We evaluate pairwise correlations using ground-state wave functions for ${}^4\mathrm{He}$ and ${}^6\mathrm{He}$ obtained by ab initio no-core shell model calculations with the Daejeon16 nucleon-nucleon interaction plus Coulomb interaction, to characterize the structures of these two systems. We demonstrate that two-nucleon spatial correlations, specifically the pair-number operator $r^0$ and the square-separation operator $r^2$ projected on two-body spin $S$ and isospin $z$ components encode important details of the halo structure of ${}^6\mathrm{He}$. We also analyze the single-particle state occupancies and the two-body state occupancies for the ground state of ${}^4\mathrm{He}$ and ${}^6\mathrm{He}$. Our results indicate that the two valence neutrons in the ground state of ${}^6\mathrm{He}$ dominantly form a spin-singlet configuration. The rms pair separations between core nucleons and halo neutrons of ${}^6\mathrm{He}$ are, on average, about 80% larger than pair separations within the swollen and off-centered “$\alpha$ core.” We show that this off-centering effect is primarily responsible for the observed increase in point-proton radius $r_p$ in ${}^6\mathrm{He}$ relative to ${}^4\mathrm{He}$.

The measurement of fragmentation cross sections for nuclei up to ${}^{56}\mathrm{Fe}$ on light elements found in the human body (e.g., H, C, and O) is of fundamental importance for particle therapy (PT) and radioprotection in space (RPS), as well as for advancing cosmic-ray physics. These measurements can significantly improve the accuracy of dose calculations for patients during PT treatments and for astronauts exposed to cosmic radiation during deep-space missions. Among the many ions of interest, ${}^{16}\mathrm{O}$ is used in PT and is the most abundant species within the HZE component of cosmic rays. This paper presents the results of angular nuclear fragmentation cross sections for the production of He, Li, Be, B, C, and N nuclei in the interaction of a $400\mathrm{MeV}/\mathrm{nucleon}$ ${}^{16}\mathrm{O}$ beam with a hydrogen and polyethylene target. The fragmentation on the hydrogen was measured by combining the results on polyethylene with recent measurements on a graphite target. While the fragmentation on hydrogen is fundamental for improving nuclear interaction models, allowing more accurate predictions of dose distributions in PT and RPS, polyethylene has proven to be a promising shielding material in radiation protection models. The data analyzed were collected in 2021 at the GSI Helmholtz Center for Heavy Ion Research facility in Darmstadt (Germany) by the FOOT Collaboration. All results were compared with different Monte Carlo models for light ion fragmentation physics in the energy range of interest implemented in FLUKA and Geant4.

To investigate the mechanism of $\alpha$-particle production, energy-angle correlations of the emitted $\alpha$ particles have been measured for the ${}^6\mathrm{Li}+{}^{93}\mathrm{Nb}$ system at energies around the Coulomb barrier. Results of three-body Monte Carlo simulations for breakup are in good agreement with the measured experimental energy-angle correlations. This is in contrast to the observation involving ${}^7\mathrm{Li}$ projectile, where breakup simulation failed to reproduce the experimental data. Comparison of the data with two different semiclassical prescriptions for the optimum $Q$ value leads to conflicting results, so no firm conclusion could be extracted from this comparison. Instead, fully quantum-mechanical calculations, employing the continuum-discretized coupled-channels (CDCC) method for the elastic breakup component and the Ichimura-Austern-Vincent (IAV) for the nonelastic one, reproduce the present experimental data rather well. The present study highlights the complexity of weakly bound projectile interactions and emphasizes the importance of more such studies for a comprehensive understanding.

For the spectroscopy of nucleon resonances at the total energies from the ${\eta }^{\prime }$-meson production threshold to 2.32 $\mathrm{GeV}$, photon beam asymmetries of the reaction $\gamma p\to {\eta }^{\prime }p$ were measured together with total and differential cross sections by analyzing the two decay modes ${\eta }^{\prime }\to \gamma \gamma$ and ${\pi }^0{\pi }^0\eta$. New constraints for amplitude decomposition were given by the first-time result of photon beam asymmetries at $E_{\gamma }>1.84 \mathrm{GeV}$ and the most precise data of differential cross sections to date at extremely backward ${\eta }^{\prime }$ angles. The possibility of a larger coupling constant of the ${\eta }^{\prime }$-nucleon system to the $N\left(2250\right)$ resonance was implied in the partial wave analyses using the present data.

Within the shell-model framework, we have derived a new effective interaction from the realistic N3LO interaction to provide an accurate description of the nuclear structure properties of even-even nuclei with $50\le Z, N\le 82$, in the ${}^{132}\mathrm{Sn}$ mass region. We validate our theoretical framework and the reliability of the new effective interaction by comparing the calculated energy levels, $E2$ transition rates, and magnetic dipole moments with experimental data. Special attention is devoted to the evolution of collectivity; an in-depth study of the quadrupole properties of different nuclei in this region reveals the presence of triaxial $\gamma$ bands.

The Woods-Saxon (WS) potential, a well-established model describing the central mean field potential in atomic nuclei, plays a critical role in studies of nuclear structure and nuclear reactions. Currently, research on the WS potential primarily focuses on the forward problem, solving for wave functions given the potential, whereas the inverse problem of inferring WS potential parameters from wave functions remains underexplored. In this work, three WS central potential parameters, the depth $V_0$, radius $R_0$, and diffuseness $a_0$ are selected. Corresponding wave functions are calculated using the WS potential model, and a Gaussian process emulator is trained, achieving a coefficient of determination $R^2=0.99$, and the mean absolute error is 0.0015 on the test set. The wave functions associated with $V_0=-50$ MeV, $R_0=3.5$ fm, $a_0=0.45$ fm are treated as experimental evidence. Using Bayesian analysis, we obtain posterior distributions for the parameters, $V_0=-50.{30}_{-5.27}^{+5.00}$ MeV, $R_0=3.{56}_{-0.06}^{+0.07}$ fm, $a_0=0.{43}_{-0.04}^{+0.04}$ fm. The central values of the posterior distributions agree closely with the true values, and the full distributions encompass the target WS potential parameters. This demonstrates that Bayesian inference can successfully invert WS parameters from theoretical wave functions, thereby offering a robust new approach for potential inversion and for exploring complex nuclear systems such as exotic nuclei and high-energy scattering processes.

The neutron radiative capture reaction ${}^{17}\mathrm{O}(n,\gamma ){}^{18}\mathrm{O}$ plays a pivotal role in both nuclear structure studies and astrophysical nucleosynthesis, particularly in the formation of elements during hydrostatic and explosive stellar environments. We calculated the ${}^{17}\mathrm{O}(n,\gamma ){}^{18}\mathrm{O}$ cross section within the Skyrme Hartree-Fock potential model and analyzed electric dipole $E1$ transitions to both positive- and negative-parity states below the α-decay threshold in ${}^{18}\mathrm{O}$. Our cross sections are significantly different from the data available in commonly used libraries. We further investigate the impact of the new calculated cross section on weak $r$-process nucleosynthesis using large-scale reaction network calculations across a wide range of electron fractions and entropies. Our results show that the ${}^{17}\mathrm{O}(n,\gamma ){}^{18}\mathrm{O}$ reaction rate significantly influences the production of first $r$-process peak elements, such as strontium, under specific astrophysical conditions. This study highlights the importance of accurate nuclear data for light isotopes in modeling heavy-element synthesis and provides updated reaction rates for future nucleosynthesis simulations.

A multinucleon transfer reaction with a ${}^{136}\mathrm{Xe}$ beam and a gold-backed ${}^{176}\mathrm{Yb}$ target populated isomers in $N=108{}^{178}\mathrm{Yb}$ and ${}^{179}\mathrm{Lu}$. The single decay from the $t_{1/2}=203$(16) ns isomer in ${}^{178}\mathrm{Yb}$ to the $I^{\pi }=4^{+}$ level in the ground-state band suggests a $I^{\pi }=4^{-}$ assignment, and multiquasiparticle calculations associate this state with the $K^{\pi }=4^{-}, {\nu }^2(1/2\left[510\right],9/2\left[624\right])$ configuration. At least two isomers were observed in ${}^{179}\mathrm{Lu}$. One likely couples the $K^{\pi }=4^{-}$ configuration found in ${}^{178}\mathrm{Yb}$ to the $9/2\left[514\right]$ quasiproton orbital to form a $K^{\pi }=17/2^{+}$ level ($t_{1/2}=1.0\left(4\right)\mu \mathrm{s}$) which primarily decays into the rotational band based on the 9/2[514] state. A second isomer was observed to decay into this same band, but at higher energy and spin. Based on its feeding pattern, its similarity to an isomer found in ${}^{181}\mathrm{Ta}$, and a multiquasiparticle calculation, it is proposed to correspond to a $K^{\pi }=29/2^{-}$ state based on the $\pi 9/2\left[514\right]{\nu }^2(9/2\left[624\right],11/2\left[615\right])$ configuration. An analysis of the reduced hindrance factors for negative-parity, two-quasineutron isomers in the rare-earth region is presented as well.

Nuclear lattice effective field theory (NLEFT) is an efficient ab initio tool for solving nuclear many-body systems using the imaginary-time projection technique, where the preparation of trial states is essential for substantially reducing the computational cost required to achieve the desired numerical precision. It has been challenging in forming optimal multireference trial states using multiple Slater determinants within auxiliary-field-based quantum Monte Carlo frameworks like NLEFT. In this work, we develop a novel sampling method for efficiently incorporating such multireference trial states into NLEFT calculations. We applied the optimized trial state to ${}^7\mathrm{Li}$ and ${}^8\mathrm{Li}$, finding overall improvements in calculated energies, electromagnetic properties, and transitions compared to results obtained without these optimizations. Our approach provides a reliable foundation for accurately simulating nuclear ground and low-lying excited states within the NLEFT framework.

Background: The complex scaling method (CSM) has been successfully used to describe many-body resonances as eigenvalues of the complex-scaled Hamiltonian in an appropriate $L^2$ basis representation. Its scope has subsequently been extended to many-body continuum states, strength functions, and scattering observables. However, a general framework that incorporates time evolution within the same CSM framework has not yet been established.

Purpose: We formulate a time-evolution formalism as a natural extension of the CSM based on the extended completeness relation (ECR), and apply it to the electric dipole ($E1$) excitation of ${}^6\mathrm{He}$ in order to clarify how an initially correlated three-body configuration evolves into continuum states.

Methods: Time evolution is described by a complex-scaled time-evolution operator represented with the ECR. The formalism is first tested in a simple two-body model through comparison with a direct numerical solution of the time-dependent Schrödinger equation. It is then applied to the $E1$ excitation of ${}^6\mathrm{He}$ in an $\alpha +n+n$ three-body model, and the density distributions are analyzed in different Jacobi coordinate systems.

Results: The present formalism reproduces the wave-packet evolution obtained in the direct time-dependent calculation. In the application to ${}^6\mathrm{He}$, the initial $E1$-excited state exhibits a correlated configuration and evolves into spatially extended continuum states. The time evolution of the density distributions indicates the coexistence of sequential decay through a core-neutron subsystem and direct breakup.

Conclusions: The present formalism extends the scope of the CSM from spectral and scattering observables to real-time continuum dynamics, and provides a unified framework that connects initial-state correlations, continuum structure, and decay dynamics in weakly bound nuclei.

Physics-informed neural networks (PINNs) have emerged as a powerful tool for solving differential equations, yet their application to nuclear scattering has been hindered by the oscillatory, nondecaying nature of scattering wave functions. In this work, I demonstrate that exterior complex scaling (ECS) transforms scattering boundary conditions into exponentially decaying waves suitable for neural network solutions, enabling PINNs to solve nuclear reaction problems for the first time. I develop a driven-equation formulation where the source term is confined to the real axis, avoiding the need to analytically continue nuclear potentials into the complex plane. The method is validated on nucleon-nucleus scattering ($\mathrm{n}+{}^{40}\mathrm{Ca}$ at $E_{\text{lab}}=20\mathrm{MeV}$) with 21 partial waves, achieving phase shift accuracy of $\mathrm{\Delta }\delta \lesssim 0.1^{\circ }$ for the strongly absorbed channels ($\ell \le 4$) and $\mathrm{\Delta }\delta \le 0.{60}^{\circ }$ for all channels up to $\ell =10$, when compared with conventional solvers. I further demonstrate the approach on heavy-ion scattering (${}^6\mathrm{Li}+{}^{208}\mathrm{Pb}$ at 40 MeV) with 41 partial waves and strong Coulomb effects, where an auto-adaptive anchor warm-down for weak-source channels yields a mean $S$-matrix accuracy of $\left|\mathrm{\Delta }\right|S_{\ell }\left|\right|\approx 3\times {10}^{-3}$ across the full angular momentum range, including the absorption-to-transparency transition region. This work establishes the foundation for extending PINNs to inverse problems where end-to-end differentiability enables direct fitting of optical potential parameters, coupled-channel reactions, and few-body scattering, where traditional grid methods face exponential scaling.

Central ${}^{136,124}\mathrm{Xe}+{}^{124,112}\mathrm{Sn}$ collisions from INDRA data are analyzed using a Bayesian inference on light nuclei multiplicities to estimate the thermodynamical parameters and in-medium modification of the cluster self-energies within a relativistic mean-field model. An excellent description of experimentally measured abundances of H and He isotopes is obtained. We examine two possible modeling of in-medium effects as an increased in-medium effective mass or an increased vector repulsion. We show that these physical pictures cannot be discriminated by the data. In both cases, the temperature dependence of the meson couplings leads to a faster weakening of the light cluster abundances with temperature than previous studies predicted. Possible systematic errors due to out-of-equilibrium effects affecting the experimental abundances are considered by repeating the Bayesian inference with reduced information. The abundance prediction of the species excluded from the constraint is well compatible with the experimental data, suggesting that there is no a priori need of accounting for nonequilibrium effects or finite state interactions that potentially affect the deuteron yield.

Measurement of particle emission source is a fundamental objective of femtoscopy in high-energy nuclear collisions. Conventional analyses rely on Gaussian parametrizations of pair emission sources, which makes the extraction of single-particle emission sources challenging, particularly for rare particles. Here, we introduce a novel statistical reconstruction method that allows extracting information of the target source relative to a data-constrained reference source instead of the Gaussian assumption. The correlation function is expressed as an ensemble average over the single-particle-conditioned correlation kernel, defined as the particle-by-particle contribution to the correlation function conditioned by the target particles. For particles with rare yields, the particle-by-particle distribution of this kernel can be transformed into event-by-event extraction and becomes experimentally accessible, enabling a direct statistical reconstruction of the emission source of single particles, instead of inferring a pair source. We apply this method to reconstruct $J/\psi$ source via $p\text{−}J/\psi$ correlations, using HAL QCD-derived $NJ/\psi$ potentials in $\sqrt{s}=13.6$ TeV $pp$ collisions simulated with EPOS4HQ. The reconstructed source reproduces the key characteristics and this new approach achieves a systematic uncertainty of approximately $13\%$ based on EPOS4 simulation.

Two pairs of doublet bands with opposite parities have been identified in ${}^{118}\mathrm{I}$ via in-beam $\gamma$-ray spectroscopy techniques. The present experimental energy levels and reduced transition probabilities indicate that they are two distinct chiral doublet bands with the $\pi g_{9/2}^{-1}\otimes \nu h_{11/2}$ and $\pi h_{11/2}^1\otimes \nu h_{11/2}$ configurations, respectively. This interpretation is further supported by the constrained triaxial covariant density functional theory and triaxial particle rotor model calculations. The present work reports the observation of multiple chiral doublet bands based on different configurations involving only intruder orbitals.

The short-distance production of multiparticle states in high-energy nuclear reactions provides a unique way to study the low-energy properties of few-body systems. In particular, the production amplitude of multineutron systems is strongly constrained by an approximate conformal symmetry of the underlying theory. We calculate the full amplitude for the short-distance production of three particles with large scattering length in leading-order pionless EFT, focusing on the cases of three neutrons and three spinless bosons. We investigate the signature of low-energy resonances and other correlations in the relative energy distributions. For the case of neutrons, we compare to the predictions from approximate conformal symmetry close to the unitary limit and calculate the range corrections up to next-to-next-to-leading order.

Background: Experimental data on $\alpha$-particle inelastic scattering for monopole excitations in ${}^{24}\mathrm{Mg}$ in the excitation-energy region $E_{\mathrm{x}}=9–25$ MeV, obtained at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS), have been analyzed within a fully self-consistent quasiparticle random-phase approximation (QRPA) framework using two Skyrme parametrizations. A good overall agreement with the experimental data is achieved, particularly with the ${\mathrm{SkP}}^{\delta }$ force, which corresponds to a low nuclear incompressibility of $K_{\infty }=202$ MeV.

Purpose: To extract energy scales, by means of wavelet analysis, characterizing the observed fine structure in the main peak of the isoscalar giant monopole resonance (ISGMR) as well as the low-energy region 10–18 MeV of the deformation-induced monopole-quadrupole coupling (MQC) in order to investigate the damping mechanism contributing to their decay widths.

Methods: Characteristic energy scales and power spectra are extracted from the fine structure using continuous wavelet transforms. The experimental results are compared to QRPA calculations employing the Skyrme parametrizations ${\mathrm{SkP}}^{\delta }$ and SVbas.

Results: A significant, if not decisive, impact of the MQC strength on the wavelet power spectra is observed across the entire excitation-energy range of 10–24 MeV. Wavelet features derived from the QRPA and from unperturbed two-quasiparticle monopole strengths are compared. The results demonstrate that the residual interaction plays a key role in reproducing wavelet powers and characteristic energy scales. Overall, a continuous range of scales $\delta E=200–1000$ keV is obtained rather than distinct isolated scales. The deformation softness of ${}^{24}\mathrm{Mg}$ is found to significantly influence both the monopole strength distribution and the wavelet characteristics.

Conclusions: Similar to the case of the isovector giant dipole resonance, the dominant role of Landau damping is confirmed as the main decay mechanism of the ISGMR in the highly deformed nucleus ${}^{24}\mathrm{Mg}$. At the same time, the remaining discrepancies between experiment and theory highlight the possible importance of couplings to more complex configurations.

We investigate the thermodynamical stability of low-density isospin-symmetric nuclear matter at finite temperature, explicitly including light clusters as degrees of freedom. Within a generalized mean-field framework, we compute the curvature matrix of the free-energy density and determine the spinodal region, identifying the conditions under which mechanically unstable modes may develop in the presence of clustering. Particular attention is devoted to the formal consequences of introducing an infrared momentum cutoff in the density and current moments, which effectively accounts for Pauli-blocking effects and the associated reduction of low-momentum quasiparticle states in the medium. We show that when the cutoff is density dependent, thermodynamic consistency requires additional contributions to the chemical potentials, and extra terms also appear in the first hydrodynamic moment, influencing both the stability analysis and the location of the spinodal boundary. We further examine the character of the unstable modes and find that a sufficiently stiff density dependence of the cutoff may drive clusters to fluctuate out of phase with nucleons, pushing them toward low-density regions while nucleonic instabilities grow, in contrast with the in-phase pattern obtained when the density derivatives of the cutoff are neglected in the stability analysis. Our results shed new light on the role of light clusters in the phase dynamics of warm, dilute nuclear matter, with implications for heavy-ion collisions and for the physics of neutron-star crusts.

The low-lying excited states of ${}^{46}\mathrm{S}$ and ${}^{47}\mathrm{S}$ were investigated using knockout reactions on a liquid hydrogen target combined with $\gamma$-ray spectroscopy. Four new transitions were observed in ${}^{46}\mathrm{S}$, and a single $\gamma$ ray was identified in ${}^{47}\mathrm{S}$. Comparison with shell-model calculations allowed the assignment of the observed transitions to specific theoretical levels. The energies of the $4_1^{+}$ and $2_2^{+}$ states in ${}^{46}\mathrm{S}$ suggest the presence of triaxial deformation.