A high-precision experiment in search of the predicted Efimov state in ${}^{12}\mathrm{C}$ at 7.458 MeV excitation energy was performed. Using a state-of-the-art detector system and novel analysis techniques, it was possible to isolate potential Efimov state events at the predicted energy level above the $3\alpha$ threshold with much better sensitivity in the ${}^{12}\mathrm{C}$ excitation energy spectrum compared to the existing data. The mutual ${}^8\mathrm{Be}$ resonance (91.84 keV) condition filters out a total of 21 probable Efimov state events around 7.458 MeV. With $2\sigma$ confidence, it gives an upper limit of $0.014\%$ for the Efimov state $\alpha$-decay branching ratio, which is about an order of magnitude smaller than the latest upper limit found in the literature. This observation was supported by a new penetrability calculation assuming a relatively extended structure for the Efimov state compared to the Hoyle state. However, the triple-$\alpha$ reaction rate, including both the Hoyle state and the Efimov state, was found to be much larger than the allowed limit, strongly suggesting that the Efimov-like state may not exist in ${}^{12}\mathrm{C}$.

This study constrains the range of in-medium mass modification through a comparison of theoretical calculations with experimental transverse momentum spectra and the yield ratio $\overline{p}/p$ of protons and antiprotons. Based on the constrained range and a Gaussian source model with radial flow, the theoretical predictions for the fermion back-to-back correlation (fBBC) of $p\overline{p}$ pairs at BNL Relativistic Heavy Ion Collider energies are presented. The results reveal a strong sensitivity of the fBBC signal to the assumed source time distribution: a Lorentzian form generates a pronounced high-momentum signal, whereas an $\alpha$-stable Lévy form leads to a marked low-momentum signal. Moreover, the in-medium mass modification is shown to enhance the yield ratio $\overline{p}/p$. Therefore, events characterized by a larger $\overline{p}/p$ ratio are predicted to have a significantly higher probability of exhibiting a detectable fBBC signal. This study may propose a promising new direction for the experimental observation of this phenomenon.

We compute radiative corrections to the superallowed $\beta$ decay of ${}^{10}\mathrm{C}$ in an effective field theory approach using nuclear matrix elements obtained from quantum Monte Carlo calculations. These corrections are an important ingredient in the extraction of the Cabibbo-Kobayashi-Masakawa quark mixing matrix element $V_{ud}$, and the role of this work is to illuminate the uncertainties arising from nuclear structure. Our results provide good agreement with both the traditional extraction of $V_{ud}$, as well as with a more recent evaluation performed using the no-core shell model and a dispersion formalism. The dominant uncertainty in this approach is the presence of two unknown low-energy constants that enter into the relevant nuclear matrix elements. Future determinations of these low-energy constants—either from QCD or modeling them with two nucleon amplitudes—would improve the precision of the extraction in this formalism.

In the present work, we focus on reactions around ${}^{85}\mathrm{Rb}$, relevant to the astrophysical $\gamma$ process, where reaction flow is defined by the competition between two channels, the $(\gamma ,n)$ and the $(\gamma ,p)$. The $(\gamma ,p)$ channel was constrained in a previous measurement of the ${}^{84}\mathrm{Kr}(p,\gamma ){}^{85}\mathrm{Rb}$ reaction at Michigan State University using the Summing NaI(Tl)(SuN) detector. Here we present a reanalysis of the same data in which we provide new values for the reaction cross section, and in addition, we use the $\gamma$-ray spectra to constrain the statistical properties of ${}^{85}\mathrm{Rb}$, namely the nuclear level density (NLD) and the $\gamma$-ray strength function ($\gamma \mathrm{SF}$). Using these experimental inputs, we were able to provide a more stringent constraint on the ${}^{85}\mathrm{Rb}(\gamma ,n){}^{84}\mathrm{Rb}$ reaction channel. In addition, the proton optical model potential (pOMP) parameters were modified to obtain a better fit on the experimental data of $(p,\gamma ), (p,n)$, and $(p,2n)$ reaction channels. The constrained NLD and $\gamma \mathrm{SF}$, as well as the modified pOMP, were used to calculate the astrophysical reaction rates for the ${}^{85}\mathrm{Rb}(\gamma ,p){}^{84}\mathrm{Kr}$ and ${}^{85}\mathrm{Rb}(\gamma ,n){}^{84}\mathrm{Rb}$ channels. Based on our results, we conclude that the $(\gamma ,n)$ channel dominates at temperatures relevant for the production of the light $p$ nuclei.

Improvement of the accuracy of neutronics simulation of actual or future reactor designs is essential and requires a better knowledge of the core neutron population. The reactor neutron population is partially driven by $(n,xn)$ reactions that change the number and decrease the energy of the neutrons. However, the cross sections of these reactions are currently not measured with sufficient precision. This is particularly the case for the neutron inelastic-scattering cross section of ${}^{238}\mathrm{U}$, which represents around 90%–95% of the mass of fuel in present and many future reactor core designs. It therefore features on the High Priority Request List for measurement improvement. This cross section can be measured using prompt $\gamma$-ray spectroscopy coupled to neutron time-of-flight measurements, where the total $(n,n^{\prime })$ cross section can be deduced from a combination of the measured $(n,n^{\prime }\gamma )$ partial cross sections and the level scheme information. The knowledge of the ${}^{238}\mathrm{U}$ level scheme is still very incomplete, inducing significant uncertainties on the resulting inelastic-scattering cross section. Therefore, an effort has recently been carried out to experimentally revisit the ${}^{238}\mathrm{U}$ decay scheme by performing high-resolution coincidence spectroscopy of the ${}^{238}\mathrm{U}(n,n^{\prime })$ reaction. To obtain detailed level scheme information, the $\nu$-Ball $\gamma$ spectrometer was coupled to the LICORNE directional neutron source of the ALTO facility, allowing the study of inelastic scattering of fast neutrons (0.5–3 MeV) on ${}^{238}\mathrm{U}$ via $\gamma \text{−}\gamma$ coincidence spectroscopy. Coincidence matrices obtained during the first and the second $\nu$-Ball campaigns were analyzed using the RadWare ESCL8R software. 110 $\gamma$ transitions and 60 levels registered in the Evaluated Nuclear Structure Data File database have been confirmed, and 158 new $\gamma$ transitions and 58 new levels have been found. Although not exhaustive, the ${}^{238}\mathrm{U}$ level scheme information has been significantly improved, and its completeness has been estimated to be up to 1.7214 MeV compared with 1.27854 MeV at present. It is hence expected to decrease the uncertainties of ${}^{238}\mathrm{U} (n,n^{\prime })$ cross sections, which is needed for accurate reactor core modeling.

High-spin structures of holmium ($Z=67$) and erbium ($Z=68$) isotopes are presented near mass 160, a region where collective and single-particle modes of excitation compete in the generation of angular momentum at the highest experimentally attainable spins in atomic nuclei. The level schemes of the ${}^{156,157,158}\mathrm{Ho}$ isotopes have been significantly extended, reaching spins in the $40\hslash$ to $55\hslash$ range, through multiple experiments utilizing the Gammasphere spectrometer. In particular, several new noncollective band-terminating states are reported for these nuclei. The nature of these states, including both valence-space terminations and core-excited oblateconfigurations, is discussed in terms of proton particle-hole (p-h) excitations across the semimagic $Z=64$ shell closure. Cranked-Nilsson–Strutinsky (CNS) calculations have been used to interpret the nature of these noncollective states. The corresponding terminating states in ${}^{154–159}\mathrm{Er}$ are also included, providing a systematic description of band termination in this mass region. In addition, three weak rotational structures have been assigned to ${}^{157}\mathrm{Ho}$ at the highest spins. These collective bands are proposed to be based on a triaxial strongly deformed nuclear shape, involving neutron p-h excitations across the $N=82$ shell gap.

Conventionally, octupole deformation in nuclei has been attributed to strong $\mathrm{\Delta }l=3$ couplings between opposite-parity single-particle orbitals. In this work, we demonstrate that the often-overlooked $\mathrm{\Delta }l=1$ mode also plays an important role. Taking orbitals near the octupole magic number $N=134$ as a benchmark, we systematically evaluate the $\mathrm{\Delta }l=1$ and $\mathrm{\Delta }l=3$ mixing ratios of the wave functions within the Nilsson model. We introduce component-resolved single-particle octupole energy contributions, based on the Hellmann-Feynman relation, to quantify the contributions of each $(\mathrm{\Delta }l,\mathrm{\Delta }j)$ coupling. Furthermore, the impact of $\mathrm{\Delta }l=1$ coupling on the rotational structure is demonstrated via particle-rotor model calculations for ${}^{221}\mathrm{Ra}$ and ${}^{223}\mathrm{Th}$. Our work suggests that $\mathrm{\Delta }l=1$ and $\mathrm{\Delta }l=3$ octupole couplings act synergistically in driving reflection asymmetry, necessitating a revised paradigm for understanding octupole correlation.

The isospin properties and the collectivity of the pygmy dipole resonance (PDR) are longstanding open questions in nuclear structure studies. To answer these questions, the $\gamma$ decay of PDR states in ${}^{208}\mathrm{Pb}$ to the low-lying $2_1^{+}$ state is investigated using the Skyrme particle-vibration coupling model. It is found that the $E1 \gamma$ decay from the PDR states to the low-lying $2_1^{+}$ state is strongly suppressed compared to that from the isovector giant dipole resonance (IVGDR), which reveals the predominantly isoscalar character of PDR. A detailed decomposition of the decay diagrams of the amplitudes of the processes contributing to the decay demonstrates the non-negligible presence of the one-particl–one-hole configurations coupled to the $2_1^{+}$ phonon in the PDR wave function. Furthermore, we give a quantitative way to identify the components of complex-configurations in the wave function, and it is found that such component in PDR is smaller than that in IVGDR and much smaller than that in isoscalar giant quadrupole resonance (ISGQR). However, by analyzing the $E2 \gamma$ decay of the PDR and IVGDR to the $3_1^{-}$ state, we find that the $3_1^{-}$ phonon component is larger in the PDR wave function than in the IVGDR.

The solution of large-scale eigenvalue problems is crucial in nuclear many-body theory, where Hamiltonian matrices often reach extremely large dimensions. Quantum computing opens new perspectives for addressing such demanding problems. Although the quantum phase estimation algorithm offers, in principle, a systematic route to matrix diagonalization, its practical deployment demands levels of coherence and error correction that current quantum hardware cannot yet support. A viable near-term strategy is instead to exploit quantum annealing, which enables the recasting of eigenvalue problems into quadratic unconstrained binary optimization formulations that can be addressed by existing annealing-based processors. Here, we propose a hybrid quantum-classical algorithm that combines quantum annealing and classical deflation to iteratively extract the full eigenspectrum of both standard and generalized eigenvalue problems. We benchmark this method on eigenvalue problems arising from the equation-of-motion phonon method performing calculations on real quantum hardware. Our approach illustrates the capabilities and limitations of near-term quantum devices in addressing nuclear eigenvalue problems.

We present a physics-embedded Bayesian neural-network (PE-BNN) framework that integrates fission product yields (FPYs) with prior nuclear physics knowledge to predict energy-dependent FPY data with fine structure. By incorporating a phenomenological shell-related input feature with an excitation-energy damping term, the PE-BNN captures both fine structures and global energy trends. The combination of this physics-informed input with hyperparameter optimization via the Watanabe-Akaike Information Criterion (WAIC) significantly enhances predictive performance. Our results show that the PE-BNN framework is well suited to observables whose systematic features can be encoded as model inputs, and that it remains consistent with known shell-related trends and independently measured prompt-neutron systematics.

Nucleon momentum distributions (NMDs) reveal essential information about Fermi motion and short-range correlations (SRCs). In extracting NMDs from inclusive electron scattering data, theoretical analyses, such as the scaling analysis, are typically employed. For complex nuclei, consistently treating the excitation energy of the residual system is a complicated task, leading to discrepancies between existing extracted NMDs and ab initio calculations, particularly around the Fermi momentum $k_F$. To address this issue, we introduce an improved description of the excitation energy in the framework of the relativistic Fermi gas model. With this treatment, the extracted NMDs of complex nuclei show better agreement with ab initio calculations across the low- and high-momentum range, especially around $k_F$, successfully reproducing both the behaviors of Fermi motion and SRCs. These results provide a new experimental perspective on the interplay between Fermi motion and SRCs in complex nuclei.

Values of the quenching factor $Q$ and respectively specified Landau-Migdal parameter $g^{\prime }$ are deduced from a detailed comparison of experimental and theoretical Gamow-Teller strength distributions in the ${}^{48}\mathrm{Ca}, {}^{90}\mathrm{Zr}, {}^{132}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ parent nuclei. The theoretical distributions are obtained within the simply modified basic version of semimicroscopic particle-hole dispersive optical model, which has been successfully used for describing high-energy particle-hole-type charge-exchange spin-monopole excitations in mentioned parent nuclei. The deduced values are compared with those obtained in other studies. Values of adjusted “spreading” parameters of the model are also deduced from the above-mentioned comparison.

The earliest phase of an ultrarelativistic heavy ion collision can be described as a highly populated system of gluons called glasma. We study some glasma characteristics related to the system's angular momentum. The first one is the global angular momentum perpendicular to the reaction plane, which is spanned by the beam axis and impact parameter vector. We show that only a small fraction of the enormous initial angular momentum of the colliding ultrarelativistic nuclei is transferred to the glasma. Our main focus is the glasma angular momentum directed along the beam axis. This quantity has a local character and results from the inhomogeneous velocity field generated in the glasma. We calculate the vorticity and local angular momentum which show noticeably different behavior. The results are analyzed in detail and discussed in the context of existing experimental data. We argue that neither vorticity nor thermal vorticity but instead the local angular momentum controls the polarization of final-state hadrons.

We present a data-driven deep learning framework for predicting multiple bulk observables in $\mathrm{Au}+\mathrm{Au}$ collisions at energies available at the BNL Relativistic Heavy Ion Collider (RHIC). A single neural network is trained exclusively on experimental measurements of charged-particle pseudorapidity density distributions, transverse momentum spectra, and elliptic flow coefficients over a broad range of collision energies and centralities, without using simulation outputs as training targets. The network architecture is inspired by the stages of a heavy-ion collision, from the quark-gluon plasma to chemical and kinetic freeze-out, and employs locally connected hidden layers and a structured input design that encodes basic geometric and kinematic features of the system. We demonstrate that these physics-motivated choices significantly improve test performance compared to purely fully connected baselines. The trained model is then used to predict the above observables at energies available at the RHIC, and the results are further cross-checked against the energy dependence of the total charged-particle multiplicity per participant pair, as well as against a CLVisc hydrodynamic calculation with ${\mathrm{T}}_{\mathrm{R}}{\mathrm{ENT}}_{\mathrm{o}}$ initial conditions. Our findings indicate that such physics-guided neural networks can provide useful data-driven interpolation tools for RHIC observables in regions not currently covered by the available measurements and can support further phenomenological studies.

In this article, the surface tension and stability of quark matter modified by the vector interaction in a strong magnetic field are investigated in the quasiparticle model with the multiple reflection expansion. The self-consistent thermodynamic treatment of the chemical-potential-dependent quark mass is maintained by the effective bag function, which depends on both the chemical potential and the magnetic field. It is found that the vector interaction could enlarge the surface tension in both the parallel and transverse directions with respect to the magnetic field. In a stronger magnetic field region, the presence of the vector repulsive interaction leads to an increase in transverse surface tension with the magnetic field strength, which is opposite to the vanishing value without repulsive interaction in the previous work. Consequently, it is concluded that a moderate-intensity magnetic field is required for the formation of a quark-matter bubble with the vector interaction. Finally, it is demonstrated that the vector interaction slightly reduces the stability of quark matter.

Using $(10087\pm 44)\times {10}^{6}J/\psi$ events collected with the BESIII detector operating at the BEPCII storage ring in 2009, 2012, 2018, and 2019, we perform a search for the reaction ${\mathrm{\Xi }}^{0}n\to \mathrm{\Lambda }\mathrm{\Lambda }X$, where $X$ denotes any additional final particles. Given the highly suppressed phase space for producing extra pions, the $X$ consists of either nothing or a photon, corresponding to the processes ${\mathrm{\Xi }}^{0}n\to \mathrm{\Lambda }\mathrm{\Lambda }$ and ${\mathrm{\Xi }}^{0}n\to \mathrm{\Lambda }{\mathrm{\Sigma }}^0\to \mathrm{\Lambda }\mathrm{\Lambda }\gamma$. The ${\mathrm{\Xi }}^0$ comes from the decay of $J/\psi \to {\mathrm{\Xi }}^0{\overline{\mathrm{\Xi }}}^0$, while the neutron originates from material of the beam pipe. A signal is observed for the first time with a statistical significance of $6.4\sigma$. The cross section for the reaction ${\mathrm{\Xi }}^0+{}^9\mathrm{Be}\to \mathrm{\Lambda }+\mathrm{\Lambda }+X$ is measured to be $(43.6\pm 10.5_{\text{stat}}\pm 11.1_{\text{syst}})\mathrm{mb}$ at $P_{{\mathrm{\Xi }}^0}\approx 0.818\mathrm{GeV}/c$, where the first uncertainty is statistical and the second systematic. No significant $H$-dibaryon signal is observed in the $\mathrm{\Lambda }\mathrm{\Lambda }$ final state.

The in-medium nucleon-nucleon cross section and the cluster production are key ingredients in transport models for heavy-ion collisions. They have been constrained by the comparison of predictions of the AMD transport model to experimental data of ${}^{20}\mathrm{Ne}+{}^{12}\mathrm{C}$ at 50 MeV/nucleon [C. Frosin et al., Phys. Rev. C 107, 044614 (2023)], tuning the related parameters in the framework of a Bayesian inference. Experimental data have been collected with four blocks of the FAZIA setup. A large dataset of observables has been included in the analysis. The prior distribution of the examined parameters was chosen on the basis of the existing literature. The posterior distribution indicates a trend towards a larger number of collisions per event with respect to the previously used simulations.

We study the influence of the nuclear equation of state (EOS) on collective observables—the directed ($v_1$) and elliptic flow ($v_2$) of nucleons and light clusters—in heavy-ion collisions at gigaelectronvolt energies energies using the parton-hadron-quantum-molecular dynamics (PHQMD) approach. A novel development in this work is the inclusion of a momentum-dependent nucleon potential in the PHQMD in addition to the static, density-dependent Skyrme interaction. This enables three distinct EOS scenarios: two static (“soft” and “hard,” differing in compressibility) and a soft, momentum-dependent EOS calibrated to $pA$ elastic scattering data. In PHQMD, clusters form during the entire heavy-ion collision via nucleon interactions and are identified using the minimum spanning tree (MST) algorithm, including additional deuteron production from hadronic kinetic reactions. We find a strong EOS sensitivity in proton and cluster rapidity and $p_T$ distributions: soft and soft momentum-dependent EOS yield similar results, markedly different from the hard EOS. Softening the EOS reduces proton yields at midrapidity while enhancing light-cluster production. The EOS also affects flow observables differently for nucleons and clusters. For protons, a soft momentum-dependent potential increases slightly the magnitude of $v_1$ and $v_2$ relative to the hard EOS, whereas cluster flows are nearly similar. The soft momentum-dependent EOS provides an overall good agreement with experimental data from HADES and FOPI Collaborations while the soft EOS is not in line with the data. A scaling of $v_2$ with cluster mass number $A$ is observed at midrapidity for low $p_T$, which breaks at higher $p_T$. Finally, we examine the sensitivity of flow observables to deuteron production mechanisms. Deuterons formed via MST clustering exhibit different flow patterns from those produced by coalescence at freeze-out, indicating that flow harmonics may help discriminate between cluster formation scenarios.

The formalism of particle number projection on a spatial domain for mean-field wave functions with pairing is revisited to account for the common situation where incomplete, finite-dimensional basis is used. The restriction to a spatial domain implies that the symmetry operators used in projection are always nonunitary and this property requires a specific treatment not considered in traditional approaches. Some deficiencies of previous implementations presented in the literature are highlighted and the correct implementation taking into account the nonunitary character of the symmetry operators in finite-dimensional spaces is presented. It is shown that the present formalism has the right limit in the well-known case of zero pairing, whereas some of the other implementations do not satisfy this basic requirement. By using a simple one-dimensional model, I illustrate the differences in the results obtained with both the correct methods and the incorrect one in the study of particle number distribution probability.