One-neutron stripping and pickup cross sections in the ${}^6\mathrm{Li}+{}^{124}\mathrm{Sn}$ system have been investigated through coupled-channel calculations by using a reliable global set of potentials. The systematics of one-neutron stripping and pickup cross sections with ${}^6\mathrm{Li}$ projectiles on several targets have been presented. An approximate universal behavior is seen, which has been explained by a model based on barrier penetration. The neutron transfer along with cumulative sum of complete and incomplete fusion was found to explain most of the reaction cross section in the ${}^6\mathrm{Li}+{}^{124}\mathrm{Sn}$ system.

In this article, we investigate $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Pb}+\mathrm{Pb}$ collision systems to understand the (multi-) strange hadron production at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies using the Monte Carlo $\mathrm{HYDJET}++$ model. We study the $p_T$ spectra, particle ratios, and strangeness enhancement factor for (multi-) strange hadrons. The $p_T$ spectra of $K^{+}\left(K^{-}\right)$, $K_s^0$, $\mathrm{\Lambda }\left(\overline{\mathrm{\Lambda }}\right)$, ${\mathrm{\Xi }}^{-}\left({\overline{\mathrm{\Xi }}}^{+}\right)$, and ${\mathrm{\Omega }}^{-}\left({\overline{\mathrm{\Omega }}}^{+}\right)$ are shown for both $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Pb}+\mathrm{Pb}$ collision systems in various centrality intervals. We find that the strange quark thermalization might not be achieved by the model for multistrange baryons toward peripheral collisions. The $p_T$-differential particle ratios, focused on strange hadron-to-meson ratios, are reported for 0–5% and 40–60% centrality intervals for both the collision systems. We observe an enhancement in the particle ratios at intermediate $p_T$ region. $p_T$ integrated strange-to-nonstrange ratios suggest that chemical equilibrium might not be achieved for multistrange hadrons. We report the strangeness enhancement factor for $\mathrm{\Lambda }\left(\overline{\mathrm{\Lambda }}\right)$, ${\mathrm{\Xi }}^{-}\left({\overline{\mathrm{\Xi }}}^{+}\right)$, and ${\mathrm{\Omega }}^{-}+{\overline{\mathrm{\Omega }}}^{+}$ at both RHIC and LHC energies. An increase in the enhancement factor is observed with the increase in strangeness content of the baryons. We also observe that enhancement is higher in $\mathrm{Au}+\mathrm{Au}$ collisions than in $\mathrm{Pb}+\mathrm{Pb}$ collisions. Further, we compare the $\mathrm{HYDJET}++$ results with the experimental data and various other simulation models, wherever possible.

Background: Nuclear reactions involving $\alpha$ particles play an important role in various astrophysical processes such as the $\gamma$ process of heavy element nucleosynthesis. The poorly known low-energy $\alpha$-nucleus optical potential is a key parameter to estimate the rates of these reactions.

Purpose: The $\alpha$-nucleus optical potential can be tested by measuring the cross section of $\alpha$ scattering as well as $\alpha$-induced reactions. Low energy elastic $\alpha$ scattering on ${}^{144}\mathrm{Sm}$ has recently been measured with high precision. The aim of the present work was to complement that work by measuring the $(\alpha ,n)$ cross sections on ${}^{144}\mathrm{Sm}$ at low energies. The experimental data shall be used to constrain the $\alpha$-nucleus optical model potential. From this potential the ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$ reaction rate can be derived with reduced uncertainties.

Method: The ${}^{144}\mathrm{Sm}(\alpha ,n){}^{147}\mathrm{Gd}$ reaction was studied by bombarding Sm targets with $\alpha$ beams provided by the cyclotron accelerator of Atomki. The cross section was determined using the activation method. The $\gamma$ radiation following the decay of the ${}^{147}\mathrm{Gd}$ reaction product was measured with a high-purity germanium (HPGe) detector. The experimental data are analyzed within the statistical model.

Results: The cross section was measured in the $\alpha$-energy range between 13 and 20 MeV in 1 MeV steps, i.e., from close above the $(\alpha ,n)$ threshold. The results were compared with statistical model calculations using various approaches and parametrizations for the $\alpha$-nucleus optical potential, and excellent agreement was obtained for two recent potentials. However, these potentials cannot reproduce literature data for the ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$ reaction with the same accuracy.

Conclusions: Constraints for the $\alpha$-nucleus potential were derived from an analysis of the new ${}^{144}\mathrm{Sm}(\alpha ,n){}^{147}\mathrm{Gd}$ data and literature data for ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$. These constraints enable a determination of the reaction rate of the ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$ reaction with significantly reduced uncertainties of less than a factor of 2.

The multiphase transport model (AMPT) is used to study the final-state effects on the symmetric correlations (SC), asymmetric correlations (ASC), normalized symmetric correlations (NSC), and normalized asymmetric correlations (NASC) in $\mathrm{Au}+\mathrm{Au}$ collisions at 200 GeV. The correlators' sensitivity to nonflow effects associated with long- and short-range nonflow correlations are also discussed using the HIJING model. The results indicate that SC, ASC, NSC, and NASC can give accompanying constraints for initial- and final-state effects. In addition, conducting further detailed experimental measurements spanning a broad range of collision systems and beam energies will serve as an additional constraint for the theoretical models' calculations.

Flerovium isotopes (element $Z=114$) were produced in the fusion-evaporation reactions ${}^{48}\mathrm{Ca}+{}^{242,244}\mathrm{Pu}$ and studied with an upgraded TASISpec decay station placed in the focal plane of the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Twenty-nine flerovium decay chains were identified by means of correlated implantation, $\alpha$ decay, and spontaneous fission events. Data analysis aspects and statistical assessments, primarily based on measured rates of various events, which laid the foundation for the comprehensive spectroscopic information on the flerovium decay chains, are presented in detail. Various decay scenarios of an excited state observed in ${}^{282}\mathrm{Cn}$ are examined in depth with the help of Geant4 simulations and assessed by predictions of beyond mean-field calculations including triaxial shape degrees of freedom. Previous, revised, and newly derived fission probabilities of even-even superheavy nuclei are compared with various theoretical predictions.

We show that the Hartree-Fock-Bogoliubov (HFB) method is able to describe experimental values of $\alpha$ decay widths by including a residual nucleon-nucleon surface Gaussian interaction (SGI) within the standard procedure used to calculate the nuclear mean field. We call this method the cluster HFB (CHFB) approach. In this way we correct the deficient asymptotic behavior of the corresponding single-particle wave functions generated by the standard mean field. The corrected mean field becomes a sum between the standard mean Woods-Saxon–like field and a cluster Gaussian component centered at the same radius as the SGI. Thus, we give a confirmation of the mean field plus cluster potential structure, which was assumed in our previous work on $\alpha$-decay widths. Systematic calculations evidence the linear correlation between the SGI strength and fragmentation potential, allowing for reliable predictions concerning the half-lives of superheavy emitters.

The Jost function method is extended within the framework of the random phase approximation (RPA) theory to find poles on the complex energy plane that exhibit complex RPA eigenenergies. Poles corresponding to the RPA excited states such as the giant resonance of ${}^{16}\mathrm{O}$ electric dipole excitations were successfully found on the complex energy plane. Although the giant resonance has been known as a single resonance with large strength and width, it is found that, at least within the RPA framework, the ${}^{16}\mathrm{O}$ electric dipole giant resonance is formed by multiple poles, each of which is an independent pole with different widths, origins, response properties to residual interactions, and components structures of the density fluctuation.

We argue that two seemingly different phenomena, namely the well-known saturation of the Hagedorn exponential distribution and the less familiar saturation of Regge trajectories at resonance masses $m\approx$ 2–2.5 GeV, are related and have the same origin: quark deconfinement. We show that the slope of the real part of nonlinear Regge trajectories determines the prefactor $f\left(m\right)$ in Hagedorn's resonance mass density distribution $\rho \left(m\right)$. While the Hagedorn distribution comes from statistics, Regge trajectories contain dynamics.

Fifteen correlated $\alpha$-decay chains starting from the odd-$A$ superheavy nucleus ${}^{289}\mathrm{Fl}$ were observed following the fusion-evaporation reaction ${}^{48}\mathrm{Ca}+{}^{244}\mathrm{Pu}$. The results call for at least two parallel $\alpha$-decay sequences starting from at least two different states of ${}^{289}\mathrm{Fl}$. This implies that close-lying levels in nuclei along these chains have quite different spin-parity assignments. Further, observed $\alpha$-electron and $\alpha$-photon coincidences, as well as the $\alpha$-decay fine structure along the decay chains, suggest a change in the ground-state spin assignment between ${}^{285}\mathrm{Cn}$ and ${}^{281}\mathrm{Ds}$. Our experimental results, on the excited level structure of the heaviest odd-$N$ nuclei to date, provide a direct testing ground for theory. This is illustrated by comparison with new nuclear structure calculations based on the symmetry-conserving configuration mixing theory.

We present the first measurements of transverse momentum spectra of ${\pi }^{\pm }, K^{\pm }, p\left(\overline{p}\right)$ at midrapidity ($\left|y\right|<0.1$) in $\text{U}+\text{U}$ collisions at $\sqrt{s_{NN}}$= 193 GeV with the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The centrality dependence of particle yields, average transverse momenta, particle ratios and kinetic freeze-out parameters are discussed. The results are compared with the published results from $\text{Au}+\text{Au}$ collisions at $\sqrt{s_{NN}}$= 200 GeV in STAR. The results are also compared to those from A Multi-Phase Transport (ampt) model.

We present a Bayesian method to reconstruct event-by-event multiplicity fluctuations and rapidity correlations in $p+\mathrm{Pb}$ collisions at zero impact parameter from minimum-bias data, without assuming any model of the collision dynamics. We test it on Monte Carlo simulations with the Angantyr model, then apply it to ATLAS data on the distribution of charged multiplicity and transverse energy in $p+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=5.02$ TeV. Fluctuations in $b=0$ collisions are quantum fluctuations which originate mostly from the proton wave function, and therefore have the potential to constrain the subnucleonic structure of the proton. The Angantyr model is found to overestimate fluctuations. In addition, we find that as the rapidity increases (towards the Pb-going side), not only the multiplicity density increases, but also its relative event-by-event fluctuation. This counterintuitive phenomenon is also observed in simulations with Angantyr, and with the quantum chromodynamics dipole model, where its origin can be traced back to the branching process through which gluons are produced.

We present results of simulations of light-nuclei production in relativistic heavy-ion collisions within the updated Three-fluid Hydrodynamics-based Event Simulator Extended by UrQMD (ultrarelativistic quantum molecular dynamics) final State interactions (theseus). The simulations were performed for $\mathrm{Pb}+\mathrm{Pb}$ and $\mathrm{Au}+\mathrm{Au}$ collisions in the collision energy range of $\sqrt{s_{NN}}=$ 6.4–19.6 GeV. The light-nuclei production is treated within the thermodynamical approach on an equal basis with hadrons. The only additional parameter related to the light nuclei is the energy density of late freeze-out that imitates the afterburner stage of the collision because the light nuclei do not participate in the UrQMD evolution. This parameter is fixed from the condition of the best reproduction of the proton transverse-momentum spectrum after the UrQMD afterburner by that at the late freeze-out. The updated theseus results in an imperfect but reasonable reproduction of data on bulk observables of the light nuclei, especially their functional dependence on the collision energy and light-nucleus mass. Various ratios, $d/p$, $t/p$, $t/d$, and $N\left(t\right)\times N\left(p\right)/N^2\left(d\right)$, are also considered. The directed flow of light nuclei turns out to be more involved. Apparently, it requires explicit treatment of the afterburner evolution of light nuclei that violates the kinetic equilibrium. Imperfect reproduction of the light-nuclei data leaves room for medium effects in produced light nuclei.

We explore the nucleons and $\mathrm{\Delta }$ isobars under strong magnetic fields in Skyrme models. The effects of the derivative dependent sextic term in Skyrme Lagrangian are investigated. When the Skyrmion is quantized, the role of the nondiagonal elements in the kinematical term is discussed. The present work has shown the nontrivial impacts on the properties of the nucleons and $\mathrm{\Delta }$ isobars.

We have done a theoretical study of the $\gamma d\to {\pi }^0\eta d$ reaction starting with a realistic model for the $\gamma N\to {\pi }^0\eta N$ reaction that reproduces cross sections and polarization observables at low energies and involves the $\gamma N\to \mathrm{\Delta }\left(1700\right)\to \eta \mathrm{\Delta }\left(1232\right)\to \eta {\pi }^{0}N$ process. For the coherent reaction in the deuteron we considered the impulse approximation together with the rescattering of the pions and the $\eta$ on a different nucleon than the one where they are produced. We found this second mechanism very important since it helps share between two nucleons the otherwise large momentum transfer of the reaction. Other contributions to the $\gamma d\to {\pi }^0\eta d$ reaction, involving the $\gamma N\to {\pi }^{\pm }{\pi }^0{N}^{\prime }$ process, followed by the rescattering of the ${\pi }^{\pm }$ with another nucleon to give $\eta$ and a nucleon, have also been included. We find a natural explanation, tied to the dynamics of our model, for the shift of the $\eta \text{−}d$ mass distribution to lower invariant masses, and of the ${\pi }^0\text{−}d$ mass distribution to larger invariant masses, compared to a phase space calculation. We also study theoretical uncertainties related to the large momenta of the deuteron wave function involved in the process as well as to the couplings present in the model. Striking differences are found with the experimental angular distribution and further theoretical investigations might be necessary.

Neutron stars explore matter at the highest densities in the universe such that their inner cores might undergo a phase transition from hadronic to exotic phases, e.g., quark matter. Such a transition could be associated with nontrivial structures in the density behavior of the speed of sound, such as jumps and sharp peaks. Here, we employ a physics-agnostic approach to model the density dependence of the speed of sound in neutron stars and study to what extent the existence of nontrivial structures can be inferred from existing astrophysical observations of neutron stars. For this, we exhaustively study different equations of state, including as well those with explicit first-order phase transitions. We obtain a large number of different equation of states which reproduce the same astrophysical observations and obey the same physical constraints, such as mechanical stability and causality. Among them, some have nontrivial structures in the sound speed whereas others do not. We conclude that astrophysical information to date do not require the existence of a phase transition to quark matter in the density range explored in the core of neutron stars.

Generating an ensemble of equations of state that fulfill multimessenger constraints, we statistically determine the properties of dense matter found inside neutron stars (NSs). We calculate the speed of sound and trace anomaly and demonstrate that they are driven towards their conformal values at the center of maximally massive NSs. The local peak of the speed of sound is shown to be located at values of the energy and particle densities, which are consistent with deconfinement and percolation conditions in QCD matter. We also analyze fluctuations of the net-baryon number density in the context of possible remnants of critical behavior. We find that the global maxima of the variance of these fluctuations emerge at densities beyond those found in the interiors of NSs.

Neutron-proton equilibration has previously been studied experimentally in dynamically deformed nuclei in heavy ion collisions [Phys. Rev. Lett. 118, 062501 (2017); Phys. Rev. C 95, 044604 (2017)] using the NIMROD detector array at the Cyclotron Institute at Texas A&M University. Results indicated the composition of the two heaviest fragments originating from the excited projectile-like fragment evolved exponential with respect to their orientation angle to be more similar. Constrained Molecular Dynamics and Antisymmetrized Molecular Dynamics simulations were performed for different formulations of the density dependence of the asymmetry energy term of the nuclear equation of state. The simulations are compared to experimental results, which indicate a better agreement with a softer interaction in the nuclear equation of state.

A novel practical few-body method is formulated to include isospin symmetry for nuclear halo structures. The method is designed to describe $\beta$ decay, where the basic concept of isospin symmetry facilitates a proper understanding. Both isobaric analog and antianalog states are treated. We derive general and explicit formulas for three-body systems using hyperspherical coordinates. The example of the $\beta$ decaying ${}^{11}\mathrm{Li}$ (${}^9\mathrm{Li}+n+n$) is chosen as a challenging application for numerical calculations of practical interest. The detailed results are compared to existing experimental data, and good agreement is found at high excitation energies, where the isobaric analog and antianalog states are situated in the daughter nucleus. An interpretation of the decay pattern at lower excitation energies is suggested. Decays of the ${}^9\mathrm{Li}$ core and the two halo neutrons are individually treated and combined with the daughter system with almost unique isospin, which we predict to be broken by about $0.4\%$ probability. Properties of decay products are predicted as possible future tests of this model.

Using the GABRIELA detector array, $\gamma$-ray and internal-conversion-electron decay spectroscopy has been performed on ${}^{255}\mathrm{Rf}$ nuclei that were produced via the ${}^{207}\mathrm{Pb}({}^{50}\mathrm{Ti},2n){}^{255}\mathrm{Rf}$ fusion-evaporation reaction using the SHELS velocity filter. Three isomers were identified in ${}^{255}\mathrm{Rf}$ with the aid of Geant4 simulations. The existence of two high-$K$ isomeric states in cascade has been confirmed. Possible three-quasiparticle configurations involving the coupling of the unpaired $9/2^{-}\left[734\right]$ neutron to two-quasiparticle states have been suggested and a likely decay scenario has been proposed on the basis of comparisons to Geant4 simulations. The simulations have also confirmed the existence of the $5/2^{+}\left[622\right]$ spin isomer at low excitation energy.