Deuteron breakup in collision with a ${}^{24}\mathrm{Mg}$ nucleus is studied using rigorous three-body scattering equations, extended to include also the excitation of the nucleus. Predictions based on local and nonlocal nucleon-nucleus optical potentials with rotational quadrupole deformation enabling the excitation of the ${}^{24}\mathrm{Mg}\left(2^{+}\right)$ state are compared. The nonlocality effect is less pronounced than in the deuteron inelastic scattering ${}^{24}\mathrm{Mg}(d,d^{\prime })$ at the same energies, and manifests itself quite differently for semi-inclusive differential cross sections of elastic and inelastic breakup.

We have investigated the performance of anisotropic flows $\langle v_n^2\rangle$, transverse momentum fluctuations $\langle \delta p_T^2\rangle$, and their correlations $\langle v_n^2\delta p_T\rangle$ in central collisions at relativistic energies as probes of deformation parameters ${\beta }_n$ of colliding nuclei, if these nuclei are light nuclei with large ${\beta }_n$ and different configurations of $\alpha$ clusters. The effects from higher-order ${\beta }_n$ terms are illustrated by derived relations based on the overlap of two nuclei with uniform density distributions and by dynamic simulations of collisions of heavy nuclei whose density distributions are of a deformed Woods-Saxon (WS) form. While the linear relations between ${\beta }_n^2, \langle v_n^2\rangle$, and $\langle \delta p_T^2\rangle$ and that between ${\beta }_n^3$ and $\langle v_n^2\delta p_T\rangle$ can be violated for extremely large ${\beta }_n$, they are mostly valid for realistic values of ${\beta }_n$, as long as the density distribution of colliding nuclei can be described by a deformed WS form. However, these linear relations are generally not valid with more realistic density distributions of light nuclei with $\alpha$ clusters, and the amount of deviation depends on the detailed $\alpha$-cluster configurations. Care must be taken when one tries to extract the deformation of light nuclei, and specific probes for $\alpha$-cluster structures in these nuclei are very much needed.

The ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction, an important component of stellar helium burning, has a key role in nuclear astrophysics. It has significant impact on the evolution and final state of heavy to low mass stars, maximum mass of stellar formed black holes and also shapes the elemental abundances resulting from nucleosynthesis in such stars. Providing a reliable estimate for the energy dependence of this reaction at stellar helium burning temperatures has been a longstanding and important goal. In this work, we study the role of potential new $E1$ and $E2$ measurements of the ${}^{16}\mathrm{O}(e,e^{\prime }\alpha ){}^{12}\mathrm{C}$ reaction in reducing the overall uncertainty in the astrophysical $S$ factor for the ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}E1$ and $E2$ ground state capture extrapolated to a stellar energy of 300 keV. A multilevel $R$-matrix analysis is used to make extrapolations of the $S_{E1}$(300 keV) and $S_{E2}$(300 keV) factors for the ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction from existing ground state capture data. Bayesian analysis is used to quantify the uncertainties in the extrapolations for both the existing data alone and also when possible new experimental data are included. In particular, we consider a new experiment that would make use of a high-intensity low-energy electron beam that impinges on a windowless oxygen gas target as a means to determine the total $E1$ and $E2$ ground state cross sections for this reaction. We find that the new data could significantly reduce the $S\left(300\right)$ uncertainties. Splitting the new data into high and low energy regions shows that both low and high energy data are effective in reducing the uncertainty.

Low-lying excited states in ${}^{93}\mathrm{Tc}$ and ${}^{94}\mathrm{Ru}$ were populated using the two fusion-evaporation reactions ${}^{90}\mathrm{Zr}({}^6\mathrm{Li},3n){}^{93}\mathrm{Tc}$ and ${}^{92}\mathrm{Mo}(\alpha ,2n){}^{94}\mathrm{Ru}$ at the Cologne FN Tandem accelerator and their lifetimes were measured using a hybrid setup of high-purity germanium and fast cerium doped lanthanum bromide detectors for $\gamma \text{−}\gamma$ fast-timing. The measured lifetimes fill gaps in the experimental data for electromagnetic transition probabilities $B\left(\sigma \lambda \right)$ along the $N=50$ isotonic chain and provide more insight for ambiguous cases, such as the lifetime of the $4_1^{+}$ state in ${}^{94}\mathrm{Ru}$. The experimental data are compared with theoretical $B\left(E2\right)$ values from a single-$j$ approximation, with state-dependent effective charges derived from ${}^{92}\mathrm{Mo}$ and with the results from shell-model calculations performed using the SR88MHJM interaction in the $\pi (1p_{1/2},0g_{9/2})$ model space.

Atomic masses are a foundational quantity in our understanding of nuclear structure, astrophysics, and fundamental symmetries. The longstanding goal of creating a predictive global model for the binding energy of a nucleus remains a significant challenge, however, and prompts the need for precise measurements of atomic masses to serve as anchor points for model developments. We present precise mass measurements of neutron-rich Ru and Pd isotopes performed at the Californium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory using the Canadian Penning Trap mass spectrometer. The masses of ${}^{108}\mathrm{Ru}, {}^{110}\mathrm{Ru}$, and ${}^{116}\mathrm{Pd}$ were measured to a relative mass precision $\delta m/m\approx {10}^{-8}$ via the phase-imaging ion-cyclotron-resonance technique, and represent an improvement of approximately an order of magnitude over previous measurements. These mass data were used in conjunction with the physically interpretable machine learning (PIML) model, which uses a mixture density neural network to model mass excesses via a mixture of Gaussian distributions. The effects of our new mass data on a Bayesian-updating of a PIML model are presented.

We use deep neural networks (DNNs) to obtain the properties of partons in terms of an off-shell quasiparticle description. We aim to infer masses and widths of quasigluons, up/down, and strange (anti)quarks using constraints on the macroscopic thermodynamic observables obtained by the first-principles lattice QCD (lQCD) calculations. In this study we use three independent dimensionless thermodynamic observables from lQCD for minimization as the ratio of entropy density to temperature $s/T^3$, baryon susceptibility ${\chi }_2^B$, and strangeness susceptibility ${\chi }_2^S$. First, we train our DNN using the DQPM (dynamical quasiparticle model) ansatz for the masses and widths. Furthermore, we use the DNN capabilities to generalize this ansatz, to evaluate which quasiparticle masses and widths are desirable to describe different thermodynamic functions simultaneously. To evaluate consistently the microscopic properties obtained by the DNN in the case of off-shell quarks and gluons, we compute transport coefficients using the spectral function within the Kubo-Zubarev formalism in different setups. In particular, we make a comprehensive comparison in the case of the dimensionless ratios of shear viscosity over entropy density $\eta /s$, and electric conductivity over temperature ${\sigma }_Q/T$, which provide additional constraints for the parameter generalization of the considered model cases. We present the parameter settings found by the DNN which can improve the quasiparticle description of lQCD data on the susceptibility and electric conductivity of strange quarks.

The $\text{D}(p,\gamma ){}^3\mathrm{He}$ reaction, where ‘D’ denotes ‘${}^2\mathrm{H}$’, is of primary importance in cosmology and nuclear physics since it offers a unique opportunity to test predictions based on the description of nuclear interactions. We present a novel approach to extract the angular distribution of the photons emitted by the $\text{D}(p,\gamma ){}^3\mathrm{He}$ reaction inferred from the shape of the experimental $\gamma$ spectra. The measurement was performed in the Gran Sasso Laboratories by the LUNA collaboration. By using a HPGe detector faced to an extended deuterium gas target, it was possible to derive the angular distribution in the 30–280 keV kinetic energy range and to compare the results with recent ab initio predictions.

Electromagnetic multipole responses are key inputs to model the structure, decay, and reactions of atomic nuclei. With the introduction of the finite amplitude method (FAM), large-scale calculations of the nuclear linear response in heavy deformed nuclei have become possible. This work provides a detailed study of multipole responses in actinide nuclei with Skyrme energy density functionals. We quantify both systematic and statistical uncertainties induced by the functional parametrization in FAM calculations. We also extend the FAM formalism to perform blocking calculations with the equal filling approximation for odd-mass and odd-odd nuclei, and analyze the impact of blocking configurations on the response. By examining the entire plutonium isotopic chain from the proton to the neutron drip line, we find a large variability of the response with the neutron number and study how it correlates with the deformation of the nuclear ground state.

The model uncertainties in predictions of nucleon separation energies are investigated based on four nuclear mass models and the measured masses of mirror nuclei. It is found that the discrepancies between model predictions and experimental data for the proton separation energies of a nucleus have a linear relationship with those for the neutron separation energies of its mirror nucleus. With the linear mirror corrections being considered, the root-mean-square deviation of model predictions is reduced by more than $56\%$ for one-proton separation energies, and more than $47\%$ for two-proton separation energies. Simultaneously, ${}^{34}\mathrm{Ca}, {}^{38}\mathrm{Ti}$, and ${}^{62}\mathrm{Se}$ are suggested as the possible ground-state two-proton decay nuclei according to the predicted separation energies and half-lives.

Background: Electric and magnetic dipole strengths in nuclei at excitation energies well below the giant resonance region are of interest for a variety of nuclear structure problems including a possible electric dipole toroidal mode or the quenching of spin-isospin flip modes.

Purpose: The aim of the present work is a state-by-state analysis of possible $E1$ and $M1$ transitions in ${}^{58}\mathrm{Ni}$ with a high-resolution $(p,p^{\prime })$ experiment at 295 MeV and very forward angles including $0^{\circ }$ and a comparison to results from studies of the dipole strength with the $(\gamma ,{\gamma }^{\prime })$ and $(e,e^{\prime })$ reactions.

Methods: The $E1$ and $M1$ cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis (MDA). They are converted to reduced $E1$ and spin $M1$ transition strengths using the virtual photon method of relativistic Coulomb excitation and the unit cross-section method, respectively. The experimental $M1$ strength distribution is compared to large-scale shell-model calculations with the effective GXPF1A and KB3G interactions.

Results: In total, 11 $E1$ and 26 $M1$ transitions could be uniquely identified in the excitation energy region $6–13$ MeV. In addition, 22 dipole transitions with preference for either $E1$ or $M1$ multipolarity and 57 transitions with uncertain multipolarity were found. Despite the high level density good agreement is obtained for the deduced excitation energies of $J=1$ states in the three types of experiments indicating that the same states are excited. The $B\left(E1\right)$ and $B\left(M1\right)$ strengths deduced in the $(\gamma ,{\gamma }^{\prime })$ experiments are systematically smaller than in the present work because of the lack of information on branching ratios to lower-lying excited states and the competition of particle emission. Fair agreement with the $B\left(M1\right)$ strengths extracted from the $(e,e^{\prime })$ data is obtained after removal of $E1$ transitions uniquely assigned in the present work belonging to a low-energy toroidal mode with unusual properties mimicking $M1$ excitations in electron scattering. The shell-model calculations provide a good description of the isospin splitting and the running sum of the $M1$ strength. A quenching factor 0.74 for the spin-isospin part of the $M1$ operator is needed to attain quantitative agreement with the data.

Conclusions: High-resolution forward-angle inelastic proton scattering experiments at beam energies of about 300 MeV are a highly selective tool for an extraction of resolved $E1$ and $M1$ strength distributions in medium-mass nuclei. Fair agreement with results from electron scattering experiments is obtained indicating a dominance of spin contributions to the $M1$ strength. Shell-model calculations are in good agreement with gross properties of the $M1$ strength distribution when a quenching factor for the spin-isospin part comparable to the one needed for a description of Gamow-Teller (GT) strength is included.

Relativistic heavy ion collisions provide a unique opportunity to study the shape of colliding nuclei, even up to higher-order multipole deformations. In this work, several observables that are sensitive to quadrupole and hexadecapole deformations of uranium-238 in relativistic $\text{U}+\text{U}$ collisions have been systematically investigated with a multi-phase transport model. We find that the flow harmonic $v_2$, the $v_2$ and mean transverse momentum correlation, and the three-particle asymmetry cumulant ${\mathrm{ac}}_2\left\{3\right\}$ are sensitive to nuclear quadrupole deformation, while ${\mathrm{ac}}_2\left\{3\right\}$ and nonlinear response coefficient ${\chi }_{4,22}$ are sensitive to nuclear hexadecapole deformation. Our results from transport model studies are in qualitative agreement with previous hydrodynamic studies. The results indicate that the uncertainties of the hexadecapole deformation of uranium on the quadrupole deformation determination can be reduced by the abundance of correlation observables provided by the relativistic heavy ion collisions.

Background: Asymmetric mass splits observed in the extremely neutron-deficient ($1.15\le N/Z\le 1.55$) lead-island isotopes brought much interest for the scientific community to explore this region. Although several experiments have been performed adopting $\beta$-delayed fission and heavy-ion induced reactions, the role of shell effects associated with asymmetric fission is still not fully understood.

Purpose: This article demonstrates the fission fragment mass distributions and associated fission fragment properties of ${}^{186}\mathrm{Pt}$, populated via fusion of ${}^{28}\mathrm{Si}$ with ${}^{158}\mathrm{Gd}$, at three excitation energies ($E^{*}\mathrm{s}$). Further, a comparison of experimental mass distributions with the theoretical results has been carried out to test their prediction efficiency.

Method: Thin layer of ${}^{158}\mathrm{Gd}$ (${}^{158}\mathrm{Gd}_2{\mathrm{O}}_3$) backed by the carbon was bombarded by ${}^{28}\mathrm{Si}$ ions within 120–140 MeV laboratory energy. Time-of-flight information, provided by the two symmetrically placed multiwire proportional counters having an area of 200 ${\mathrm{cm}}^2$, was utilized to get the velocities, which were further used to estimate the fission fragment mass and kinetic energy distributions.

Results: A single Gaussian could not satisfactorily fit the flat-topped mass distribution at each excitation energy. Later, the two- and three-Gaussian fits efficiently reproduced the distributions, signifying the crucial role of the quadrupole deformed ($Z\approx$ 34, 36, 42, 44, and 46) shell gaps in deciding the fate of compound nucleus's disintegration. No signature of the quasifission process has been observed in this study. Moreover, an increment in the symmetric contribution with increasing $E^{*}$ is spotted experimentally as well as theoretically for the present system. Further, a comparison with the nearby Pt isotopes revealed the symmetric contributions decrease with decreasing neutron number. To some extent, GEneral Fission (GEF) model is found to predict the fragment properties of the present system.

Conclusions: The structure observed in the middle section of the mass distribution confirms the presence of an asymmetric mode along with the symmetric mode. The extracted $Z_{\mathrm{peak}}$ values are influenced by the deformed shell gaps. GEF-predicted $Z_{\mathrm{peak}}$ values, $N_{\mathrm{peak}}$ values, and symmetric contributions are observed to agree with the experimental results.

The effect of the lepton's mass is significantly enhanced when the beam's energy is on the order of the lepton's mass. In the case of electrons, this corresponds to beam momenta on the order of a few $\text{MeV}/\text{c}$ and is negligible in higher energy experiments. In this paper, we calculate the differential cross section $d\sigma /d\mathrm{\Omega }$ for the helicity-flip meson exchange interference in elastic muon-proton $\left(\mu p\right)$ scattering ${\mu }^{-}p\to {\mu }^{-}p$. In particular, we examine the ${\pi }^0$ meson exchange in the $t$ channel for a longitudinally polarized beam and a transversely polarized target. We demonstrate the contribution to be larger for muons due to the lepton mass difference. Then we construct the corresponding beam-target double-spin asymmetries for the target polarized normal and parallel to the momentum transfer in the Breit frame, and then consider the model dependence of the calculation from the estimation of the ${\pi }^0\mu \mu$ vertex. The contribution was found to be on the order of $\approx 0.15\%$ for muons in the kinematic region of the Muon-Proton Scattering Experiment at the Paul-Scherrer Institute in Switzerland.

We study the real part of the static potential of a heavy quark-antiquark system in an anisotropic plasma medium. We use a quasiparticle approach where the collective dynamics of the plasma constituents is described using hard-loop perturbation theory. The parton distribution function is characterized by a set of parameters that can accurately describe the anisotropy of the plasma produced in a heavy ion collision. We calculate the potential numerically in strongly anisotropic systems and study the angular dependence of the distortion of the potential relative to the isotropic one. We obtain an analytic expression for the real part of the heavy quark potential in the limit of weak anisotropy using a model that expresses the potential in terms of effective screening masses that depend on the anisotropy parameters and the orientation of the quark-antiquark pair. A one-dimensional potential is formulated in terms of angle averaged screening masses that incorporate the anisotropy of the medium into a radial coordinate. We solve the corresponding Schrödinger equation and show that the magnitude of the binding energy typically increases with anisotropy. Anisotropy can play an important role, especially in states with nonzero angular momentum. This means that the number of bound states that are formed could depend on specific characteristics of the anisotropy of the plasma. Our study suggests that plasma anisotropy plays an important role in the dynamics of heavy quarkonium and motivates further study.

The ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction is critical for the understanding and interpretation of the late phases of stellar evolution as well as the ignition and nucleosynthesis in cataclysmic binary systems such as type Ia thermonuclear supernovas and x-ray superbursts. Direct measurement of this reaction has been performed at the University of Notre Dame using particle-$\gamma$ coincidence and differential thick-target techniques with SAND (a silicon detector array) at the high-intensity 5U Pelletron accelerator. Partial cross section results for the channels of $p_1$ to $p_{10}$ and ${\alpha }_1$ at center-of-mass energies of 2.65–5 MeV that are relevant to nuclear astrophysics are reported. The total $S^{*}\left(E\right)$ factor is constructed by taking into account contributions from the missing channels. The recommended reaction rate and its impact on the carbon burning process under astrophysical scenarios will be discussed.

High-precision lifetime measurements in ${}^{28}\mathrm{Mg}$ were performed to study neutron shell evolution in Mg isotopes and the onset of the $N=20$ island of inversion. Using both the recoil distance and Doppler shift attenuation methods, five lifetimes were measured in addition to six upper limits. The observation of two long-lived, negative-parity states demonstrate the importance of studying Mg isotopes for the contribution of intruder configurations to $sd$-shell nuclei. Lifetimes of the $2_1^{+}$ and $4_1^{+}$ states of 1.81(5) ps and $172{{(}_{-10}^{+11})}_{\mathrm{stat}.}{\left(4\right)}_{\mathrm{stop}.}{\left(8\right)}_{\mathrm{feed}.}{\left(4\right)}_{\mathrm{targ}.}\mathrm{fs}$, respectively, demonstrate a loss of collectivity with increasing spin in the yrast band, permitting for distinguishing between current theoretical models. These measurements also highlight the progression of yrast structure across the Mg isotopic chain from rotational at $N=12$ to large shape mixing at $N=16$ and back to collective behavior at $N=20$ but with dominating intruder configurations.

The changes in the mean-squared charge radius of ${}^{209}\mathrm{Tl}^g$ ($N=128$) and ${}^{207}\mathrm{Tl}^m$ ($N=126$) relative to ${}^{205}\mathrm{Tl}$ have been measured for the first time using the in-source laser resonance-ionization spectroscopy technique with the Laser Ion Source and Trap (LIST) at ISOLDE (CERN). The application of the LIST suppresses the dominant background from isobaric francium isotopes and allows access to thallium nuclides with $A⩾207$. The characteristic kink in the charge radii at the $N=126$ neutron shell closure, as well as the odd-even effect similar to that in the adjacent bismuth, lead, and mercury isotopic chains, have been observed. The self-consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. reproduces the behavior of charge radii in these isotopic chains near $N=126$. The comparison with calculations in the framework of the relativistic mean field (RMF) approach is also presented. In the case of the Fayans functional it is a specific form of pairing interaction with the dependence on the density gradient that is essential to provide agreement with the experimental charge radii. In particular, the kink is reproduced without the inversion of $g_{9/2}$ and $i_{11/2}$ neutron single-particle states, which is a prerequisite to correctly describe the kink in the RMF models.

A shell model effective interaction for nuclei beyond the double magic nucleus ${}^{78}\mathrm{Ni}$ is constructed. First, the single-particle evolutions for valence neutrons above the double magic ${}^{78}\mathrm{Ni}$ are systematically explored in the $N=51$ isotones using the large scale shell model (LSSM) calculations based on the constructed effective interaction. Subsequently, we calculate the excitation energies of $2_1^{+}$ states and reduced electric quadrupole transition probabilities $B(E2;2^{+}\to 0^{+})$ for $N=52$ isotones. Notably, our calculation gives the result most consistent with the trend of the $B\left(E2\right)$ values observed in the $N=52$ isotones, especially for ${}^{84}\mathrm{Ge}$, a result that poses a serious challenge to the theoretical model. Furthermore, the collectivity in $N=52$ isotones, as well as the roles of pseudo-SU(3) symmetry, are investigated via the calculated primary configurations of their ground states and the first excited states. Additionally, the low-lying structures and band characteristics of neutron-rich Ge and Se isotopes are investigated. The ground state and the $\gamma$-soft band are constructed in our LSSM calculations, aligning well with available experimental evidence. Finally, we present the calculated evolutions of low-lying states in neutron-rich Ge and Se isotopes. The predictions for the as-yet unobserved low-lying states in these nuclei provide a comprehensive dataset to guide and inform future experimental efforts to decipher the evolution of shell structures and collectivity.

We investigate the thermal production of charm quarks in the strongly interacting quark-gluon plasma (sQGP) created in heavy-ion collisions at relativistic energies. Our study is based on the off-shell parton-hadron-string dynamics (PHSD) transport approach describing the full time evolution of heavy-ion collisions on a microscopic basis with hadronic and partonic degrees of freedom. The sQGP is realized within the effective dynamical quasiparticle model (DQPM) which is adjusted to reproduce the lattice quantum chromodynamics (lQCD) results for the thermodynamic observables of the sQGP. Relying on the fact that the DQPM successfully describes the spatial diffusion coefficients $D_s$ from the lQCD, which control the interaction of charm quarks with thermal partons (expressed in terms of strongly interacting off-shell quasiparticles), we evaluate the production of charm quark pairs through the rotation of Feynman diagrams such that the incoming charm quark and outgoing light parton in elastic scattering diagrams are exchanged. The charm quark annihilation is realized by detailed balance. We find that the number of produced thermal charm quark pairs strongly depends on the charm quark mass in the QGP. While for the heavy charm quarks of mass $m_c=1.8\mathrm{GeV}$ it is subdominant compared to the primary charm production by binary nucleon-nucleon collisions at BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) energies, the numbers of primary and thermal charm quarks become comparable for a smaller (bare) $m_c=1.2\mathrm{GeV}$. Compared with the experimental data on the $R_{\mathrm{AA}}$ of $D$ mesons in heavy-ion collisions at RHIC and LHC energies, it is more favorable for charm quarks in the QGP to gain additional mass due to thermal effects rather than to have a low bare mass.