This paper reports on the first complete shell-model description of low-lying structures of ${}^{254}\mathrm{No}$. Employing the Kuo-Herling effective interaction, the calculations are performed using the discrete nonorthogonal shell model recently implemented within the angular-momentum variation after projection applied on nonaxial wave functions. Our calculations show a striking agreement with the experimentally known spectroscopy: the yrast band, the $8^{-}$ ($K=8$), $3^{+}$ ($K=3$), and ${10}^{+}$ ($K=10$) isomers together with associated $K$ bands. We reproduce the recently measured Gallagher-Moszkowski splitting between the $3^{+}(K=3$) and $4^{+}$ ($K=4$) bandheads. We predict the appearance of a second $0^{+}$ state in excellent agreement with recent observations. In addition, we systematically examine the ground state spectra and the dipole and spectroscopic quadrupole moments of even-even, odd-even, odd-odd nuclei from $A=251$ to $A=256$, which are favorably reproduced. The present description of ${}^{254}\mathrm{No}$ shows the ability of the shell model framework to describe the low-lying properties for such an exotic nucleus at the frontier of modern experimental nuclear physics research.

In this first-of-its-kind survey conducted on heavy and deformed nuclei in the actinide region of the nuclear chart, we have charted nuclear ground state properties predicted by Fayans energy density functionals (EDFs), focusing in particularly on octupole deformability. Compared to earlier studies with Skyrme-based EDFs, we found a similar region of octupole deformed nuclei. Moreover, Fayans EDFs were found to provide accurate predictions for various ground state properties, when compared to experimental data. Comparison to Skyrme-based EDFs shows similar trends in various nuclear properties.

Properties of isomeric states and the deexcitation paths to the ground state have been observed in ${}^{165}\mathrm{W}$ and ${}^{169}\mathrm{W}$ nuclei in experiments employing fusion-evaporation reactions at the Accelerator Laboratory of the University of Jyväskylä, Finland. The $(13/2^{+})$ isomeric state in ${}^{165}\mathrm{W}$ was measured to have a half-life of $7.4\left(2\right)$µs and an excitation energy of 301.4(3) keV, while in ${}^{169}\mathrm{W}$, the $J^{\pi }=(9/2^{+})$ isomeric state at 127.2(3) keV has $t_{1/2}=7.4\left(5\right)$µs. The observed hindrance factors are 6.9(2) for the $M2$ deexciting transition in ${}^{165}\mathrm{W}$ and $2.29\left(15\right)\times {10}^6$ for the $E1$ deexciting transition in ${}^{169}\mathrm{W}$, of which the former is a typical value in this region, while the latter is an order of magnitude larger than most other similar cases. The excited- and ground-state spin assignments are discussed.

A study of the $N=89$ odd-odd nucleus ${}^{150}\mathrm{Pm}$ with the ${}^{152}\mathrm{Sm}(d,\alpha )$ reaction at 18 MeV incident energy is presented. A distorted-wave Born approximation (DWBA) analysis of measured angular distributions has been performed for 48 states observed in this nucleus up to $E_x\approx 1.4$ MeV, yielding information on their possible spin and parity values. Albeit not unique due to inherent ambiguities of the DWBA analysis, these assignments are the only ones existing now for this nucleus, for which $J^{\pi }$ values were previously proposed for only two states. A comparison of the observed states is made with theoretical calculations, performed with the Interacting boson-fermion-Fermion Model-2, and the Shell Model, respectively. These results are a first step to a better understanding of the structure of the odd-odd nuclei around the shape phase transition critical point at $N=90$.

An yrast, $J^{\pi }=5^{-}$, spin-trap isomer has been previously identified in ${}^{32}\mathrm{Si}$. The isomeric state decays predominantly via a hindered $E3$ transition [$B$($E3$) = 0.0841(10) W.u.], bypassing a nearby $E2$ decay path to the first excited $3^{-}$ level. The single-neutron aspects of these negative-parity levels were investigated via the ${}^{31}\mathrm{Si}\left(d,p\right){}^{32}\mathrm{Si}$ reaction at 9.6 MeV/u using HELIOS and the ATLAS in-flight facility. The $5^{-}$ state appears as a dominant $\ell =3$ transfer with a relatively large spectroscopic factor, confirming its single-particle $\nu 0f_{7/2}$ character. The yrast $3^{-}$ level had a reduced $\ell =3$ spectroscopic factor of approximately 0.44 compared with that of the $5_1^{-}$ level. This is similar to the situation observed in nearby ${}^{34}\mathrm{S}$, which by contrast has a measured $B$($E2,5^{-}\to 3^{-}$) transition strength closer to 1 W.u. It has been concluded that the hindrance of the $5_1^{-}\to 3_1^{-}$ transition in ${}^{32}\mathrm{Si}$ is not primarily due to the differing overlaps in the neutron structure. Instead, the lack of participation by both the protons and the neutrons in the transition is proposed as the transition-strength-reduction mechanism.

We quantify to what degree the QCD matter created in high-energy oxygen-oxygen ($\mathrm{O}+\mathrm{O}$) collisions at $\sqrt{s_{NN}}=5.36$ TeV reaches a locally equilibrated state. For this purpose, we employ a novel framework based on the core-corona picture that describes the dynamics of both locally equilibrated fluids (the core) and nonequilibrium particles (the corona). Contributions from the core become larger than those from the corona above charged-particle multiplicity at midrapidity, ${\langle d{N}_{\mathrm{ch}}/d\eta \rangle }_{\left|\eta \right|<0.5}\approx 20$. We also find that non-negligible contributions from the corona still remain even in central $\mathrm{O}+\mathrm{O}$ collisions. The yield ratios of strange baryons to charged pions exhibit an increasing behavior with increasing multiplicity at midrapidity. However, these ratios are smaller than those obtained when assuming that QCD matter has reached complete chemical equilibrium. These results demonstrate that a purely hydrodynamic approach is insufficient and that the inclusion of a corona component is essential for describing the dynamics of intermediate-size systems such as $\mathrm{O}+\mathrm{O}$ collisions.

An outstanding puzzle in the structure of very heavy nuclei lies in the rotation response of deformed transuranic isotopes. While the rotation alignment of pairs of $i_{13/2}$ protons is ubiquitous and well understood, observing the analogous alignment of the $j_{15/2}$ neutrons has been elusive. In this work we present a new quantitative analysis approach: from their moments of inertia as a function of frequency, we compare the alignments of rotational bands with both “low” and high-$j$ intrinsic structures in the $N=151$ isotones of Pu, Cm, Cf, and No, thereby distinguishing between the alignments of neutron versus proton pairs through “blocking” effects. In this way, the alignment of $j_{15/2}$ neutrons can be clearly identified for the first time. The protons and neutrons begin aligning at a very similar frequency. The contribution of $j_{15/2}$ neutrons to the total alignment is found to grow with increasing $Z$ compared to $i_{13/2}$ protons. To explain these observations, it is necessary to adopt a self-consistent set of single-particle energies corresponding to the nuclear shape that minimizes the mass. The shape description needs to include high-order deformations up to at least ${\beta }_6$.

Employing the relativistic continuum Hartree-Bogoliubov (RCHB) theory with intrinsic electromagnetic structure corrections, this work primarily investigates the charge properties of halo nuclei along the Ne and P isotopic chains. Our results characterize halo nuclei by an extended tail in the charge density and distinct signatures in the charge form factors at low momentum transfer. Moreover, the higher-order radial moments of nuclear charge density, particularly the eighth moment, exhibit pronounced oscillations, serving as a key indicator of the neutron halo structure. These special features in nuclear charge distributions will serve as key references for identifying halo nuclei.

One- and two-quasiparticle spectra are calculated in superheavy nuclei ${}^{293}119$ and ${}^{294,296,298}119$, respectively, within the two-center shell model. Possible $\alpha$-decay chains of those 119 nuclei are analyzed. The role of isomeric states in the $\alpha$-decay spectra is considered. The calculated $Q_{\alpha }$ energies are compared with available experimental data.

Weak Gamow-Teller (GT) responses for low-lying states in ${}^{71}\mathrm{Ga}$ are crucial for studying low-energy solar neutrinos and the Ga anomaly, i.e., the possible transition to the sterile state. The structures for the ground state, the first excited state, and the second excited state are evaluated for the first time using the experimental electron capture rates, the experimental charge exchange reaction (CER) rates corrected for the tensor-interaction effect, and the theoretical interacting shell model (ISM) calculations. On the basis of these experimental and theoretical results, the neutrino responses for them are evaluated. The contributions from the two excited states to the solar and ${}^{51}\mathrm{Cr}$ neutrinos are found to be $4.2\pm 1.2\%$ of that for the ground state. This is slightly larger than the ISM values but a little smaller than the CER values without corrections for the tensor interaction effect. The Ga anomaly is far beyond the uncertainty of the obtained nuclear responses. The present work shows for the first time the way to evaluate the tensor contributions on the basis of the EC/$\beta$ and CER experiments and the ISM calculations.

The relativistic Hartree-Fock-Bogoliubov (RHFB) framework has been extended to incorporate axially symmetric octupole deformation, leading to the development of the O-RHFB model. This model is applied to analyze the onset of octupole deformation in ${}^{228}\mathrm{Th}$ and the proton-drip-line candidate ${}^{114}\mathrm{Ba}$ using the RHF Lagrangian PKA1 and the relativistic mean field (RMF) parameter set DD-ME2. Both interactions successfully reproduce stable octupole and quadruple deformations in the ground state of ${}^{228}\mathrm{Th}$. For ${}^{114}\mathrm{Ba}$, however, PKA1 yields a relatively soft octupole deformation, in contrast to the stable one predicted by DD-ME2. From the perspective of pseudospin symmetry (PSS), it is shown that the direct development of octupole deformation from a spherical configuration is unfavorable in both nuclei, and its onset is inevitably accompanied by significant quadruple deformation. Further analysis of PSS restoration in spherical configurations reveals a notable model discrepancy rooted in the description of nuclear binding. In particular, the exchange degrees of freedom associated with the $\pi$-pseudovactor and $\rho$-tensor couplings in PKA1 are found to play an essential role in determining nuclear binding and, consequently, in shaping the octupole-deformed characteristics of both ${}^{228}\mathrm{Th}$ and ${}^{114}\mathrm{Ba}$.

A recurring question in continuum-discretized coupled-channels calculations is which continuum channels carry the breakup coupling, both to interpret the reaction and to decide which channels a model space can safely omit. The standard answer is bin deletion: remove a channel, re-solve the coupled equations, and read the change in the elastic $S$ matrix. We show that this cannot isolate an individual channel's contribution. Deleting a channel forces the surviving model space to reorganize, with the neighboring bins rerouting through the off-diagonal Green's function, so the recorded change mixes the channel's own effect with the readjustment of all the others. Working instead from the channel-resolved Feshbach dynamic polarization potential (DPP), whose full-coupling Green's function is a fixed reference shared by every channel, we define an exclusion that removes one channel while holding that reference fixed, returning its contribution to the intact system. The two operations disagree on which continuum bins matter most, for $d+{}^{58}\mathrm{Ni}$ at 21.6 MeV even sending the intrinsically leading bin to last place under deletion. The DPP further separates each channel's action into a direct path, virtual excitation and return, and a bridge path, relayed through neighboring bins, a split deletion cannot make; it shows the bins act on the elastic channel mainly as bridges, robustly across angular momentum, and that it is this bridge coupling that reorganizes under deletion. A deletion-based channel importance is therefore best read as the truncated calculation's sensitivity to a channel's removal, not as the channel's intrinsic coupling strength.

Heavy-ion collisions produce final states with thousands to tens of thousands of particles, making their simulation among the most computationally intensive tasks in high-energy nuclear physics. We present a fast, high-fidelity generative model for heavy-ion events based on a score-driven diffusion process and the point-edge transformer architecture within the OmniLearn framework. A two-stage training strategy is performed: Stage 1 trains on lower-multiplicity O-O collisions, allowing the model to learn a stable event-and-particles representation; this is followed in Stage 2 by fine tuning on challenging high-multiplicity Pb-Pb collisions. We benchmark the generator with a broad set of closure checks, including agreement of event- and particle-level observables in one and two dimensions, flow consistency reconstructed from the generated particles, end-to-end jet finding with FastJet including key jet and substructure observables, and a classifier-based application to quantify the sample fidelity. The results are promising, showing that a compact generative model can produce realistic, high-multiplicity heavy-ion events, at a level that makes local-scale generation for heavy-ion collisions at high energies a practical goal.

The Nab (Neutron a b) experiment is designed to measure the beta-antineutrino angular correlation in free neutron $\beta$ decay with an ultimate precision goal of 0.1%, providing input for tests of Cabibbo-Kobayashi-Maskawa matrix unitarity. This measurement is performed via detection of electrons and protons in delayed coincidence using custom large-area segmented silicon detectors. We present the characterization of one such detector system to establish the proton energy and timing response, using a dedicated proton accelerator. The detected proton peak was studied for 25, 30, and 35 keV incident protons on a set of detector segments and multiple cooling cycles over a one-year period. Ionization losses were consistent with models of the detector dead layer with thicknesses less than 100 nm. The detected proton peak was stable within the uncertainty from energy calibration (0.25 keV). The rise times of detector pulses from ${}^{109}\mathrm{Cd}$ and ${}^{113}\mathrm{Sn}$ conversion electron sources were used to extract the impurity density profile and establish a precise model for the detector timing response. The observed impurity density profile varied from $(2\pm 2)\times {10}^9/{\mathrm{cm}}^3$ at the center to $(26\pm 2)\times {10}^9/{\mathrm{cm}}^3$ at the edge. This impurity density profile was then used to characterize systematic effects in proton time-of-flight measurements due to detector pulse-shape effects; the resultant proton timing systematic uncertainties were below 0.3 ns, which is sufficient for the Nab experiment.

In this work, we use the $\beta$-Oslo method to investigate the nuclear level density and $\gamma$-ray strength function of ${}^{97}\mathrm{Zr}$. The measurement was performed using the Summing NaI detector at Argonne National Laboratory. The nucleus of interest was populated via the $\beta$ decay of ${}^{97}\mathrm{Y}$. The extracted $\gamma$-ray strength function exhibits a clear low-energy enhancement. The evolution of this low-energy enhancement in neutron-rich isotopes is of particular interest due to its potential impact on ($n,\gamma$) reaction rates. We also use the extracted nuclear level density and $\gamma$-ray strength function to determine the ${}^{96}\mathrm{Zr}(n,\gamma ){}^{97}\mathrm{Zr}$ reaction cross section, which reasonably agrees with the existing direct measurements. This agreement provides further support for the $\beta$-Oslo method as a reliable approach for estimating neutron-capture reaction rates, especially for nuclei where direct measurements are not available.

Sub-barrier fusion reactions are ideal for probing the effects of pairing correlations on simultaneous neutron transfer. Previous calculations using the BCS approximation showed an enhancement of pair transfer, relative to treatments with no pairing, but failed to reproduce the observed enhancement factor between one- and two-neutron transfer probabilities. This work aims to microscopically investigate the dynamics of ${}^{40,48}\mathrm{Ca}+{}^{96}\mathrm{Zr}$ head-on collisions below the Coulomb barrier, focusing on the role of pairing correlations in neutron transfer. We employ time-dependent energy density functional theory extended to superfluid systems, time-dependent superfluid local density approximation (TDSLDA). Transfer probabilities, including contributions to specific $K$-angular momentum projections, are extracted using projection operators and compared to results from calculations without pairing. Our calculations show that pairing is correlated to the dynamic deformability of the nucleus, which influences mean neutron transfer in sub-barrier reactions. We also show that TDSLDA reproduces the experimentally observed enhancement factor by significantly increasing the probability of transferring a neutron pair in the $K=0$ spin channel. These results confirm the strong influence of pairing and structure on sub-barrier multinucleon transfer, and demonstrate that TDSLDA provides a reliable microscopic framework for describing the interplay between nuclear superfluidity and reaction dynamics.

As a fundamental property of atomic nuclei, the nuclear charge radius reveals rich structural characteristics such as shell evolution and pairing correlation. Previously, machine learning strategies have been employed in this domain by typically utilizing the residuals between experimental measurements and theoretical predictions as training input to optimize calculations and significantly improve accuracy. In contrast, the present study focuses on the local variations in the nuclear charge radii to investigate the underlying shell structure. Specifically, we adopt a purely data-driven approach, directly utilizing raw radius data as training samples in an attempt to delineate the evolutionary trajectories of the shell structure. In general, the root mean square deviation of the entire dataset between the experimental and predicted values can be reduced to 0.0134 fm using the Extreme Gradient Boosting (XGBoost) algorithm. Encouraged by this, we partitioned the isotopic chains into various $N$, using the majority of the chains alongside the bulk data for training, and reserving the remainder for validation. This approach provides clear insights into shell evolution by successfully capturing structural kinks, specifically slope discontinuities at magic numbers $N=28,50,$ and 82. Furthermore, the odd-even staggering, governed by the interplay of nuclear deformation and pairing correlations, is well reproduced, as exemplified in the barium isotopic chain. These findings highlight the capability of the machine learning algorithm to implicitly learn the microscopic mechanisms of the nuclear structure from the minimalist feature space. Ultimately, this establishes a novel and robust paradigm for investigating exotic nuclei far from the line of stability and constraining the nuclear equation of state.

The PHENIX experiment at the Relativistic Heavy Ion Collider measured the second Fourier component $v_2$ of the direct-photon azimuthal anisotropy at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$. The results are presented in 10% wide bins of collision centrality and cover the transverse-momentum range of $1<p_T<20\mathrm{GeV}/c$, and are in quantitative agreement with findings published earlier, but provide better granularity and higher $p_T$ reach. Above a $p_T$ of $8–10\mathrm{GeV}/c$, where hard scattering dominates the direct-photon production, $v_2$ is consistent with zero. At lower $p_T$, direct photon $v_2$ as a function of $p_T$ is comparable to the ${\pi }^0$ anisotropy over all centralities, albeit being overall slightly smaller. The results are compared to recent theory calculations that include, in addition to thermal radiation from the quark-gluon plasma and hadron gas, sources of photons from preequilibrium, strong magnetic fields, or radiative hadronization. While the newer theoretical calculations describe the data better than previous models, none of them alone can fully explain the results.

The collective expansion and hydrodynamic evolution in heavy-ion collisions is well established. However, whether femtometer-scale droplets of quark-gluon plasma (QGP) are produced in small systems at high energies remains a fundamental open question. Analysis of Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, Xe-Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV, and O-O collisions at $\sqrt{s_{NN}}$ = 5.36 TeV using EPOS4 is reported to make predictions and postdictions. The results are compared with ALICE data for Pb-Pb and Xe-Xe collisions. Charged particle multiplicity $(\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta )$ and transverse-momentum $\left(p_{\mathrm{T}}\right)$ spectra for pions $\left({\pi }^{\pm }\right)$, kaons $\left(K^{\pm }\right)$, and protons $\left[p\left(\overline{p}\right)\right]$ are studied. The inclusion of a hadronic afterburner, UrQMD (Ultrarelativistic Quantum Molecular Dynamics) is found to be necessary to correctly describe baryon yields. $p_{\mathrm{T}}$ fluctuations are also studied via normalized $p_{\mathrm{T}}$ correlator, $\sqrt{\langle \langle \mathrm{\Delta }{p}_{\mathrm{T},i}\mathrm{\Delta }{p}_{\mathrm{T},j}\rangle \rangle }/\langle \langle p_{\mathrm{T}}\rangle \rangle$. Lastly, anisotropic flow harmonics $(v_2\left\{2\right\},$ $v_3\left\{2\right\})$ are computed as a function of $p_{\mathrm{T}}$ and centrality. Since EPOS4 has not been extensively studied for flow observables, this study thereby provides a nontrivial assessment of its collective dynamics. The results are compared with experiment wherever data are available. Taken together, this study provides a unified description of soft observables from Pb-Pb through Xe-Xe down to O-O and offers quantitative guidance on how such collisions may inform of the properties of the QGP.

Background: Type I x-ray bursts (XRBs) are energetic stellar explosions that occur on the surface of a neutron star in an accreting binary system with a low-mass H/He-rich companion. The rate of the ${}^{34}\mathrm{Ar}(\alpha ,p){}^{37}\mathrm{K}$ reaction may influence features of the light curve that results from the underlying thermonuclear runaway, as shown in recent XRB stellar modeling studies.

Purpose: To reduce the uncertainty of the rate of this reaction, properties of resonances in the compound nucleus ${}^{38}\mathrm{Ca}$, such as resonance energies, spins, and particle widths, must be well constrained.

Method: This work discusses a study of resonances in the ${}^{38}\mathrm{Ca}$ compound nucleus produced in the ${}^{34}\mathrm{Ar}(\alpha ,p)$ reaction. The experiment was performed at the National Superconducting Cyclotron Laboratory, with the ReA3 facility by measuring proton scattering using an unstable ${}^{37}\mathrm{K}$ beam. The kinematics were designed specifically to identify and characterize resonances in the Gamow energy window for the temperature regime relevant to XRBs.

Results: The spins and proton widths of newly identified and previously known states in ${}^{38}\mathrm{Ca}$ in the energy region of interest for the ${}^{34}\mathrm{Ar}(\alpha ,p){}^{37}\mathrm{K}$ reaction have been constrained through an R-matrix analysis of the scattering data.

Conclusions: Using these constraints, a newly estimated rate is applied to an XRB model built using Modules for Experiments in Stellar Astrophysics, to examine its impact on observables, including the light curve. It is found that the newly determined reaction rate does not substantially affect the features of the light curve.