The electromagnetic dipole transitions in ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ and ${}^7\mathrm{Li}(n,\gamma ){}^8\mathrm{Li}$ reactions at the keV-energy region were analyzed simultaneously within the Skyrme Hartree-Fock potential model. The Skyrme Hartree-Fock calculation is adopted as a microscopic approach to obtain consistently the single-particle bound and scattering states in the calculation of the radial overlap function within the potential model. All nonresonant and resonant electromagnetic dipole transitions are taken into account. The electric dipole transitions are successfully described with the slightest adjustment. The resonant magnetic dipole transitions at 633 keV and 2184 keV of the ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ reaction, and the one at 222 keV of ${}^7\mathrm{Li}(n,\gamma ){}^8\mathrm{Li}$ are also analyzed. The astrophysical ${\mathcal{S}}_{17}\left(0\right)$ factor of the ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ reaction is found to be 22.3 eV b.

The production of neutron-rich transuranium nuclei with $Z=93–98$ in multinucleon transfer reactions induced by radioactive beams ${}^{92}\mathrm{Kr}, {}^{132}\mathrm{Sn}$, and ${}^{144}\mathrm{Xe}$ with actinide target ${}^{238}\mathrm{U}$ is investigated within the dinuclear system model with decay code gemini$++$. The isotopic distributions for reactions ${}^{136}\mathrm{Xe}+{}^{248}\mathrm{Cm}$ and ${}^{136}\mathrm{Xe}+{}^{249}\mathrm{Cf}$ are calculated and compared with the available experimental data. Theoretical calculations can reproduce the experimental results well. Both the $N/Z$ ratio equilibration mechanism and driving potential dominate the transfer process of nucleons. Reaction ${}^{132}\mathrm{Sn}+{}^{238}\mathrm{U}$ is an optimal projectile-target combination to obtain large production cross sections of neutron-rich isotopes with $Z=93–98$. The corresponding optimal incident energy is also explored. The production cross sections of 41 unknown neutron-rich transuranium isotopes with cross sections greater than 1 nb are predicted. The reaction ${}^{132}\mathrm{Sn}+{}^{238}\mathrm{U}$ at $E_{\mathrm{c}.\mathrm{m}.}=521.3$ MeV shows huge advantages in producing neutron-rich transuranium nuclei with $Z=93–98$.

A symplectic effective field theory that unveils the observed emergence of symplectic symmetry in atomic nuclei is advanced. Specifically, starting from a simple extension of the harmonic-oscillator Lagrangian, an effective field theory applied against symplectic basis states is shown to yield a Hamiltonian system with one fitted parameter. The scale of the system can be determined self-consistently as the ratio of the average volume of a nucleus assumed to be spherical to its volume as determined by the average number of oscillator quanta, which is stretched by the fact that the plane-wave solution satisfies the equations of motion at every order without the need for perturbative corrections. As an application of the theory, results for ${}^{20}\mathrm{Ne}$, ${}^{22}\mathrm{Ne}$, and ${}^{22}\mathrm{Mg}$ are presented that yield energy spectra, $B\left(E2\right)$ values, and matter radii in good agreement with experimentally measured results.

The search for a first-order phase transition in strongly interacting matter is one of the major objectives in the exploration of the phase diagram of quantum chromodynamics (QCD). In the present work we investigate dilepton radiation from the hot and dense fireballs created in Au-Au collisions at projectile energies of 1–2 $A\mathrm{GeV}$ for potential signatures of a first-order transition. Toward this end, we employ a hydrodynamic simulation with two different equations of state, with and without a phase transition. The latter is constrained by susceptibilities at vanishing chemical potential from lattice-QCD as well as neutron star properties, while the former is implemented via modification of the mean fields in the quark phase. We find that the latent heat involved in the first-order transition leads to a substantial increase in the low-mass thermal emission signal by about a factor of two above the crossover scenario.

Background: The $\alpha$-nucleus optical potential plays a crucial role in the calculation of $\alpha$-induced reaction cross sections at low energies in the statistical model which are the basis for the reliable prediction of astrophysical reaction rates.

Purpose: The present study attempts to constrain the $\alpha$-nucleus potential for ${}^{144}\mathrm{Sm}$ $+$ $\alpha$ by the analysis of angular distributions of ${}^{144}\mathrm{Sm}(\alpha ,\alpha ){}^{144}\mathrm{Sm}$ elastic scattering.

Methods: Between ${20}^{\circ }$ and ${175}^{\circ }$ complete elastic $\alpha$ scattering angular distributions were measured on the ${}^{144}\mathrm{Sm}$ $p$ isotope with high precision at $E_{\mathrm{lab}}$ = 16.13 MeV, at $E_{\mathrm{lab}}$ = 18.07 MeV, and at $E_{\mathrm{lab}}$ = 19.87 MeV.

Results: The angular distributions at 18 and at 20 MeV allow a determination of the parameters of the $\alpha$-nucleus potential with small uncertainties, whereas the 16 MeV data cannot constrain well these parameters. A prediction of the ${}^{144}\mathrm{Sm}(\alpha ,\gamma ){}^{148}\mathrm{Gd}$ cross section at very low energies from the present fits overestimates the experimental data from literature.

Conclusions: The tension between the relatively high cross sections from the analysis of elastic ($\alpha ,\alpha$) scattering at $16–20$ MeV and the low cross sections of the ($\alpha ,\gamma$) data at deep sub-Coulomb energies around 10 MeV requires further study. The energy gap between the ($\alpha ,\alpha$) and ($\alpha ,\gamma$) data can be best filled by new ($\alpha ,n$) data.

Background: Shape deformations and charge radii, basic properties of atomic nuclei, are influenced by both the global features of the nuclear force and the nucleonic shell structure. As functions of proton and neutron number, both quantities show regular patterns and, for nuclei away from magic numbers, they change very smoothly from nucleus to nucleus.

Purpose: In this paper, we explain how the local shell effects are impacting the statistical correlations between quadrupole deformations and charge radii in well-deformed even-even Er, Yb, and Hf isotopes. This implies, in turn, that sudden changes in correlations can be useful indicators of underlying shell effects.

Methods: Our theoretical analysis is performed in the framework of self-consistent mean-field theory using quantified energy density functionals and density-dependent pairing forces. The statistical analysis is carried out by means of the linear least-square regression.

Results: The local variations of nuclear quadrupole deformations and charge radii, explained in terms of occupations individual deformed Hartree-Fock orbits, make and imprint on statistical correlations of computed observables. While the calculated deformations or charge radii are, in some cases, correlated with those of their even-even neighbors, the correlations seem to deteriorate rapidly with particle number.

Conclusions: The statistical correlations between nuclear deformations and charge radii of different nuclei are affected by the underlying shell structure. Even for well deformed and superfluid nuclei for which these observables change smoothly, the correlation range is rather short. This result suggests that the frequently made assumption of reduced statistical errors for the differences between smoothly-varying observables cannot be generally justified.

Within a transport model, we study the neutron-proton differential transverse flow and its excitation function in central ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions at 270 MeV/nucleon. To more accurately evaluate effects of the high-density behavior of symmetry energy $E_{\mathrm{sym}}\left(\rho \right)$ on this observable, we also consider the uncertainties of $E_{\mathrm{sym}}\left(\rho \right)$ around the saturation density ${\rho }_0$. It is shown that the neutron-proton differential transverse flow and its excitation function are mainly sensitive to the slope $L$ of $E_{\mathrm{sym}}\left(\rho \right)$ at ${\rho }_0$. However, the effects of low-density behavior of $E_{\mathrm{sym}}\left(\rho \right)$ on this observable should also be considered. Therefore, it is suggested that measurements of the neutron-proton differential transverse flow and its excitation function may provide useful complements to the constraints on $L$ extracted from the spectral pion ratio in $\mathrm{S}\pi \mathrm{RIT}$ experiments.

We study the interaction of leading jet partons in a strongly interacting quark-gluon plasma (sQGP) medium based on the effective dynamical quasiparticle model (DQPM). The DQPM describes the nonperturbative nature of the sQGP at finite temperature $T$ and baryon chemical potential ${\mu }_B$ based on a propagator representation of massive off-shell partons (quarks and gluons) whose properties (characterized by spectral functions with $T$- and ${\mu }_B$-dependent masses and widths) are adjusted to reproduce the lQCD EoS for the QGP in thermodynamic equilibrium. We present the results for the jet transport coefficients, i.e., the transverse momentum transfer squared per unit length $\widehat{q}$ as well as the energy loss per unit length $\mathrm{\Delta }E=dE/dx$, in the QGP and investigate their dependence on the temperature $T$ and baryon chemical potential ${\mu }_B$ as well as on jet properties such as the leading jet parton momentum, mass, flavor, and the choice of the strong coupling constant. In this first study only elastic scattering processes of a leading jet parton with the sQGP partons are explored discarding presently the radiative processes (such as gluon Bremsstrahlung). We present a comparison of our results for the elastic energy loss in the sQGP medium with the pQCD results obtained by the BAMPS and LBT models as well as with other theoretical approaches such as lattice QCD and the LO-HTL and also with estimates of $\widehat{q}/T^3$ by the color string percolation model (CSPM) and the JET and JETSCAPE Collaborations based on a comparison of hydrodynamical calculations with experimental heavy-ion data.

Under the framework of vector meson dominance model, the value of scattering length can be expressed as a function of the ratio between total cross section $\sigma \left(W\right)$ and $R\left(W\right)$, where $R\left(W\right)$ is the ratio between final momentum $|{\mathbf{p}}_3|$ and initial momentum $|{\mathbf{p}}_1|$ and positively correlated with the center-of-mass energy. Based on the theoretical study of charmonium's photoproduction within two gluon exchange model and effective Pomeron model, we research the scattering lengths of vector mesons and proton interaction in this work. Results show that the scattering length $|{\alpha }_{J/\psi p}|$ obtained from the two models are close and basically in agreement with the theoretical prediction of Strakovsky and co-workers. Additionally, we first calculate the scattering length of the $\psi \left(2S\right)$-proton interaction in the two gluon exchange model and effective Pomeron model as $1.31\pm 0.92$ am (1 am = ${10}^{-3}$ fm) and $3.24\pm 0.63$ am, respectively. This is a little bit different from the two models and requires precise measurements from subsequent experiments. In short, our results will provide a theoretical reference for future studies on characterizing the vector meson-proton scattering length.

Ground-state properties of finite drops of $\alpha$ particles (Q-balls) are studied within a field-theoretical approach in the mean-field approximation. The strong interaction of $\alpha$'s is described by the scalar field with a sextic Skyrme-like potential. The radial profiles of scalar and Coulomb fields are found by solving the coupled system of Klein-Gordon and Poisson equations. The formation of shell-like nuclei, with vanishing density around the center, is predicted at high enough attractive strength of Skyrme potential. The equilibrium values of energy and baryon number of Q-balls and Q-shells are calculated for different sets of interaction parameters. Empirical binding energies of $\alpha$-conjugate nuclei are reproduced only if the gradient term in the Lagrangian is strongly enhanced. It is demonstrated that this enhancement can be explained by a finite size of $\alpha$ particles.

Background: Nuclear spectroscopy of neutron-rich isotopes provides important information on their nuclear structure and has a valuable impact on the modeling of the $r$-process path. Particularly interesting are nuclei close to doubly-magic species, e.g., ${}^{132}\mathrm{Sn}$, with only several valence particles. Such is the barely explored ${}^{137}\mathrm{I}$ nucleus, investigated here in detail.

Purpose: To establish excited states in ${}^{137}\mathrm{I}$, $\beta$ decay of the ${}^{137}\mathrm{Te}$ ground state is studied. In addition, the unknown $\beta$-delayed neutron-emission channel of ${}^{137}\mathrm{Te}$ to ${}^{136}\mathrm{I}$ is inspected. Search for levels and for candidates for Gamow-Teller and first-forbidden transitions between the mother nucleus and excited states in the daughter nucleus is conducted within the experimental observations.

Methods: $\beta$-delayed $\gamma$-ray spectroscopy is employed to study excited states in ${}^{137}\mathrm{I}$. The nucleus is populated in the decay of a mass-separated beam of ${}^{137}\mathrm{Te}$, produced in neutron-induced fission of ${}^{235}\mathrm{U}$.

Results: The new level scheme of ${}^{137}\mathrm{I}$ populated in $\beta$ decay is established. The half-life $T_{1/2}$ of ${}^{137}\mathrm{Te}$ is determined to be 2.46(5) s. The $\beta$-delayed neutron-emission probability $P_n$ value of ${}^{137}\mathrm{Te}$ is deduced as a lower limit to be 2.63(85)%.

Conclusions: The experimental results are an important input to the theoretical description of nuclei in the region, being well interpreted within large-scale shell model calculations, and provide essential information on the first-forbidden transitions beyond $N=82$ and $Z=50$.

The $E1$ and $M1$ contributions to ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ at low energies are calculated in halo effective field theory. The excited ${}^7\mathrm{Be}^{★}$ core is included as an explicit degree of freedom in a coupled-channels calculation. The $E1$ transition is calculated up to next-to-next-to-leading order. The leading contribution from $M1$ transition that gives significant contribution in a narrow energy region around the $1^{+}$ resonance state of ${}^8\mathrm{B}$ is included. We compare our results with previous halo effective field theory calculations that also included the ${}^7\mathrm{Be}^{★}$ as an explicit degree of freedom. We disagree with these previous calculations in both the formal expressions and also in the analysis. Bayesian inference of the data gives $S_{17}\left(0\right)=21.0\left(7\right)$ eV b when combined with the expected theory error.

The decay of excited states in ${}^{255}\mathrm{No}$ was investigated by applying the evaporation-residue–conversion-electron correlation technique. Two new isomeric states were observed in ${}^{255}\mathrm{No}$ together with the previously known one. Excitation energies of the isomeric states were estimated based on the energies of conversion electrons and $\gamma$ rays from correlation chains. These results were in accord with theoretical calculations based on the mean-field models. A tentative decay scheme of isomeric states in ${}^{255}\mathrm{No}$ is proposed, and their Nilsson configurations are discussed. The energy decrease of the $11/2^{-}$[725] Nilsson level for heavy $N=153$ isotones as a function of increasing proton number is confirmed.

Background: Two-nucleon transfer reactions provide a unique tool to understand the correlation between nucleon pairs. Two-nucleon $(pp,$ $nn$, and $np)$ transfer reactions can occur via isoscalar $(T=0,$ $S=1)$ or isovector $(T=1,$ $S=0)$ processes. In particular, the isoscalar pair transfer can be induced by the $(\alpha ,d)$ or $({}^6\mathrm{Li},\alpha )$ probes. In the past, most of the isoscalar $np$-transfer studies were performed with the $(\alpha ,d)$ reaction, but this probe is strongly momentum mismatched with respect to other two-nucleon transfer reactions.

Purpose: We aim to investigate the interplay between direct and sequential reaction mechanisms from the analysis of experimental $({}^6\mathrm{Li},\alpha )$ angular distributions in light targets.

Method: Differential cross sections of $({}^6\mathrm{Li},\alpha )$ reactions at a beam energy of 20 MeV were measured with ${}^{12}\mathrm{C}$ and ${}^{19}\mathrm{F}$ targets. The interplay between direct and sequential transfer mechanisms in the experimental angular distributions was investigated with coupled-reaction-channels calculations.

Results: The experimental angular distributions of isoscalar $np$ transfer were compared with theoretical calculations assuming a direct or a sequential reaction mechanism. Direct $np$-transfer calculations describe successfully most of the angular distributions. The sequential transfer mechanism is about two orders of magnitude smaller than the direct process.

Conclusions: The present results suggest a significant $np$ correlation in the ${}^{12}\mathrm{C}({}^6\mathrm{Li},\alpha ){}^{14}\mathrm{N}^{*}$ and ${}^{19}\mathrm{F}({}^6\mathrm{Li},\alpha ){}^{21}\mathrm{Ne}^{*}$ reactions. Despite the relatively low cross section for the reactions with the asymmetric ${}^{19}\mathrm{F}$ target, the direct transfer mechanism remains dominant over the sequential process. Further studies including measurements with other asymmetric $sd$-shell nuclei will be required to fully understand the isoscalar and isovector $np$-transfer mechanism in this nuclear region.

We demonstrate high prediction accuracy of three important properties that determine the initial geometry of the heavy-ion collision (HIC) experiments by using supervised machine learning (ML) methods. These properties are the impact parameter, the eccentricity, and the participant eccentricity. Although ML techniques have been used previously to determine the impact parameter of these collisions, we study multiple ML algorithms, their error spectrum, and sampling methods using exhaustive parameter scans and ablation studies to determine a combination of efficient algorithm and tuned training set that gives multifold improvement in accuracy for all three different heavy-ion collision models. The three models chosen are a transport model, a hydrodynamic model, and a hybrid model. The motivation of using three different heavy-ion collision models was to show that even if the model is trained using a transport model, it gives accurate results for a hydrodynamic model as well as a hybrid model. We show that the accuracy of the impact-parameter prediction depends on the centrality of the collision. With the standard application of ML training methods, prediction accuracy is considerably low for central collisions. Our method increases this accuracy by multiple folds. We also show that the eccentricity prediction accuracy can be improved by inclusion of the impact parameter as a feature in all these algorithms. We discuss how the errors can be minimized and the accuracy can be improved to a great extent in all the ranges of impact-parameter and eccentricity predictions.

While experimental observations, such as the mass hierarchy effect, are attributed and analyzed within radiative models, their interpretation crucially depends on collisional energy loss contribution, which is often neglected in such analyses. To our knowledge, there are neither an established (direct) simple relation between collisional energy loss and heavy quark mass nor an observable that quantifies this effect. On the other hand, the upcoming high-luminosity measurements at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) will generate heavy flavor data with unprecedented precision, providing an opportunity to utilize high-$p_{\perp }$ heavy flavor data to analyze the interaction mechanisms in the quark-gluon plasma. To this end, we employ a recently developed dreena framework based on our dynamical energy loss formalism to study the mass hierarchy in heavy flavor suppression. We present (i) an analytical derivation of a direct relation between collisional suppression/energy loss and heavy quark mass; (ii) a novel observable sensitive only to the collisional energy loss mechanism to be tested by future high-precision experiments, and (iii) analytical and numerical extraction of the mass hierarchy in collisional energy losses through this observable.

A precise determination of the atomic mass of ${}^{75}\mathrm{As}$ has been performed utilizing the double Penning trap mass spectrometer, JYFLTRAP. The mass excess is measured to be $-73035.519\left(42\right)\mathrm{keV}/c^2$, which is a factor of 21 more precise and $1.3\left(9\right)\mathrm{keV}/c^2$ lower than the adopted value in the newest Atomic Mass Evaluation (AME2020). This value has been used to determine the ground-state–to–ground-state electron-capture decay $Q$ value of ${}^{75}\mathrm{Se}$ and ${\beta }^{-}$ decay $Q$ value of ${}^{75}\mathrm{Ge}$, which are derived to be 866.041(81) keV and 1178.561(65) keV, respectively. Using the nuclear energy-level data of 860.00(40) keV, 865.40(50) keV (final states of electron capture), and 1172.00(60) keV (final state of ${\beta }^{-}$ decay) for the excited states of ${}^{75}\mathrm{As}^{*}$, we have determined the ground-state–to–excited-state $Q$ values for two transitions of ${}^{75}\mathrm{Se}\to {}^{75}\mathrm{As}^{*}$ and one transition of ${}^{75}\mathrm{Ge}\to {}^{75}\mathrm{As}^{*}$. The ground-state–to–excited-state $Q$ values are determined to be 6.04(41) keV, 0.64(51) keV, and 6.56(60) keV, respectively, thus confirming that the three low $Q$-value transitions are all energetically valid and one of them is a possible candidate channel for antineutrino mass determination. Furthermore, the ground-state–to–excited-state $Q$ value of transition ${}^{75}\mathrm{Se}\to {}^{75}\mathrm{As}^{*}$ [865.40(50) keV] is revealed to be ultralow ($<1$ keV) and the first-ever confirmed electron capture transition possessing an ultralow $Q$ value from direct measurements.

The mutual correlation between the nuclear equation of state (EOS) and the bulk properties of neutron stars (NS) is crucial in probing both of them. Here, we use EOSs of hot $npe$ ($npe\mu$) nuclear matter, based on the density-dependent CDM3Y-Paris nucleon-nucleon interaction in the nonrelativistic Hartree-Fock scheme, to investigate the temperature dependence of the core-crust transition properties under $\beta$ equilibrium, at the inner edge of NS. We use four EOSs that provide symmetric nuclear matter saturation incompressibility of 218 and 252 MeV, with two parametrizations of the density dependence of the isovector part of the M3Y force. We found that the softer EOS estimates larger proton fraction in the NS matter and indicates a wider range for direct Urca (DU) cooling process within the core center of NSs. Increasing the temperature decreases the density corresponding to the threshold proton fraction for DU process, increasing the region for the DU process inside NSs. The muons decrease the isospin asymmetry of the $npe\mu$ NS matter at its core center, its thermal pressure, and the DU threshold density. The muon fraction slightly changes with temperature. A value of about half the proton fraction is inferred for the $\beta$-stable muon fraction of hot $npe\mu$ matter, around the core center. Based on the four considered EOSs, the liquid core-solid crust transition density, pressure, and proton fraction are estimated to increase from $(0.54\pm 0.02){\rho }_0, 0.36\pm 0.12\mathrm{MeV}{\mathrm{fm}}^{-3}$, and 0.03, respectively at $T=0\mathrm{MeV}$, to $(0.85\pm 0.04){\rho }_0, 7.36\pm 0.52\mathrm{MeV}{\mathrm{fm}}^{-3}$, and 0.14, respectively at $T=50\mathrm{MeV}$.

The ${}^{16}\mathrm{F}$ nucleus is situated at the proton drip line and is unbound by proton emission by only about 500 keV. Continuum coupling is then prominent in this nucleus. Added to that, its low-lying spectrum consists of narrow proton resonances as well. It is therefore a very good candidate to study nuclear structure and reactions at the proton drip line. The low-lying spectrum and scattering proton-proton cross section of ${}^{16}\mathrm{F}$ were calculated with the coupled-channels Gamow shell model framework in this case using an effective Hamiltonian. Experimental data are very well reproduced, as were those of its mirror nucleus ${}^{16}\mathrm{N}$. Isospin-symmetry breaking generated by the Coulomb interaction and continuum coupling explicitly appears in our calculations. In particular, the different continuum couplings in ${}^{16}\mathrm{F}$ and ${}^{16}\mathrm{N}$ involving $s_{1/2}$ partial waves allow one to explain the different ordering of low-lying states in their spectra.

We report a high-precision mass measurement of ${}^{24}\mathrm{Si}$, performed with the Low Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory. The atomic mass excess, $10753.8$(37) keV, is a factor of 5 more precise than previous results. This substantially reduces the uncertainty of the ${}^{23}\mathrm{Al}(p,\gamma ){}^{24}\mathrm{Si}$ reaction rate, which is a key part of the rapid proton capture ($rp$) process powering type I x-ray bursts. The updated rate constrains the onset temperature of the $(\alpha ,p)$ process at the ${}^{22}\mathrm{Mg}$ waiting point to a precision of 9%.