The magnitude of fluctuations between charged and neutral kaons measured by the ALICE Collaboration in heavy-ion collisions at the LHC exceeds conventional explanation. Here it is shown that if the scalar condensate, which is typically associated with chiral symmetry, is accompanied by an $\mathrm{isospin}=1$ field, then the combination can produce large fluctuations where $\langle \overline{u}u\rangle \ne \langle \overline{d}d\rangle$. Hadronizing strange and antistrange quarks might then strongly fluctuate between charged ($u\overline{s}$ or $s\overline{u}$) and neutral ($d\overline{s}$ or $s\overline{d}$) kaons.

We study the space-time evolution of electromagnetic fields along with the azimuthal fluctuations of these fields and their correlation with the initial matter geometry specified by the participant plane in the presence of finite electric $\left(\sigma \right)$ and chiral magnetic $\left({\sigma }_{\chi }\right)$ conductivities in $\mathrm{Ru}+\mathrm{Ru}$ and $\mathrm{Zr}+\mathrm{Zr}$ collisions at $\sqrt{s_{NN}}=200$ GeV. We observe the partially asymmetric behavior of the spatial distributions of the electric and magnetic fields in a conducting medium when compared to the Lienard-Wiechert (L-W) solutions, and deceleration of the decay of the fields is observed in both isobar collisions. While studying the correlation between the magnetic field direction and the participant plane, we see the sizeable suppression of the correlation in the presence of finite conductivities when compared to the L-W case, reflecting the importance of taking into account the medium properties such as conductivities while calculating the magnetic field induced observable quantities.

A low-energy enhancement (LEE), which was observed experimentally in the $\gamma$-ray strength function ($\gamma \mathrm{SF}$) describing the decay of compound nuclei, would have profound effects on $r$-process nucleosynthesis if it persists in heavy neutron-rich nuclei. The LEE was shown to be a feature of the magnetic dipole ($M1)$ strength function in configuration-interaction shell-model calculations in medium-mass nuclei. However, its existence in heavy open-shell nuclei remains an open question. Here, using a combination of many-body methods, we identify a LEE in the $M1\gamma \mathrm{SFs}$ of heavy samarium nuclei. In particular, we use the static-path plus random-phase approximation ($\text{SPA}+\text{RPA}$), which includes static and small-amplitude quantal fluctuations beyond the mean field. Using the $\text{SPA}+\text{RPA}$ strength as a prior, we apply the maximum-entropy method to obtain finite-temperature $M1\gamma \mathrm{SFs}$ from exact imaginary-time response functions calculated with the shell-model Monte Carlo method. We find that the slope of the LEE in samarium isotopes is roughly independent of the average initial energy over a wide range below the neutron separation energy. As the neutron number increases, strength transfers to a low-energy excitation, which we interpret as the scissors mode built on top of excited states.

Nuclear entanglement is a flagship in the interdisciplinary direction of nuclear physics and quantum information science. Spin entanglement, a special kind of nuclear entanglement, is ubiquitous in nuclear structures and dynamics. Based on the idea of quantum state tomography, the problem of experimental determination of spin entanglement of two-nucleon pure states is studied directly within the scope of nuclear physics. It is shown that the amount of spin entanglement can be obtained by measuring three spin polarizations of one nucleon in polarization experiments. The errors from imperfect preparation of nucleon pairs are also analyzed. This work not only complements the existing literature of nuclear entanglement but also provides new opportunities for nuclear physics with polarized particles.

A series of relativistic one-boson-exchange potentials for a two-nucleon system, denoted as $\mathrm{OBEP}\mathrm{\Lambda }$, is constructed with a momentum cutoff $\mathrm{\Lambda }$ ranging from $\infty$ to 2 ${\mathrm{fm}}^{-1}$. These potentials are developed by simultaneous fitting to nucleon-nucleon ($NN$) scattering phase shifts, low-energy scattering length, effective range, and the binding energy of the deuteron. The momentum-space matrix elements of the low-momentum $\mathrm{OBEP}\mathrm{\Lambda }$ ($\mathrm{\Lambda }⩽3{\mathrm{fm}}^{-1}$) demonstrate consistency with the universal behaviors observed in other realistic $NN$ potentials evolved by renormalization group methods. These $\mathrm{OBEP}\mathrm{\Lambda }\mathrm{s}$ are applied to calculate the equation of state of symmetric nuclear matter (SNM) within either the nonrelativistic (NR) Brueckner-Hartree-Fock (BHF) or relativistic Brueckner-Hartree-Fock (RBHF) frameworks. The results show that the saturation properties of SNM are reproduced qualitatively from the RBHF calculation, but not from the NR-BHF calculation. This study highlights the relativistic mechanism in explaining the saturation properties of nuclear matter. The remaining discrepancy in reproducing empirical saturation properties in the RBHF calculation using the $\mathrm{OBEP}\mathrm{\Lambda }\mathrm{s}$ signals the necessity of including three-nucleon correlations or genuine three-nucleon forces.

We have generalized the four-dimensional Langevin approach used in our previous works for the description of the fission process to five dimensions by considering the neck parameter $\epsilon$ in the two-center shell model shape parametrization as an independent dynamical variable. The calculated results for the mass distribution of fission fragments are in better agreement with the available experimental data. In particular, the transition from mass-symmetric to mass-asymmetric fission via the triple-humped distribution in fission of thorium isotopes is well reproduced.

Missing mass spectroscopy of the unbound ${}^8\mathrm{C}$ nucleus was performed by the one-neutron transfer ${}^9\mathrm{C}(p,d){}^8\mathrm{C}$ reaction at 55 MeV/nucleon. Besides the known ground state, two new resonant states were observed, the first at an excitation energy of 3.40(25) MeV with a width of 3.0(5) MeV, the second at 18.6(5) MeV with a width of 3.9(11) MeV. Spin and parity $J^{\pi }=2^{+}$ were assigned to the first resonance from the distorted-wave Born approximation analysis of the experimental differential cross section. The excitation energy of the $2^{+}$ resonance in ${}^8\mathrm{C}$ supports the persistence of the subshell closure at the semimagic number $Z$ = 6, as is the case for $N$ = 6. The mirror energy difference relative to the $2^{+}$ state in ${}^8\mathrm{He}, \mathrm{\Delta }{E}_{\mathrm{x}}=-0.14$(25) MeV, is compatible with zero. Both states represent resonances in the continuum, unbound by about 1.4 and 6.9 MeV, respectively, above the particle thresholds. A simple theoretical model emphasizes the difference in unboundedness to account for a symmetry in mirror energies. This unique system is expected to provide a salient test of theoretical models, which include the treatment of the continuum.

We discuss how heavy quark dynamics is affected by the critical fluctuations near the QCD critical point at finite temperature and density. We find that the heavy quark momentum diffusion constant scales as $\kappa \propto {\xi }^{z-3-\eta }$. In the model $\mathrm{H}$ scenario, which is widely accepted for critical dynamics, the exponents are known as $z\simeq 3\text{and}\eta \approx 0.04$ and the critical singularity of $\kappa$ is not significant if present. In the model $\mathrm{B}$ scenario, $z\simeq 4$ and $\kappa \propto \xi$ is singular near the critical point.

Background: The appearance of the pairing condensate is an essential feature of many-fermion systems. There are two possible types of pairing: spin-singlet and spin-triplet. However, an open question remains as to whether the spin-triplet pairing condensate emerges in finite nuclei.

Purpose: The aim of this work is to examine the coexistence of the spin-singlet and spin-triplet like-particle pairing condensates in nuclei. We also discuss the dependence on the type of pairing functional.

Method: The Hartree-Fock-Bogoliubov calculations with a Skyrme $+$ local-pair energy-density functional (EDF) are performed to investigate the pairing condensate in the spherical ground states of Ca and Sn isotopes.

Results: The spin-singlet pair EDF induces not only the spin-singlet but also the spin-triplet pairing condensates due to a strong spin-orbit splitting. By discarding the spin-orbit EDF, only the spin-singlet pairing condensate appears. The spin-triplet pair EDF, however, induces the spin-orbit splitting and accordingly the spin-singlet pairing condensate.

Conclusions: The spin-orbit splitting plays an essential role in the coexistence of the spin-singlet and spin-triplet pairing condensates in nuclei.

We use a microscopic cluster model to investigate the ${}^{15}\mathrm{C}$ nucleus. Two variants are considered: a two-cluster ${}^{14}\mathrm{C}+n$ description and a three-cluster ${}^{13}\mathrm{C}+n+n$ approach. We show that ${}^{15}\mathrm{C}$ bound-state energies converge to similar values, provided that the number of ${}^{14}\mathrm{C}$ states is sufficient. We also study negative-parity states, and show that the three-cluster model is more appropriate. With the same nucleon-nucleon interaction, we analyze the ${}^{15}\mathrm{F}$ spectrum, where all known states are unbound.

The hexadecapole deformation, as well as the quadrupole one, influences the low-lying states of finite nuclei. The hexadecapole correlations are often overshadowed by the large quadrupole effects, and hence have not been much investigated. Here we address the relevance of hexadecapole deformations in the calculations of low-energy collective states of heavy nuclei, by using the theoretical framework of the self-consistent mean-field method and the interacting-boson approximation. The interacting-boson Hamiltonian that explicitly includes the quadrupole and hexadecapole collective degrees of freedom is specified by a choice of the energy density functional and pairing interaction. In an illustrative application to axially deformed Gd isotopes, it is shown that the inclusion of the hexadecapole degree of freedom does not affect most of the low-spin and low-lying states qualitatively, but that has notable effects in that it significantly improves the description of high-spin states of the ground-state bands of nearly spherical vibrational nuclei and gives rise to $K^{\pi }=4^{+}$ bands exhibiting strong $E4$ transitions in strongly deformed nuclei.

We investigate the nuclear symmetry energy and neutron star properties using a Bayesian analysis based on constraints from different chiral effective field theory calculations using new energy density functionals that allow for large variations at high densities. Constraints at high densities are included from observations of GW170817 and from NICER. In particular, we show that both NICER analyses lead to very similar posterior results for the symmetry energy and neutron star properties when folded into our equation-of-state framework. Using the posteriors, we provide results for the symmetry energy and the slope parameter, as well as for the proton fraction, the speed of sound, and the central density in neutron stars. Moreover, we explore correlations of neutron star radii with the pressure and the speed of sound in neutron stars. Our 95% credibility ranges for the symmetry energy $S_v$, the slope parameter $L$, and the radius of a $1.4M_{\odot }$ neutron star, $R_{1.4}$, are $S_v=(30.6–33.9)\mathrm{MeV}, L=(43.7–70.0)\mathrm{MeV}$, and $R_{1.4}=(11.6–13.2)\mathrm{km}$. Our analysis for the proton fraction shows that larger and/or heavier neutron stars are more likely to cool rapidly via the direct Urca process. Within our equation-of-state framework a maximum mass of neutron stars $M_{\max }>2.1M_{\odot }$ indicates that the speed of sound needs to exceed the conformal limit.

Neutron stars offer a great opportunity to study highly compressed hadronic matter experimentally and theoretically. However, the so-called hyperon-puzzle arises at neutron star densities. The hyperon coexistence with other particles in compressed matter softens the equation of state and many widely accepted models fail to reproduce precise observations of large neutron star masses. Here, we propose a mechanism to retain the stiffness of the high density state with hyperons by considering the explicit momentum dependence of their in-medium potentials. Our approach modifies conventional strangeness threshold conditions and generates threshold effects on hyperons in high-density matter. We demonstrate these effects within the nonlinear derivative model, which incorporates baryon momentum-dependent fields based on empirical and microscopic studies. It turns out that even soft momentum-dependent strangeness fields do prohibit their populations in neutron star matter. The generic momentum dependence of strangeness potentials, as modeled by the nonlinear derivative approach, is crucial for resolving the long-standing hyperon-puzzle in neutron stars.

Simulations of the $\mathrm{\Lambda }$-hyperon and light-hypernuclei production in Au+Au collisions at $\sqrt{s_{NN}}=3$ GeV were performed within the updated three-fluid hydrodynamics-based event simulator extended by UrQMD (ultrarelativistic quantum molecular dynamics) final state interactions (THESEUS). The light (hyper)nuclei are treated thermodynamically, i.e., they are considered on an equal basis with hadrons. The only additional parameter is related to the late freeze-out that imitates the afterburner stage for the light (hyper)nuclei because UrQMD is not able to dynamically treat them. The calculation of hypernuclei production is the same as that of light nuclei. The hypernuclei results are compared with recent STAR data. It is found that the calculated midrapidity ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}/\mathrm{\Lambda }$ ratio falls within the error bars of the experimental point. It is remarkable that the large difference between the $t/p$ and ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}/\mathrm{\Lambda }$ ratios is reproduced without any additional parameters. Rapidity distributions of ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}/\mathrm{\Lambda }$ and ${}_{\mathrm{\Lambda }}{}^4\mathrm{He}/\mathrm{\Lambda }$ ratios are predicted. Midrapidity mean transverse momenta of protons, $\mathrm{\Lambda }$'s and light (hyper)nuclei in central collisions agree well with the data. The calculated directed flow also reasonably well reproduces of the data.

The polarization of real photons emitted from early-time heavy-ion collisions is calculated, concentrating on the contribution from bremsstrahlung and quark-antiquark annihilation processes at leading order in the strong coupling. The effect of an initial momentum space anisotropy of the parton distribution is evaluated using a model for the nonequilibrium scattering kernel for momentum broadening. The effect on the photon polarization is reported for different degrees of anisotropy. The real photons emitted early during in-medium interactions will be dominantly polarized along the beam axis.

In the present paper, negative-parity bands based on the $\nu h_{11/2}$ configuration in ${}^{125}\mathrm{Xe}$ have been revisited. This nucleus was populated through the reaction ${}^{82}\mathrm{Se}({}^{48}\mathrm{Ca},5n){}^{125}\mathrm{Xe}$ at a beam energy of 205 MeV and the corresponding $\gamma$ rays were observed using the Gammasphere spectrometer. Evidence for first and second phonon wobbling excitations has been established by measurements of directional correlation ratios and angular distributions of the involved $\gamma$ rays. The observed wobbling energy of the bands involved were compared with the recently published results obtained within the framework of triaxial projected shell-model calculations.

Simultaneous analyses are performed of cross-section data for elastic scattering, fusion, Coulomb breakup, and other direct yields for the ${}^6\mathrm{He}+{}^{209}\mathrm{Bi}$ system at near Coulomb-barrier energies. The bare and dynamical polarization potentials are constructed microscopically from the structure of the colliding nuclei and they reproduce all the data well with only two adjustable parameters. This method of calculation can be successfully applied to the reactions of weakly bound and exotic projectiles with heavy targets.

Faddeev calculations of hypertriton (${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$) separation energy are carried out, incorporating all next-to-next-to-leading-order $\mathrm{\Lambda }NN$ three-body forces (3BFs) in chiral effective field theory: $2\pi$ exchange, $1\pi$ exchange, and contact interactions. The $1\pi$ exchange and contact interactions are rewritten in a form suitable for evaluating partial-wave matrix elements. The $\mathrm{\Lambda }$-deuteron folding potentials constructed from these 3BFs are evaluated to demonstrate their contributions to ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$. The $1\pi$ exchange interaction provides an attractive effect in which the $d$-state component of the deuteron wave function plays an important role. The attractive contribution tends to cancel the repulsive ones from the $2\pi$ exchange and contact 3BFs. Faddeev calculations show that the net effect of the 3BFs to the ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ separation energy is small in a range between $-5$ to $+20$ keV, depending on the $NN$ interaction used. Although these results are based on speculative low-energy constants, they can serve as a reference for further investigations.