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.

Charge radii differences of mirror partner nuclei provide an alternative probe to pin down the interaction components in asymmetric nuclear matter. In this work, the differences in the charge radii of almost spherical mirror-paired nuclei ${}^{54}\mathrm{Ni}\text{−}{}^{54}\mathrm{Fe}$ and ${}^{36}\mathrm{Ca}\text{−}{}^{36}\mathrm{S}$ are used to constrain the magnitude of tensor terms in the Skyrme interactions. The calculated results suggest that a linear correlation can be found between the difference of charge radii of mirror partner nuclei and the adopted strengths of the triplet-odd and triplet-even tensor components. In addition, it suggests that charge radii differences of mirror-paired nuclei are more sensitive to the adopted strengths of the triplet-odd parameter $U$ rather than the triplet-even parameter $T$. Combining the quantitative constraint strengths of the triplet-even tensor part obtained from the magnetic dipole ($M1$) excitations, the charge-exchange Gamow-Teller states, and the spin-dipole excitations, the triplet-odd strengths are further constrained for the SLy5 as well as SGII effective interactions. This provides an alternative approach to constrain the appropriate magnitude of tensor force.

The dynamical influence of $\mathrm{\Lambda }$ hyperons on the excited-state properties of closed-shell multi-$\mathrm{\Lambda }$ Ca, Ni, Sn, and Pb hypernuclei is investigated using the self-consistent Hartree-Fock $+$ Random Phase Approximation in coordinate space. The strength distributions for the isoscalar monopole, isovector dipole, and isoscalar quadrupole modes are calculated, revealing a systematic upward energy shift with increasing $\mathrm{\Lambda }$ hyperon number $-S$. The scaling behavior of the computed centroid energies $\sqrt{m_1/m_{-1}}$ with respect to both the mass and hyperon number is determined. The nuclear incompressibility modulus $K_A$ is found to increase monotonically with $-S$. The largest value is found in the ${}_{50\mathrm{\Lambda }}{}^{258}\mathrm{Pb}$ hypernucleus, reaching $K_A=322$ MeV. Calculations in uniform hypernuclear matter confirm that this stiffening is a bulk effect driven by both the $N\mathrm{\Lambda }$ and $\mathrm{\Lambda }\mathrm{\Lambda }$ interactions. Analysis of the transition densities for states with maximal collective coherence indicates that the dynamical effect of $\mathrm{\Lambda }$ hyperons is predominantly in phase with the protons, especially in the case of the isovector $E1$ modes.

We perform an ab initio quantum Monte Carlo calculation of the isospin-symmetry-breaking correction ${\delta }_C$ to the superallowed $\beta$ decay of ${}^{10}\mathrm{C}$. Using both phenomenological and chiral nuclear interactions, we evaluate the Fermi matrix element and quantify its deviation from the canonical $\sqrt{2}$ value. The resulting ${\delta }_C$ values lie in the range $\approx 0.15–0.25\%$ and are consistent, within sizable uncertainties (approximately $34\%–65\%$ relative), across Hamiltonians, indicating no statistically significant dependence on the choice of nuclear interaction. The extracted values of $V_{\text{ud}}$ are also found to be compatible with current determinations within these uncertainties.

Low-resolution nuclear Hamiltonians, obtained from chiral effective field theory (EFT) and softened using renormalization group techniques, have been very successful in nuclear structure theory. The associated EFT truncation uncertainty for these potentials is difficult to quantify. We use singular value decompositions of low-resolution nuclear forces to obtain an operator basis to study Hamiltonian uncertainties for these potentials. We perform Bayesian inference for the singular values and three-body low-energy constants, the free parameters of nuclear Hamiltonians in our framework, using likelihoods based on nucleon-nucleon phase shifts and triton observables to account for the EFT truncation uncertainties in these quantities. Validating our inference, we find good reproduction of input uncertainties for low-energy phase shifts and three-nucleon observables. On the other hand, uncertainties for higher-energy phase shifts are systematically underestimated, which we attribute to limitations of the singular value decomposition and neglected correlations between phase shifts at different energies. We propagate the resulting distribution of Hamiltonians forward to predictions for ground-state properties of ${}^{24,28}\mathrm{O}$ and ${}^{48}\mathrm{Ca}$, comparing against other state-of-the-art nuclear structure predictions. Our approach makes it possible to account for EFT uncertainties when using low-resolution potentials, which is important for many ongoing studies in exotic nuclei.

In this study, we calculate the $\gamma Z$-exchange contribution to elastic $ep$ scattering at large momentum transfer within perturbative quantum chromodynamics (pQCD). We present analytical expressions for the $\gamma Z$-exchange contributions to the amplitudes. We also estimate the asymptotic behaviors of the amplitude contributions and of the physical quantity $A_{\text{PV}}$ at high momentum transfer. These asymptotic behaviors determine the subtraction order in the dispersion relations (DRs) satisfied by the amplitudes. At high $Q^2$ beyond the forward limit, our pQCD analysis shows that this subtraction order is fixed by the high-$\nu$ behavior of the amplitude coefficients $c_i^{\gamma Z,\text{PV}}$, and that $c_{3,A}^{\gamma Z,\text{PV}}$ requires a once-subtracted DR. Within the present pQCD framework and the adopted proton distribution amplitudes, these high-energy results also provide nontrivial constraints on low-energy DR assumptions.

Background: Due to its large production cross section, ${}^{254}\mathrm{No}$ is the most-studied nucleus in the transfermium region and has been the “pioneer” nucleus in many different types of studies ranging from in-beam and decay $\gamma$-ray spectroscopy to $\gamma$-ray calorimetry. ${}^{254}\mathrm{No}$ is a well-deformed nucleus. At low excitation energy, the spins (I), parities ($\pi$), and excitation energies of three rotational bandheads are known: the $0^{+}$ ground state; a two-quasiproton $I^{\pi }=3^{+}$ state at an excitation energy of 987 keV, which decays promptly to the ground-state rotational band; and a long-lived $8^{-}$ state at 1297 keV, whose microscopic configuration is still under debate.

Purpose: This paper reexamines the electromagnetic decay of the long-lived $8^{-}$ state in ${}^{254}\mathrm{No}$ using the enhanced sensitivity to the detection of internal conversion electrons of the GABRIELA detector array installed at the focal plane of the recoil separator SHELS at the Joint Institute for Nuclear Research in Dubna.

Methods: ${}^{254}\mathrm{No}$ nuclei were produced in fusion-evaporation reactions between ${}^{48}\mathrm{Ca}$ ions and the atoms of ${}^{208}\mathrm{Pb}$ targets. The evaporation residues of interest were separated from the background of other reaction products by the recoil separator SHELS and transported to the GABRIELA decay station where the $\gamma$ as well the internal-conversion decay from the $8^{-}$ isomer could be jointly observed for the first time. Standard spectroscopy techniques together with a Geant4-assisted analysis of the spectroscopic data were used to establish the decay scheme of the $8^{-}$ isomer.

Results: The observed $\gamma$ ray and internal-conversion-electron singles and coincidence spectra have revealed new decay branches from the $8^{-}$ isomer as well as new states lying below it. A $4^{+}$ state has been established at 1203 keV above the ground sate. The presence of a $2^{-}$ octupole phonon state could also be suggested at 1114 keV. The spectrum of detected internal-conversion electrons has uncovered the existence of an intense electric monopole ($E0$) contribution stemming from the decays of one or more states lying below the $3^{+}$ state. These findings are discussed in the light of quasiparticle random-phase approximation (QRPA) based on the finite-range D1M Gogny force and a new extension of the discrete nonorthogonal shell model including a variation-after-projection approach.

Conclusions: The newly identified $4^{+}$ state is interpreted as the unfavored angular momentum coupling of two protons occupying the same single-particle configurations as the protons forming the previously known $3^{+}$ state. The two states form what is called a Gallagher-Moskowski doublet. This interpretation is supported by both the QRPA and shell-model calculations. The energy difference between the $3^{+}$ and $4^{+}$ states provides the first experimental measurement of spin splitting between two quasiproton states in the actinide region. The excess $E0$ strength evidenced by the internal-conversion-electron spectrum is attributed to the decay of members of a second $0_2^{+}$ rotational band lying at 884 keV above the ground state, which is weakly populated in the decay of the $3^{+}$ band. Remarkably, a $0_2^{+}$ state is obtained at 859 keV above the ground state in the new shell-model description of ${}^{254}\mathrm{No}$, which also reproduces the sequence and electromagnetic-decay properties of the ground-state and $3^{+}$ rotational bands.