Neutrino processes are important in the modeling of supernova explosions, proto-neutron star evolution, and binary neutron star mergers. We study neutrino production and absorption in proto-neutron star and supernova matter and direct Urca neutrino emission of neutron star matter in the framework of the random phase approximation (RPA). As interactions, we employ the recent extended Skyrme parametrization Sky3s whose effective masses and spin-dependent terms were adjusted to microscopic calculations, and the SLy4 parametrization that was used in previous calculations of neutrino rates. The rates obtained for Sky3s differ from those for SLy4 by up to one order of magnitude for some processes and energy regions. We also determine the electron, muon, and proton fractions that lead to a stationary composition of matter for a density above the direct Urca threshold, and find that with Sky3s the standard $\beta$ equilibrium condition is not as badly violated at finite temperature as predicted in the literature. There are also minor differences between the full RPA and the common Landau approximation, but they are probably not significant for astrophysical simulations. We conclude that it would be worthwhile to repeat the calculation of neutrino rates for the use in astrophysical simulations, and the corresponding simulations, with several and better constrained interactions than SLy4, such as Sky3s.

High-spin states of ${}^{125}\mathrm{I}$ have been populated using the ${}^{122}\mathrm{Sn}({}^7\mathrm{Li},4n){}^{125}\mathrm{I}$ reaction at a beam energy of 44 MeV. Four three-quasiparticle rotational bands originating from neutron alignment were observed. A pair of nearly degenerate positive-parity doublet bands is assigned the $\pi g_{7/2}\otimes \nu h_{11/2}^2$ configuration and proposed as candidate chiral doublet bands. Another positive-parity band and a negative-parity band are assigned the $\pi g_{7/2}\otimes \nu {(g_{7/2}/d_{5/2})}^2$ and $\pi g_{7/2}\otimes \nu h_{11/2}(g_{7/2}/d_{5/2})$ configurations, respectively. These interpretations are supported by the adiabatic and configuration-fixed constrained triaxial relativistic-mean-field and multiparticle plus rotor model calculations.

In this study, we investigate the impact of the effective nucleon mass and the existence of the dineutron and the tetraneutron on the thermodynamic properties and nuclear composition by constructing new equations of state. Our results indicate that the model with a larger effective nucleon mass slightly alters the nuclear composition in neutron-rich environments primarily due to differences in the symmetry energy: the mass fractions of unbound neutrons, protons, and heavy nuclei increase. The impact on the thermodynamic properties is negligible, except for the chemical potentials. On the other hand, multineutron states become prominent at high densities in neutron-rich environments, leading to a substantial reduction in the unbound neutron fraction. This depletion lowers the chemical potential of unbound neutrons, which in turn reduces the abundance of neutron-rich nuclei. Consequently, the number of unbound protons increases, leading to a corresponding rise in proton chemical potential. These shifts in chemical potentials promote the formation of heavy nuclei with larger mass and proton numbers. Ultimately, this compositional shift results in a lower free energy, primarily driven by the emergence of these heavy nuclei.

Per-trigger yields of ${\pi }^0\text{−}\mathrm{hadron}$ correlations were measured in semicentral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\text{TeV}$ in ALICE at the CERN Large Hadron Collider. The reconstructed ${\pi }^0\to \gamma \gamma$, with a transverse momentum of $11\mathrm{GeV}/c<p_{\mathrm{T}}\left({\pi }^0\right)<14\mathrm{GeV}/c$, is used as the trigger particle to calculate yields of associated charged particles on the near- and away-side. The photons are reconstructed using the ALICE Electromagnetic Calorimeter, and the charged particles are measured in the ALICE central barrel within a pseudorapidity range of $\left|\eta \right|<0.8$. The yields are reported relative to the orientation of the ${\pi }^0$ with the second-order event plane and are background subtracted using the reaction-plane fit method. The data give an indication of a suppression of the associated charged-particle yields near $p_{\mathrm{T}}\approx 2\mathrm{GeV}/c$ when comparing out-of-plane to in-plane trigger particles. At associated charged-particle $p_{\mathrm{T}}>3$ GeV/$c$, no significant event-plane dependence is observed within uncertainties. The results are compared with predictions from the JEWEL model, which implements jet energy loss in an expanding medium. JEWEL predicts no significant modification of either the near- or away-side associated yields, independent of whether medium recoils are included. The observed behavior may indicate the presence of additional energy-loss mechanisms beyond those governed by path-length dependence.

Background: The $N=80$ isotones offer an important opportunity for studying nuclear structure evolution and the interplay between single-particle motion and collective behavior near the $N=82$ shell closure. Although the nuclear shell model is a powerful and predictive framework, progress for the open-shell nuclei has been limited by the rapidly increasing configuration-space dimensions and the lack of a reliable effective interaction.

Purpose: To construct a feasible shell-model Hamiltonian capable of describing the $N=80$ even-even isotonic chain with $Z=50–74$, and to investigate their underlying low-lying configurations.

Methods: Full-configuration-interaction shell-model calculations are performed in a model space that includes the proton and neutron orbitals $0g_{7/2}, 1d_{5/2}, 1d_{3/2}, 2s_{1/2}$, and $0h_{11/2}$. The effective interaction is derived by optimizing the monopole and multipole components of the realistic interactions, reducing the number of independent parameters to eight via the principal component analysis approach. Further analysis is carried out using the nucleon-pair approximation of the shell model.

Results: The calculation reproduces excitation energies and electromagnetic properties for known $N=80$ isotones and provides predictions for ${}^{150}\mathrm{Yb}, {}^{152}\mathrm{Hf}$, and ${}^{154}\mathrm{W}$ near the proton drip line, including a level inversion between the yrast ${18}^{+}$ and ${20}^{+}$ states in ${}^{154}\mathrm{W}$. It further reveals a systematic evolution of the low-lying structures with increasing proton number.

Conclusions: The $N=80$ isotones exhibit coexistence of multiple configurations: the yrast $0^{+}–4^{+}$ states are (generalized-)seniority-dominated for lower-$Z$ nuclei, becoming increasingly vibrational-like with growing valence proton number, while the yrast $6^{+}–{10}^{+}$ states undergo transitions among neutron seniority-2, proton seniority-2, and proton-neutron coupled configurations along the isotonic chain, driven by proton-neutron interactions and the evolution of the proton Fermi surface. The analysis of the predicted level inversion in ${}^{154}\mathrm{W}$ highlights the essential role of the isoscalar spin-aligned proton-neutron correlation.

Low-spin excitations of ${}^{91}\mathrm{Zr}$ and ${}^{93}\mathrm{Zr}$ nuclei, populated in the ($n,\gamma$) cold-neutron-capture reactions, have been studied using the highly efficient array EXILL, at the Institute-Laue-Langevin (ILL), Grenoble. 14 new excited levels and 36 new $\gamma$ transitions, including 16 primary decays, have been found in the two nuclei. High accuracy of transition energies obtained in the present work allowed to improve neutron binding energies of both nuclei determined in this work at 7194.06(8) keV in ${}^{91}\mathrm{Zr}$ and 6734.92(5) keV in ${}^{93}\mathrm{Zr}$. The accurate $S_n$ values helped to improve masses of ${}^{91,93,95,97}\mathrm{Zr}$ isotopes. Significant lowering of the $3/2_1^{+}$ excitation in ${}^{93}\mathrm{Zr}$ is interpreted as due to anomalous coupling of the odd neutron in the $\nu d_{5/2}$ shell to the $2_1^{+}$ vibrations of adjacent Zr cores.

Knowing that stable Zr isotopes near the double-magic ${}^{90}\mathrm{Zr}$ nucleus remain spherical, we construct a dispersive optical potential to describe nucleon scattering on zirconium isotopes by introducing linear dependence on mass number $A$ into selected geometric parameters of the optical potential for ${}^{90}\mathrm{Zr}$. Nonlocality of the real potential and isotopic shell gaps are also considered. Excellent agreement with measurements is shown for nucleon-nucleus elastic scattering data of the zirconium isotopes ${}^{91,92,94,96}\mathrm{Zr}$ and also of the natural zirconium.

The centrality dependence of strange ($K_S^0$, $\mathrm{\Lambda }+\overline{\mathrm{\Lambda }}$) and multistrange (${\mathrm{\Xi }}^{-}+{\overline{\mathrm{\Xi }}}^{+}$, ${\mathrm{\Omega }}^{-}+{\overline{\mathrm{\Omega }}}^{+}$) hadron production is measured by ALICE in the Large Hadron Collider (LHC) lead-lead (Pb-Pb) collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=5.02$ TeV, using the full dataset collected during the LHC Run 2 campaign in the years 2015 and 2018. This is the largest heavy-ion dataset analyzed to date at the LHC, and it allows for the extraction of transverse momentum ($p_T$) spectra and $p_T$-integrated yields with unprecedented precision, over a broad range of charged particle multiplicity densities (${\langle \mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta \rangle }_{\left|\eta \right|<0.5}$), probing regions where smaller collision system (pp and $p$-Pb) results are also available. The $p_T$ spectra evolve with centrality, featuring higher $\langle p_T\rangle$ in central events for all particles. The $\mathrm{\Lambda }/K_S^0$ ratio exhibits the distinctive baryon-to-meson enhancement in the intermediate $p_T$ region, with a maximum which is shifted to larger $p_T$ for more central collisions. The hadron-to-pion yield ratios are presented as a function of ${\langle \mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta \rangle }_{\left|\eta \right|<0.5}$ and compared to results from different collision systems and energies. A smooth connection from pp to Pb-Pb is observed, thus demonstrating that collision system or energy do not play a role in the multiplicity evolution of this observable. The previously reported enhancement of strangeness production in the multiplicity range probed in pp and $p$-Pb collisions saturates in the multiplicity range of Pb-Pb data. These results constitute a key test bench for theoretical models and a first comparison to the EPOS 4 generator is presented.

The exponential growth of the model space often hinders accurate configuration interaction shell model (CISM) calculations for nuclear structure. To address this, we develop an adaptive CISM (ACISM) approach, adapted from the adaptive configuration interaction (ACI) approach used in quantum chemistry. We first apply ACISM to ground-state calculations of $sd$- and $pf$-shell nuclei. The results show that the ground-state energy converges controllably to the full CISM results as the truncation parameter $\sigma$ is decreased. Furthermore, $\mathit{pf}$-shell calculations demonstrate that ACISM can reduce the model space by at least two orders of magnitude while maintaining energy errors within a few hundred keV, highlighting the method's potential for large-scale model-space computations. The systematic dependence on $\sigma$ enables reliable extrapolation toward the full CISM limit. Then, using a state-specific, orthogonality-constrained extension of ACISM, we obtain a stable low-lying spectrum for ${}^{52}\mathrm{Fe}$ across a wide range of $\sigma$. Our results demonstrate robust spectral convergence even when the model-space dimension is truncated by approximately two orders of magnitude. Finally, the calculations of the expectation value of the square of total angular momentum of eigenstates indicate that ACISM exhibits a relatively small degree of breaking of angular momentum symmetry.

Background: Hypernuclear physics studies baryon interactions and the structure of exotic atomic nuclei, where strangeness plays a key role in dense matter. High-resolution $\gamma$-ray spectroscopy (e.g., Hyperball at BNL/KEK) and upcoming facilities (J-PARC and JLab) have provided precise data on $p$-shell hypernuclei, constraining $YN$ potentials.

Purpose: We applied the Gamow shell model to $p$-shell hypernuclei to systematically investigate the role of the $\mathrm{\Lambda }N$ interaction and its components and how it affects the mean field of nucleons.

Method: The Gamow shell model extends the standard shell model by replacing the harmonic oscillator basis with the Berggren ensemble, treating bound, resonant, and continuum states on equal footing. The effective Hamiltonian includes Woods-Saxon core potentials and two-body interactions (central, spin-orbit, tensor) optimized to experimental data.

Results: Our calculations reproduce and predict binding energies, excitation spectra, and densities for hypernuclei from ${}_{\mathrm{\Lambda }}^5\mathrm{He}$ to ${}_{\mathrm{\Lambda }}^{16}\mathrm{O}$ using the same $\mathrm{\Lambda }N$ interaction. The tensor force significantly impacts excited-state splittings in bound systems, while its effect is suppressed in unbound cases due to the continuum coupling.

Conclusions: The Gamow shell model provides a unified framework for hypernuclei, capturing the interplay between bound, resonant, and continuum states. This work lays the foundation for extending the model to heavier and multistrange systems.

Many-body perturbation theory provides a powerful framework to study the ground state and thermodynamic properties of nuclear matter as well as associated single-particle potentials and response functions within a systematic order-by-order expansion. However, computational challenges can emerge beyond the lowest orders of perturbation theory, especially when computing both single-particle potentials and response functions, which in general are complex-valued and require Cauchy principal value calculations of high-dimensional integrals. We demonstrate that normalizing flows are suitable for Monte Carlo importance sampling of both regular and irregular functions appearing in nuclear many-body calculations. Normalizing flows are a class of machine-learning models that can be used to build and sample from complicated distributions through a bijective mapping from a simple base distribution. Furthermore, a well-trained model for a certain target integrand can be efficiently transferred to calculate related integrals with varying physical conditions. These features can enable more efficient tabulations of nuclear physics inputs to numerical simulations of supernovae and neutron-star mergers across varying physical conditions and nuclear force models.

Understanding nuclear forces, infinite nuclear matter, and finite nuclei within a unified framework has remained a central challenge in nuclear physics for decades. While most ab initio studies employ nonrelativistic Schrödinger-equation frameworks, this work offers a relativistic perspective. Using a leading-order relativistic chiral interaction, we study medium-mass nuclei (Ca, Ni, Zr, Sn) via the relativistic Brueckner-Hartree-Fock theory. Systematic uncertainties from regulator cutoffs and interaction parameters are analyzed. The binding energies and charge radii of medium-mass nuclei agree reasonably well with experimental data, significantly improving the “Coester line”. The charge density distributions also agree well with the data, highlighting the connection to a consistent reproduction of nuclear matter saturation. These results demonstrate that the relativistic approach, employing a leading-order chiral force with only four low-energy constants and no three-nucleon forces, can capture the most important dynamics and offer a complementary pathway to address longstanding challenges in nuclear ab initio studies.

Background: Fragment shell effects are central to the formation of spontaneous-fission (SF) mass yields. However, it remains unclear which configurations favored by fragment shell effects are dynamically selected and ultimately appear as peaks in the SF yields.

Purpose: To clarify, by comparing ${}^{240}\mathrm{Pu}, {}^{232}\mathrm{Th}$, and ${}^{264}\mathrm{Fm}$, how the potential-energy surface (PES) topology and the fission dynamics in the classically allowed region select the scission configurations in which fragment shell stabilization is reflected in the SF yield peaks.

Method: A two-step microscopic framework is employed. The PES and collective inertia are obtained from constrained Hartree–Fock–Bogoliubov calculations. The first step, from the inner to the outer turning points, is treated within the Wentzel–Kramers–Brillouin approximation along the least-action path. The second step, from the outer turning points to scission in the classically allowed region, is described by Langevin dynamics. Fragment shell effects are analyzed through fragment PES and smoothed level density indicators evaluated for representative even-even fragment pairs selected from the Langevin scission configurations.

Results: The calculated yields display a two-component asymmetric pattern in ${}^{240}\mathrm{Pu}$, a less distinctly separated asymmetric pattern in ${}^{232}\mathrm{Th}$, and a symmetric peak in ${}^{264}\mathrm{Fm}$. The fragment shell analysis shows that the larger yield components coincide with a coherent overlap among dynamically populated scission configurations, favorable fragment PES regions, and regions of low neutron and/or proton level density near the Fermi surface. This overlap is most evident in the dominant asymmetric components of ${}^{240}\mathrm{Pu}$ and ${}^{232}\mathrm{Th}$ and in the symmetric component of ${}^{264}\mathrm{Fm}$, whereas the subdominant components show weaker or more diffuse overlap.

Conclusion: SF yields reflect shell-favored fragment configurations that are made accessible by the PES topology and populated by the Langevin dynamics. Enhanced yields then arise in shell-stabilized channels, where shell gaps provide additional binding and favor the fragment configurations energetically. Proton shell effects play a key role in heavy and light fragments, while neutron shell effects provide additional stabilization.

The generator coordinate method (GCM) was introduced in nuclear physics by Wheeler and independently by Peierls and their collaborators in 1950s and it is still one of the most used approximations for treating nuclear large-amplitude collective motion. GCM was inspired by similar methods introduced in molecular and condensed-matter physics in the late 1920s, after the Schrödinger equation became the tool of choice to describe quantum phenomena. The interest in the 1983 extension of GCM suggested by Reinhard, Cusson, and Goeke, which includes the internal excitations (absent in the initial GCM formulation), was revived in recent years. Unfortunately, this newer version of the time-dependent GCM framework has flaws that prevent it from describing correctly many anticipated features, in particular interference and entanglement, which can play an important role in fission and many-nucleon transfer reactions. I present here an alternative formulation, the enhanced GCM (eGCM), which is free of the difficulties encountered in previous GCM implementations and which is relevant for fission and many-nucleon transfer in heavy-ion reactions, and which can be used in either static or time-dependent eGCM formulations. In the eGCM framework, the corresponding many-body wave functions have a much more complex structure, and this framework is equivalent to a configuration-interaction approach in the continuum for nuclear reactions. The eGCM is aimed at being used in the microscopic description of heavy-ion reactions and fission in particular. The eGCM framework opens the possibility to evaluate time-dependent lower bounds on the entropy in nuclear reactions and induced fission in particular, and thus on the evolution toward “thermalization” or equilibration. The eGCM framework is well suited to extract in a microscopic approach the induced fission cross sections, which are notoriously difficult to model.

We propose a generic empirical formula for total inelastic cross sections for various target nuclei scattered by a proton at different energies, which is applicable over a wide range of energy from $15\mathrm{MeV}$ to $1\mathrm{TeV}$. The proposed model is parameterized based on the fitting of extensively studied experimental cross-section data for the aluminium and carbon nuclei targets, considering factorization over high-energy and low-energy regimes. The parameters in high-energy formula are determined by the fitting of the high-energy saturation value of the inelastic scattering cross-section data with mass numbers. The universality of the empirical formula is investigated by comparing the model prediction with the experimental data of inelastic proton-nucleus scattering over a wide range from light elements such as deuterium to heavy elements such as uranium. A detailed comparison with the existing models and GEANT4 simulation is also presented.

The effect of $\alpha$ clustering of heavy fragment in scission configurations on the mass, charge, neutron multiplicity, and total kinetic energy distributions of fragments of spontaneous fission of ${}^{256,258}\mathrm{Fm}$ is simultaneously considered. Predictions for some observables are presented that may be experimentally verified.

We investigate the elliptic-flow splitting between prompt $D^0$ and $D_s^{+}$ mesons within a heavy-quark transport framework with sequential hadronization, in which $D_s^{+}$ forms at $1.2T_c$ and $D^0$ at $T_c$. We present model calculations for the $p_T$-differential $v_2$ and predictions for the $D_s^{+}/D^0$ yield ratio in O-O $0–20\%$ collisions at $\sqrt{s_{NN}}=5.36$ TeV, where preliminary ALICE data are available. The sequential scenario reproduces the observed $v_2\left(D^0\right)>v_2\left(D_s^{+}\right)$ ordering and predicts an enhanced $D_s^{+}/D^0$ ratio at low $p_T$, whereas a simultaneous baseline yields the opposite ordering. Decomposing the hadronic splitting into its partonic components, we show that the $v_2$ ordering is driven by the late-stage flow accumulated by $D^0$-parent charm quarks during the $1.2T_c\to T_c$ interval, with hadronic rescattering essential to preserve the signal in small systems. A systematic scan across nine collision configurations spanning O-O and Pb-Pb centralities reveals a universal linear scaling between the hadronic splitting and the partonic flow increment accumulated during this window. This establishes the $D^0–D_s^{+}$ flow splitting as a hadronization chronometer of the QGP at $\sqrt{s_{NN}}=5.36$ TeV.

Jet substructure studies at the CERN Large Hadron Collider have been used to constrain parton distribution functions, test perturbative quantum chromodynamics, measure the strong-coupling constant, and probe the properties of the quark-gluon plasma. We extend these studies to lower collision energies at the BNL Relativistic Heavy Ion Collider (RHIC) and present a feasibility and strategy study for the sPHENIX experiment. In this work, we perform a $\mathrm{PYTHIA8}$ based Monte Carlo study of jet substructure in $p+p$ collisions at $\sqrt{s}=200$ GeV with selection criteria adapted for a realistic measurement at sPHENIX. We consider jet substructure observables such as jet angularities and the primary Lund plane projection. In particular, we quantify the discriminating power of jet angularities for quark/gluon and light versus heavy flavor jets, and demonstrate how these observables can serve as experimentally accessible proxies for flavor separation at RHIC. We further show that the primary Lund plane exhibits a characteristic suppression pattern consistent with the dead cone effect for heavy quarks, and outline a concrete measurement strategy at sPHENIX based on a combination of heavy-flavor jet tagging and differential substructure observables.

The nuclear drip line plays a crucial role in determining the composition of matter under extreme astrophysical conditions. In core-collapse supernovae and neutron-star crusts, matter is driven far from saturation density and nuclear stability; nuclei coexist with a sea of free neutrons, an effect that is present even at zero temperature in neutron-star crusts and becomes more pronounced in the hotter, neutron-rich supernova environment. This makes a careful treatment of drip-line physics essential for a realistic description of the equation of state and composition. In this work, the influence of the nuclear drip line on the baryonic composition of supernova matter is investigated within the framework of nuclear statistical equilibrium. The composition is evaluated in terms of free nucleons, light clusters, and heavy nuclei at finite temperature and global sub-saturation densities. The results indicate that, at low proton fractions and higher densities, the inclusion of nuclei beyond the drip line enhances the formation of extremely neutron-rich light clusters, leading to a significant reduction in the free-neutron density and the charge fraction of heavy nuclei. These findings demonstrate that drip-line physics has a significant impact on the composition of supernova matter and should be carefully incorporated in supernova modeling and nucleosynthesis studies.