The reactions ${}^{6,7}\mathrm{Li}+{}^{27}\mathrm{Al}$ were compared with the reactions ${}^{17,18}\mathrm{O}+{}^{16}\mathrm{O}$ which form the same compound nuclei ${}^{33,34}\mathrm{S}$. Cross-section data for the reactions ${}^{6,7}\mathrm{Li}+{}^{27}\mathrm{Al}$ were derived from experimentally determined γ-ray production cross sections for transitions in several residual nuclei. For the reactions ${}^{17,18}\mathrm{O}+{}^{16}\mathrm{O}$ experimental results from the literature were used. It could be shown that the weakly bound projectiles ${}^{6,7}\mathrm{Li}$ undergo not only fusion processes, but also breakup reactions quite in contrast to the tightly bound projectiles ${}^{18}\mathrm{O}$ and ${}^{17}\mathrm{O}$, respectively. Especially below the Coulomb barrier such direct reactions play an important role in competition to complete fusion. Calculations based on the statistical model agree well with the available data for ${}^{17,18}\mathrm{O}+{}^{16}\mathrm{O}$, but failed to represent the behavior of the experimentally determined production cross sections for the evaporation residues in the reactions ${}^{6,7}\mathrm{Li}+{}^{27}\mathrm{Al}$. But coupled-channel codes and calculations based on a nucleus-nucleus proximity potential are able to reproduce the energy dependence of the complete fusion cross sections.

This article reports the first measurement of prompt ${\chi }_{c1}$ and ${\chi }_{c2}$ charmonium production in nuclear collisions at Large Hadron Collider energies. The cross-section ratio $\sigma \left({\chi }_{c2}\right)/\sigma \left({\chi }_{c1}\right)$ is measured in $p\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=8.16$ TeV, collected with the LHCb experiment. The ${\chi }_{c1,2}$ states are reconstructed via their decay to a $J/\psi$ meson, subsequently decaying into a pair of oppositely charged muons, and a photon, which is reconstructed in the calorimeter or via its conversion in the detector material. The cross-section ratio is consistent with unity in the two considered rapidity regions. Comparison with a corresponding cross-section ratio previously measured by the LHCb Collaboration in $pp$ collisions suggests that ${\chi }_{c1}$ and ${\chi }_{c2}$ states are similarly affected by nuclear effects occurring in $p\mathrm{Pb}$ collisions.

Spin-isospin transitions in nuclei away from the valley of stability are essential for the description of astrophysically relevant weak interaction processes. While they remain mainly beyond the reach of experiment, theoretical modeling provides important insight into their properties. In order to describe the spin-isospin response, the proton-neutron relativistic quasiparticle random phase approximation is formulated using the relativistic density-dependent point coupling interaction, and separable pairing interaction in both the $T=1$ and $T=0$ pairing channels. By implementing recently established DD-PCX interaction with improved isovector properties relevant for the description of nuclei with neutron-to-proton number asymmetry, the isobaric analog resonances (IAR) and Gamow-Teller resonances (GTR) have been investigated. In contrast to other models that usually underestimate the IAR excitation energies in Sn isotope chain, the present model accurately reproduces the experimental data, while the GTR properties depend on the isoscalar pairing interaction strength. This framework provides not only an improved description of the spin-isospin response in nuclei, but it also allows future large-scale calculations of charge-exchange excitations and weak interaction processes in stellar environment.

The low-lying level structure of ${}^{63}\mathrm{V}$ was studied for the first time by the inelastic proton scattering and the proton knock-out reaction in inverse kinematics. The comparison of the newly observed $\gamma$-ray transitions at 696(8) keV and 889(16) keV with our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja interaction established two excited states proposed to be the first $11/2^{-}$ and $9/2^{-}$ levels. The $(p,p^{\prime })$ excitation cross sections were analyzed by the coupled channel formalism assuming pure quadrupole as well as quadrupole+hexadecapole deformations. This resulted in large deformation parameters placing ${}^{63}\mathrm{V}$ in the island of inversion located below ${}^{68}\mathrm{Ni}$.

A measurement of the ${}^{50}\mathrm{Ti}(d,p){}^{51}\mathrm{Ti}$ reaction at 16 MeV was performed using the Super Enge Split-Pole Spectrograph to measure the magnitude of the $N=32$ subshell gap in Ti. Seven states were observed that had not been observed in previous $(d,p)$ measurements, and the $L$ transfer values for six previously measured states were either changed or measured for the first time. The results were used to determine single neutron energies for the $p_{3/2}$, $p_{1/2}$, and $f_{5/2}$ orbitals. The resulting single neutron energies in ${}^{51}\mathrm{Ti}$ confirm the existence of the $N=32$ gap in Ti. These single neutron energies and those from previous measurements in ${}^{49}\mathrm{Ca}$, ${}^{53}\mathrm{Cr}$, and ${}^{55}\mathrm{Fe}$ are compared to values from a covariant density functional theory calculation.

In the relativistic impulse approximation (RIA), we study symmetry potentials and in-medium nucleon-nucleon $\left(NN\right)$ cross sections with the Nambu–Jona-Lasinio (NJL) model that features chiral symmetry. The chiral symmetry that plays a fundamental role in the nonperturbative physics in the strong interaction is anticipated to add restrictive effects on the symmetry potentials and in-medium $NN$ cross sections. For comparison, we also perform the study with the usual relativistic mean-field (RMF) model. The numerical results with the NJL and RMF models are similar at saturation density and below, since a priori fit was made to saturation properties. With the increase of nuclear density, the chiral symmetry starts to be restored partially in the NJL model, resulting in the explicit fall of the scalar density. In a large energy span, the symmetry potential acquires a significant rise for the partial restoration of the chiral symmetry, compared to the one with the RMF model. It is found that the in-medium $NN$ cross sections in the RIA with the NJL and RMF models both increase with the density in the energy region interested in this study, whereas those with the NJL model increase sharply as long as a clear chiral symmetry restoration takes place. The different tendency of observables in density can be transmitted to the different energy dependence in the RIA. The NJL model is shown to have characteristic energy-dependent symmetry potentials and $NN$ cross sections beyond saturation point, apart from the RMF models.

Penetrating probes in heavy-ion collisions, like jets and photons, are sensitive to the transport coefficients of the produced quark-gluon plasma, such as shear and bulk viscosity. Quantifying this sensitivity requires a detailed understanding of photon emission and jet-medium interaction in a nonequilibrium plasma during the hydrodynamic stages of heavy-ion collisions. Up to now, such an understanding has been hindered by plasma instabilities. These instabilities arise out of equilibrium and lead to spurious divergences when evaluating the rate of interaction of hard probes with the plasma. In this paper, we show that taking into account the time evolution of an unstable plasma cures these divergences. Specifically, we calculate the time evolution of gluon two-point correlators in a setup with a small initial momentum anisotropy and show that the gluon occupation density at first grows exponentially. Based on this calculation, we argue for a phenomenological prescription where instability poles are subtracted. Finally, we show that in the Abelian case instability fields do not affect medium-induced photon emission to our order of approximation.

Hindrance factors for $K$-forbidden $E2$ decays from multiquasiparticle isomers are analyzed in relation to mixing matrix elements that are often associated with chance near degeneracies, and a functional relationship is established. Focusing on effective matrix elements for $\mathrm{\Delta }K=6$ decays from three-quasiparticle isomers, significant configuration dependence is demonstrated.

We investigate the properties of baryonic matter within the framework of the in-medium modified chiral soliton model by taking into account the effects of surrounding baryonic environment on the properties of in-medium baryons. The internal parameters of the model are determined based on nuclear phenomenology at nonstrange sector and fitted by reproducing nuclear matter properties near the saturation point. We discuss the equations of state in different nuclear environments such as symmetric nuclear matter, neutron, and strange matters. We show that the results for the equations of state are in good agreement with the phenomenology of nuclear matter. We also discuss how the SU(3) baryons masses undergo changes in these various types of nuclear matter.

Coupling hadronic kinetic theory models to fluid dynamics in phenomenological studies of heavy ion collisions requires a prescription for “particlization”. Existing particlization models are based on implicit or explicit assumptions about the microscopic degrees of freedom that go beyond the information provided by the preceding fluid dynamical history. We propose an alternative prescription which uses only macroscopic information provided by the hydrodynamic output. This method follows directly from the connections between information theory and statistical mechanics.

We introduce a positive-definite single-particle distribution that is suitable for describing the transition from a macroscopic hydrodynamic to a microscopic kinetic description during the late stages of heavy-ion collisions in the presence of moderately large viscous corrections. The modified equilibrium distribution function can be constructed with hydrodynamic input from either relativistic viscous fluid dynamics or anisotropic fluid dynamics. We test the modified equilibrium distribution's hydrodynamic output for a stationary hadron resonance gas subject to either shear stress, bulk pressure, or baryon diffusion current at a given freeze-out temperature and baryon chemical potential. While it does not reproduce all components of the net baryon current and energy-momentum tensor exactly, it significantly improves upon the customary linearized approximations for the nonequilibrium correction $\delta f_n$ which typically lead to unphysical negative distribution functions at large particle momenta. A comparison of particle spectra and $p_T$–differential elliptic flow coefficients from the Cooper–Frye formula computed with the modified equilibrium distribution and with linearized $\delta f_n$ corrections is presented, for two different $(2+1)$–dimensional hypersurfaces corresponding to central and noncentral $\mathrm{Pb}+\mathrm{Pb}$ collisions at the Large Hadron Collider (LHC).

The question of the number and origin of isomeric states in ${}^{256}\mathrm{Rf}$ arose from two independent experiments but remained unanswered for a decade. To shed light on this puzzle, we studied isomeric decay in ${}^{256}\mathrm{Rf}$ by measuring conversion electrons with fast fully digital electronics. ${}^{256}\mathrm{Rf}$ was produced in the fusion-evaporation reactions of ${}^{50}\mathrm{Ti}+{}^{207}\mathrm{Pb}$ and ${}^{50}\mathrm{Ti}+{}^{208}\mathrm{Pb}$ at the gas-filled recoil separator TransActinide Separator and Chemistry Apparatus. Among a total of 120 decays of ${}^{256}\mathrm{Rf}$, we detected 22 and 12 decays proceeding through one and two isomeric states. Half-lives of the low- and higher-lying states were assigned to be $T_{1/2}={14}_{-4}^{+6}$ and ${10}_{-3}^{+5}\mu \mathrm{s}$, respectively. Population rates of these isomeric states were estimated to be $\approx 18\%$ and $>10\%$, which are similar to those for two-quasiparticle $K$ isomeric states in this region of nuclei. The results, thus, confirm an earlier claim on the existence of multiple $K$ isomeric states in ${}^{256}\mathrm{Rf}$ and show their population rates are as high as in No isotopes. Suggestively, $K$ remains a good quantum number in isotopes of heavier elements like Sg and Hs, where yet unknown high-$K$ isomeric states still could exist. The present experimental results demonstrate that the “triggerless” measurement guarantees an efficient detection of delayed conversion electron signals. Thus, it is a very efficient method for the identification of isomeric states in experiments with one nucleus-at-a-time production rates.

Background: Time-dependent techniques in nuclear theory often rely on mean-field or Hartree-Fock descriptions. Beyond-mean-field dynamical calculations within the time-dependent density matrix (TDDM) theory have often invoked symmetry restrictions and ignored the connection between the mean field and the induced interaction.

Purpose: We study the ground states obtained in a TDDM approach for nuclei from $A=12$ to $A=24$, including examples of even-even and odd-even nuclei with and without intrinsic deformation. We overcome previous limitations using three-dimensional simulations and employ density-independent Skyrme interactions self-consistently.

Methods: The correlated ground states are found starting from the Hartree-Fock solution, by adiabatically including the beyond-mean-field terms in real time.

Results: We find that, within this approach, correlations are responsible for $\approx 4–5\%$ of the total energy. Radii are generally unaffected by the introduction of beyond-mean-field correlations. Large nuclear correlation entropies are associated with large correlation energies. By all measures, ${}^{12}\mathrm{C}$ is the most correlated isotope in the mass region considered.

Conclusions: Our work is the starting point of a consistent implementation of the TDDM technique for applications into nuclear reactions. Our results indicate that correlation effects in structure are small, but beyond-mean-field dynamical simulations could provide insight into several issues of interest.

Monoenergetic muon neutrinos at 236 MeV are readily produced in intense medium-energy proton facilities $(\gtrsim 2–3\mathrm{GeV})$ when a positive kaon decays at rest (KDAR; $K^{+}\to {\mu }^{+}{\nu }_{\mu }$). These neutrinos provide a unique opportunity to both study the neutrino interaction and probe the nucleus with a monoenergetic weak-interaction-only tool. We present cross-section calculations for quasielastic scattering of these 236-MeV neutrinos off ${}^{12}\mathrm{C}$ and ${}^{40}\mathrm{Ar}$, paying special attention to low-energy aspects of the scattering process. Our model takes the description of the nucleus in a mean-field approach as the starting point, where we solve Hartree-Fock equations using a Skyrme type nucleon-nucleon interaction. Thereby, we introduce long-range nuclear correlations by means of a continuum random-phase approximation (CRPA) framework where we solve the CRPA equations using a Green's function method. The model successfully describes ($e,e^{\prime }$) data on ${}^{12}\mathrm{C}$ and ${}^{40}\mathrm{Ca}$ in the kinematic region that overlaps with the KDAR ${\nu }_{\mu }$ phase space. In addition to these results, we present future prospects for precision KDAR cross-section measurements and applications of our calculations in current and future experiments that will utilize these neutrinos.

The determination of nuclear symmetry energy and, in particular, its density dependence is a long-standing problem for the nuclear physics community. Previous studies have found that the product of electric dipole polarizability ${\alpha }_D$ and symmetry energy at saturation density $J$ has a strong linear correlation with $L$, the slope parameter of symmetry energy. However, the current uncertainty of $J$ hinders the precise constraint on $L$. We investigate the correlations between electric dipole polarizability ${\alpha }_D$ (or times symmetry energy at saturation density $J$) in Sn isotopes and the slope parameter of symmetry energy $L$ using the quasiparticle random-phase approximation based on the Skyrme Hartree-Fock-Bogoliubov model. A strong linear correlation between ${\alpha }_D$ and $L$ is found in neutron-rich Sn isotopes where pygmy dipole resonance (PDR) gives a considerable contribution to ${\alpha }_D$, attributed to the pairing correlations playing important roles through PDR. This newly discovered linear correlation would help one to constrain $L$ and neutron-skin thickness $\mathrm{\Delta }{R}_{n}p$ stiffly if ${\alpha }_D$ is measured with high resolution in neutron-rich nuclei. Additionally, a linear correlation between ${\alpha }_{D}J$ in a nucleus around the $\beta$-stability line and ${\alpha }_D$ in a neutron-rich nucleus can be used to assess ${\alpha }_D$ in neutron-rich nuclei.

The generator coordinate method (GCM) combined with the projection method is applied to large-scale shell-model calculations. The quadrupole deformation is taken as a generator coordinate and the GCM basis states are prepared by the quadrupole-constrained Hartree-Fock Bogoliubov method with the variation after particle-number projection. The resultant GCM wave function is a linear combination of the angular-momentum and parity projected basis states. We discuss how well the present method approximates the exact solution of the shell-model diagonalization method by the benchmark tests of ${}^{48}\mathrm{Ca}$, ${}^{56}\mathrm{Ni}$, and ${}^{48}\mathrm{Cr}$ in the $pf$-shell model space and those of ${}^{132}\mathrm{Ba}$ and ${}^{133}\mathrm{Ba}$ in the $50<N,Z<82$ model space.

We explore theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions by examining the full nonlinear causality conditions and quantifying the second-order transport coefficients' role on flow observables. The causality conditions impose physical constraints on the maximum allowed values of inverse Reynolds numbers during the hydrodynamic evolution. Including additional second-order gradient terms in the Denicol-Niemi-Molnár-Rischke (DNMR) theory significantly shrinks the casual regions compared to those in the Israel-Stewart hydrodynamics. For $\mathrm{Au}+\mathrm{Au}$ collisions, we find the variations of flow observables are small with and without imposing the necessary causality conditions, suggesting a robust extraction of the quark-gluon plasma's transport coefficients in previous model-to-data comparisons. However, sizable sensitivity is present in small $p+\mathrm{Au}$ collisions, which poses challenges to study the small systems' collectivity.

Ternary fission of actinides probes the state of the nucleus at scission. Light clusters are produced in space and time very close to the scission point. Within the nonequilibrium statistical operator method, a generalized Gibbs distribution is constructed from the information given by the observed yields of isotopes. Using this relevant statistical operator, yields are calculated taking excited states and continuum correlations into account, in accordance with the virial expansion of the equation of state. Clusters with mass number $A\le 10$ are well described using the nonequilibrium generalizations of temperature and chemical potentials. Improving the virial expansion, in-medium effects may become of importance in determining the contribution of weakly bound states and continuum correlations to the intrinsic partition function. Yields of larger clusters, which fail to reach this quasiequilibrium form of the relevant distribution, are described by nucleation kinetics, and a saddle-to-scission relaxation time of about 7000 fm/c is inferred. Light-charged particle emission, described by reaction kinetics and virial expansions, may therefore be regarded as a very important tool to probe the nonequilibrium time evolution of actinide nuclei during fission.

The ${}^8\mathrm{Li}+{}^{58}\mathrm{Ni}$ collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Quasielastic angular distributions and the singles ${}^7\mathrm{Li}$ angular and energy distributions are presented. Coupled-reaction channels (CRC) calculations, which include the coupling of the elastic channel to ${}^{59}\mathrm{Ni}={}^{58}\mathrm{Ni}+n$ states above and below the neutron threshold, provide a simultaneous description of the quasielastic and transfer distributions and evidence the strong effect of the one-neutron transfer/breakup channels on the quasielastic scattering. The ${}^7\mathrm{Li}$ angular and energy distributions have been also successfully analyzed combining the continuum discretized coupled channels (CDCC) method, for the elastic breakup, and the IAV model of Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)], for the nonelastic breakup. These calculations indicate that most of the ${}^7\mathrm{Li}$ yields are due to nonelastic breakup contributions (transfer), whereas elastic breakup plays a minor role.