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.

We present a detailed comparison of fusion in ${}^{16}\mathrm{O}+{}^{40,48}\mathrm{Ca}$ within a fully microscopic time-dependent Hartree-Fock framework over sub-, near-, and above-barrier energies. While ${}^{16}\mathrm{O}+{}^{40}\mathrm{Ca}$ fusion cross sections are reproduced within the available experimental energy range, calculations for the neutron-rich ${}^{16}\mathrm{O}+{}^{48}\mathrm{Ca}$ system systematically overestimate the measured near-barrier cross sections. The discrepancy persists across the tested energy density functionals, indicating that it is not tied to a particular parametrization. Analysis of the dynamical interaction potentials reveals an outward shift and softening of the barrier region at the lowest collision energies. These results are then compared to a frozen density description where the barrier modifications are absent and the predicted cross sections are brought closer to experiment. This demonstrates that the observed discrepancy is closely linked to dynamical surface rearrangement and isovector effects, and highlights the sensitivity of low-energy fusion to both the structure and dynamics of neutron-rich nuclei. This suggests that limitations in the isovector sector of conventional Skyrme EDFs in describing the structure of ${}^{48}\mathrm{Ca}$, as highlighted by CREX, are also manifested in the fusion dynamics of the ${}^{16}\mathrm{O}+{}^{48}\mathrm{Ca}$ system.

The nuclei with 50 neutrons that lie between ${}^{78}\mathrm{Ni}$ and ${}^{100}\mathrm{Sn}$ have provided benchmark studies of the nuclear shell model for protons in the $\{0f_{5/2},1p_{3/2},1p_{1/2},0g_{9/2}\}$ model space. New Hamiltonians for this model space have recently been obtained based on valence-space in-medium renormalization-group (VS-IMSRG) methods with two- and three-nucleon interactions. The two-body matrix elements obtained from these ab initio methods served as the starting point for singular value decomposition (SVD) method fits of the TBME to experimental binding energies and excitation energies, resulting in Hamiltonians called p35-i2, p35-i3, and p30-i3. In this paper, magnetic moments, quadrupole moments, $B\left(M1\right)$ and $B\left(E2\right)$ values obtained with these Hamiltonians are presented and compared with experiment. Results obtained from various Hamiltonians are compared to assess the theoretical uncertainties.

Measurements of the ${}^1\mathrm{H}({}^{11}\mathrm{Li},{}^9\mathrm{Li}){}^3\mathrm{H}$ reaction at 6 MeV per nucleon yield differential cross sections for transitions to the ${}^9\mathrm{Li}$ ground and 2.69 and 4.30 MeV excited states. The transition to the 4.30 MeV $(5/2^{-})$ state is observed for the first time in this reaction. Coupled-reaction-channel calculations employing the São Paulo potential and shell-model spectroscopic amplitudes reasonably reproduce the measured angular distributions in magnitude. The agreement highlights the sensitivity of the two-neutron transfer process to the extended matter density distribution and correlated valence neutrons of the halo nucleus ${}^{11}\mathrm{Li}$. Direct two-neutron transfer dominates over sequential mechanisms, underscoring the correlation of the neutrons outside the ${}^9\mathrm{Li}$ core. The results place stringent quantitative constraints on theoretical descriptions of pairing correlations and continuum coupling in weakly bound nuclei.

The properties of neutron-deficient isotopes far from the $\beta$-stability line are crucial for exploring the position of the proton drip line and shell evolution. Nuclei in the vicinity of the doubly magic nucleus ${}^{100}\mathrm{Sn}$ provide a potential access to explore nuclear structure properties. In this work, the temperature dependence of shell corrections on the potential energy surface is incorporated into the dinuclear system (DNS) model. It is observed that the production cross sections of isotopes with $Z=40–54$ in the multinucleon transfer (MNT) reaction ${}^{64}\mathrm{Ni}+{}^{208}\mathrm{Pb}$ are significantly improved, showing better agreement with the experimental data. The production cross sections for isotopes with $Z=46–54$ are calculated using the DNS model, and calculated values are compared with cross sections measured in the laboratories via projectile fragmentation and fusion reactions. The results indicate that MNT reaction is suggested as an available approach for producing new neutron-deficient nuclei near ${}^{100}\mathrm{Sn}$. Furthermore, the cross sections for producing $Z=50–54$ isotopes in the ${}^{58}\mathrm{Ni}+{}^{106}\mathrm{Cd}$, ${}^{56}\mathrm{Ni}+{}^{106}\mathrm{Cd}$, and ${}^{56}\mathrm{Ni}+{}^{112}\mathrm{Sn}$ reactions are also calculated. The effects of the neutron-to-proton ratio $(N/Z)$ in both the projectile and target nuclei, the incident energy, and the shell effects on the production cross sections of new isotopes are investigated as well. It is found that the reaction ${}^{56}\mathrm{Ni}+{}^{106}\mathrm{Cd}$ at an incident energy of $E_{\mathrm{c}.\mathrm{m}.}=232\text{MeV}$ is more favorable for producing neutron-deficient isotopes with $Z=50–54$.

Exceptional points (EPs) are non-Hermitian degeneracies at which two eigenvalues and their eigenvectors coalesce, producing a defective Hamiltonian and a double pole of the $S$-matrix. Using the coupled-channel Gamow shell model with the $\ell =1$ spin-orbit strengths as control parameters, we locate and characterize EPs in ${}^6\mathrm{Li}$, ${}^7\mathrm{Li}$, ${}^7\mathrm{Be}$, and ${}^8\mathrm{Be}$, and we analyze their imprint on energies, widths, phase rigidity, spectroscopic factors, elastic cross sections, survival probabilities, and spectral functions. The signatures of the EP in scattering and time-domain observables are found to be strongly channel-dependent, and threshold effects play a decisive role in determining the accessibility of the EP in parameter space.

I study nonequilibrium cascades in which fragile bound or coherent structures are formed through intermediate states rather than by direct equilibration. Motivated by light-nuclei production in relativistic heavy-ion collisions and by Bose-Einstein condensation in cosmological settings, I analyze such processes within the Schwinger-Keldysh real-time formalism. I show that commonly used rate equations can be understood as a controlled Markovian approximation obtained by integrating out intermediate reservoirs in an underlying multicomponent nonequilibrium dynamics. When the finite lifetime of these reservoirs is retained, non-Markovian memory effects naturally appear, leading to delayed and history-dependent formation dynamics. The associated memory time provides a quantitative criterion for the validity of reduced, rate-based descriptions far from equilibrium. Applying this framework to light-nuclei formation mediated by $\mathrm{\Delta }$ resonances and to condensate formation with localized intermediate structures, I show that equilibrium-like final yields arise as a consequence of finite-lifetime intermediate reservoirs and memory effects, rather than from genuine thermal equilibration.

To consider the dynamic octupole correlations in odd-mass nuclei, an angular-momentum-dependent octupole-vibration core is incorporated into the octupole core-quasiparticle coupling model, and the structure of ${}^{233}\mathrm{Th}$ is studied as a representative example. The calculated positive- and negative-parity bands for both ${}^{233}\mathrm{Th}$ and its core ${}^{232}\mathrm{Th}$ are in good agreement with experimental data, revealing a transition from octupole vibration to static octupole deformation, and confirming the necessity of including the octupole vibration. The electromagnetic transition and probability distributions of spherical single-particle orbitals and core states further elucidate the evolution characteristics of the configuration. This work establishes an effective theoretical approach for studying octupole vibration in odd-mass nuclei.

Neutron-rich nuclei in the region of $Z\approx 28$ and $N\approx 40$ demonstrate a noticeable departure from traditional mean-field nuclear properties through shell evolution effects, display variations in deformation and shape coexistence, and may fall along astrophysical neutron-capture nucleosynthesis pathways. Spectroscopic data on these isotopes provide insight into open questions in low-energy nuclear science, and are becoming more readily available at modern radioactive ion beam facilities. We present the study of the ${}^{71}\mathrm{Fe}\to {}^{71}\mathrm{Co} \beta$ decay, performed using the technique of total absorption spectroscopy. Extracted $\beta$-strength distributions are compared to shell-model calculations to interpret the structure of low-lying levels in ${}^{71}\mathrm{Co}$ and indicate the possibility of shape coexistence. The calculations underestimate the amount of feeding observed at higher excitation energies (and particularly above the neutron separation energy), similarly to some neighboring nuclei in which $\beta$-delayed neutron emission and $\gamma$ decay have been observed to compete. This effect could exert influence on the $\beta$-delayed neutron probability and thus the progression of r-process nucleosynthesis, which is sensitive to such properties.

Nuclear excitation by electron capture (NEEC) is a coupled nuclear-atomic process by which the capture of an electron by an ion into an atomic vacancy results in the excitation of the corresponding nucleus into a higher excited state. To date, there has been only one experimental result, for the nucleus ${}^{93}\mathrm{Mo}$, where a signal indicative of NEEC has been reported. Additional experimental data are vital to provide a testbed for developing theoretical NEEC models to aid in better understanding this phenomenon. In this work, a second NEEC candidate, ${}^{127}\mathrm{Cs}$, was explored using a methodology similar to that in the prior ${}^{93}\mathrm{Mo}$ study. Highly stripped ions of ${}^{127}\mathrm{Cs}$ in its 53.3-$\mu \mathrm{s}$ isomeric state were produced in ${}^9\mathrm{Be}({}^{123}\mathrm{Sb},5n)$ reactions and implanted into target foils. NEEC-signature $\gamma$-ray coincidences were sought using the Digital Gammasphere spectrometer. Although a signature was not observed, upper limits on the NEEC probability were established: 0.17% for implantation into a layered ${}^{27}\mathrm{Al}/{}^{208}\mathrm{Pb}$ target and 0.27% for a single ${}^{208}\mathrm{Pb}$ foil. Theory predicts a yield well below these levels; while the results for ${}^{127}\mathrm{Cs}$ are thus consistent, they ultimately do not provide an explanation that helps resolve the underlying discrepancy between theory and experiment for ${}^{93}\mathrm{Mo}$.

Background: The behavior of fusion excitation functions at deep sub-barrier energies for light systems relevant for astrophysics (e.g., ${}^{12}\mathrm{C} + {}^{12}\mathrm{C}, {}^{12}\mathrm{C} + {}^{16}\mathrm{O}, {}^{16}\mathrm{O} + {}^{16}\mathrm{O}$) is far from being clearly established. This is due to differences between the many data sets, and to the appearance of strong resonance peaks in some cases, as far as the existence and features of fusion hindrance are concerned.

Purpose: To investigate the existence and the threshold of hindrance in the system ${}^{12}\mathrm{C} + {}^{19}\mathrm{F}$, where $Q_{\mathrm{fus}}$ = $+22.95$ MeV, so to clarify the underlying physics by comparing with coupled-channels calculations, and to reliably extrapolate the results to cases of astrophysical relevance such as ${}^{12}\mathrm{C} + {}^{12}\mathrm{C}$ and ${}^{12}\mathrm{C} + {}^{16}\mathrm{O}$.

Methods: ${}^{19}\mathrm{F}$ beams from the XTU Tandem accelerator of LNL were sent onto thin ${}^{12}\mathrm{C}$ targets isotopically enriched to $99.9\%$. The electrostatic beam deflector PISOLO separated the fusion-evaporation residues ER from beam-like particles. Then a $E\text{−}\mathrm{\Delta }E$-time of flight telescope detected and identified the ER.

Results: The fusion cross sections of ${}^{12}\mathrm{C} + {}^{19}\mathrm{F}$ have been measured down to $\approx 76\mu \mathrm{b}$. The logarithmic derivative of the energy-weighted excitation function increases at the lowest energies and reaches the $L_{CS}$ value. Coupled-channels calculations predict significantly lower values, indicating that the hindrance phenomenon shows up in this system. The low-energy cross sections have been fitted using a recently proposed approach.

Conclusions: We compare the low-energy trend of ${}^{12}\mathrm{C} + {}^{19}\mathrm{F}$ with nearby and medium-light systems, using Jiang's phenomenological systematics of the hindrance thresholds, updated with the present data and the behavior of the recent results for ${}^{12}\mathrm{C} + {}^{24,26}\mathrm{Mg}, {}^{28,30}\mathrm{Si}$, and ${}^{16}\mathrm{O} + {}^{48}\mathrm{Ca}$. Overall, we observe that the fit to the measured data, including ${}^{12}\mathrm{C} + {}^{19}\mathrm{F}$ and those systems, leads to an extrapolation to the lighter cases, very close to that obtained from the hindrance model. This is especially true for ${}^{12}\mathrm{C} + {}^{12}\mathrm{C}$, where the several low-energy resonances cause the direct observation of hindrance to be quite challenging.

This investigation compares nonrelativistic and relativistic nucleon-nucleon potentials in the context of proton-deuteron scattering. Conventional NN potentials (e.g., CDBonn, AV18, Nijmegen) rely on the nonrelativistic Schrödinger equation, whereas the Kharkiv potential is intrinsically relativistic. We employ the Coester-Pieper-Serduke (CPS) and Kamada-Glöckle (KG) conversion methods to construct a phenomenological-relativistic potential (PRP) from a realistic NN potential, preserving the deuteron binding energy and phase shifts. Focusing on relativistic effects and not including Coulomb forces to avoid complexity, the solutions are compared by solving relativistic and nonrelativistic Faddeev equations. Calculations of the differential cross section using the relativistic Faddeev equation show that relativistic effects—particularly the deviation at the backward angle—become pronounced at $135\text{MeV}$. The differences in the forward angle were attributed to the characteristics of the Kharkiv potential itself. The reverse transformation of the Kharkiv potential into a pseudononrelativistic potential (PNRP) confirms that the backward-angle relativistic effect increases with energy in the range from $100\text{MeV}$ to $400\text{MeV}$. Comparisons of the polarization observables indicate that relativistic effects, as well as the discrepancy between the CPS and KG transformations, become significant above $300\text{MeV}$. However, for polarization observations below $300\text{MeV}$, the nonrelativistic results from PNRP do not deviate significantly from relativistic calculations.

Within the interacting boson model (IBM), a geometric analysis of transitional nuclei is carried out through angular momentum projection of the intrinsic coherent state. The results indicate that $K$-mixing effects in the calculations are typically negligible, validating the use of $K$-fixed projection for semiclassical analyses of the spin dependence of quadrupole deformation in the IBM. Further analysis indicates that in a rotating transitional system, quadrupole deformation is stretched with increasing angular momentum, providing a geometrically intuitive perspective on the commonly observed Jacobi-type transitions, as exemplified by the case studies of ${}^{160}\mathrm{Gd}$ and ${}^{162}\mathrm{Dy}$. The method is additionally applied to the yrast states of ${}^{170}\mathrm{Os}$ to probe quadrupole deformation changes linked to the observed low-spin $B\left(E2\right)$ anomaly behavior, demonstrating the capability of IBM-based angular momentum projection in interpreting exotic collective phenomena.

An efficient emulator for ab initio calculations of nuclear ground-state properties is developed by integrating the neural-network variational Monte Carlo framework, FeynmanNet, with the eigenvector continuation. It enables the calculation of observables for different Hamiltonians with minimal computational cost, while delivering ground-state energies with errors below $0.5\%$ compared to the full FeynmanNet results. With this emulator, the ground-state energies and charge radii of ${}^{16}\mathrm{O}$, ${}^{15}\mathrm{O}$, ${}^{14}\mathrm{O}$, ${}^{15}\mathrm{N}$, and ${}^{14}\mathrm{C}$ are computed using a nuclear Hamiltonian derived from the leading-order pionless effective field theory, with a large number of different values of low-energy constants (LECs). Then, we perform a global sensitivity analysis of the ground-state energies, charge radii, separation energies of selected nuclei for the three LECs in the Hamiltonian, to identify how each LEC contributes to the variances of these observables. It shows that the two-body LEC in the ${}^3{S}_1$ channel is the most influential LEC governing these nuclear bulk properties. Finally, the correlations among the ground-state energies of ${}^4\mathrm{He}$, ${}^{12}\mathrm{C}$, and ${}^{16}\mathrm{O}$ are investigated by varying the LECs in the Hamiltonian. The analysis reveals that the experimental ground-state energies of ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ cannot be reproduced simultaneously by varying the LECs in the leading-order pionless Hamiltonian. This suggests that additional ingredients in the leading-order Hamiltonian are required to improve its description of light nuclei. The present work establishes an efficient framework for global sensitivity analysis and uncertainty quantification in the quantum Monte Carlo calculations for light and medium-mass nuclei.