reconstruction. The properties of the Chebyshev polynomials make the procedure numerically stable and considerably lower in memory usage than the typically employed Lanczos algorithm. We benchmark our predictions with other calculations in the literature and with electron-scattering data in the quasi-elastic peak. The spectral function formalism allows one to extend ab initio lepton-nucleus cross sections into the relativistic regime. This makes it a promising tool for modeling this process at higher-energy transfers. The results we present open the door for studies of heavier nuclei, important for the neutrino oscillation programs.