The performance of nuclear reactors and other nuclear systems depends on a precise understanding of the neutron interaction cross sections for materials used in these systems. These cross sections exhibit resonant structure whose shape is determined in part by the angular-momentum quantum numbers of the resonances. The correct assignment of the quantum numbers of neutron resonances is, therefore, paramount. In this project, we apply machine learning to automate the quantum number assignments using only the resonances' energies and widths and not relying on detailed transmission or capture measurements. The classifier used for quantum number assignment is trained using stochastically generated resonance sequences whose distributions mimic those of real data. We explore the use of several physics-motivated features for training our classifier. These features amount to out-of-distribution tests of a given resonance's widths and resonance-pair spacings. We pay special attention to situations where either capture widths cannot be trusted for classification purposes or where there is insufficient information to classify resonances by the total spin $J$. We demonstrate the efficacy of our classification approach using simulated and actual ${}^{52}\mathrm{Cr}$ resonance data.

Background: The reliability of a previous $\alpha$-particle optical-model potential (OMP) on nuclei with mass number $45\le A\le 209$ was proved for emitted $\alpha$ particles as well, for proton-induced reactions on Zn isotopes [Phys. Rev. C 91, 064611 (2015), Paper I]. However, the same was not the case of neutrons on Zr stable isotopes [Phys. Rev. C 96, 044610 (2017), Paper II].

Purpose: A recent assessment of this potential also for nucleon-induced $\alpha$ emission on $A\approx 60$ nuclei, including pickup direct reaction and eventual giant quadrupole resonance (GQR) $\alpha$ emission, was completed for neutrons incident on Zr, Nb, and Mo stable isotopes.

Methods: Consistent sets of input parameters, determined through analysis of independent data, are involved while no further empirical rescaling factors of the $\gamma$ and nucleon widths have been involved.

Results: A suitable account of all competitive reaction channels is confirmed by careful uncertainty analysis, to avoid parameter ambiguities and/or error compensation. Additional validation of this potential is also supported by recently measured $(\alpha ,\gamma )$ and $(\alpha ,n)$ cross sections of Zr and Mo nuclei.

Conclusions: An increase of the $\alpha$ emission beyond the statistical predictions, through consideration of additional reaction channels of the pickup direct interaction and GQR-like decay, makes possible the description of both absorption and emission of $\alpha$ particles by the same optical potential.

The early dynamics in heavy-ion collisions involves a rapid, far from equilibrium evolution. This early pre-equilibrium stage of the dynamics can be modeled using kinetic equations. The effect of this pre-equilibrium stage on final observables derived from transverse momenta of emitted particles is small. The kinetic equations in the relaxation time approximation for a nonboost invariant system are solved. The asymmetry of the flow with respect to the reaction plane at different rapidities is found to be very sensitive to the degree of nonequilibrium in the evolution. This suggests that the rapidity odd directed flow could be studied to identify the occurrence of nonequilibrium effects and to estimate the asymmetry of the pressure between the longitudinal and transverse directions in the collision.

We address the question of the role of low-energy nuclear physics data in constraining neutron star global properties, e.g., masses, radii, angular momentum, and tidal deformability, in the absence of a phase transition in dense matter. To do so, we assess the capacity of 415 relativistic mean field and nonrelativistic Skyrme-type interactions to reproduce the ground state binding energies, the charge radii, and the giant monopole resonances of a set of spherical nuclei. The interactions are classified according to their ability to describe these characteristics, and we show that a tight correlation between the symmetry energy and its slope is obtained provided that $N=Z$ and $N\ne Z$ nuclei are described with the same accuracy (mainly driven by the charge radius data). By additionally imposing the constraints from isobaric analog states and neutron skin radius in ${}^{208}\mathrm{Pb}$, we obtain the following estimates: $E_{\mathrm{sym},2}=31.8\pm 0.7$ MeV and $L_{\mathrm{sym},2}=58.1\pm 9.0$ MeV. We then analyze predictions of neutron star properties and we find that the $1.4M_{\odot }$ neutron star (NS) radius lies between 12 and 14 km for the “better” nuclear interactions. We show that (i) the better reproduction of low-energy nuclear physics data by the nuclear models only weakly impacts the global properties of canonical mass neutron stars and (ii) the experimental constraint on the symmetry energy is the most effective one for reducing the uncertainties in NS matter. However, since the density region where constraints are required are well above densities in finite nuclei, the largest uncertainty originates from the density dependence of the energy density functional (EDF), which remains largely unknown.

The star-to-star anticorrelation of sodium and oxygen is a defining feature of globular clusters, but, to date, the astrophysical site responsible for this unique chemical signature remains unknown. Sodium enrichment within these clusters depends sensitively on reaction rate of the sodium destroying reactions ${}^{23}\mathrm{Na}(p,\gamma )$ and ${}^{23}\mathrm{Na}(p,\alpha )$. In this paper, we report the results of a ${}^{23}\mathrm{Na}{({}^3\mathrm{He},d)}^{24}\mathrm{Mg}$ transfer reaction carried out at Triangle Universities Nuclear Laboratory using a $21\mathrm{MeV}{}^3\mathrm{He}$ beam. Astrophysically relevant states in ${}^{24}\mathrm{Mg}$ between $11<E_x<12\mathrm{MeV}$ were studied using high-resolution magnetic spectroscopy, thereby allowing the extraction of excitation energies and spectroscopic factors. Bayesian methods are combined with the distorted wave Born approximation to assign statistically meaningful uncertainties to the extracted spectroscopic factors. For the first time, these uncertainties are propagated through to the estimation of proton partial widths. Our experimental data are used to calculate the reaction rate. The impact of the new rates are investigated using asymptotic giant branch star models. It is found that while the astrophysical conditions still dominate the total uncertainty, intramodel variations on sodium production from the ${}^{23}\mathrm{Na}(p,\gamma )$ and ${}^{23}\mathrm{Na}(p,\alpha )$ reaction channels are a lingering source of uncertainty.

We report on high-resolution laser spectroscopy studies on ${}^{249\text{–}253}\mathrm{Cf}$ with spectral linewidths in the order of 100 MHz carried out at the RISIKO mass separator at Mainz University. In total three atomic ground-state transitions were investigated and the hyperfine parameters for the odd-$A$ isotopes and isotope shift for all examined isotopes have been determined from the measured spectra. The isotope shift measurements allowed tracking of changes in mean-squared charge radii across the deformed nuclear shell closure at $N=152$, whereby shape discontinuities were not observed. Experimental hyperfine coupling constants of the atomic ground state were combined with relativistic many-body atomic calculations to extract the nuclear magnetic-dipole moment of ${}^{249}\mathrm{Cf}$ with improved precision to ${\mu }_I{(}^{249}\mathrm{Cf})=-0.395\left(17\right){\mu }_N$, whereas ${\mu }_I{(}^{251}\mathrm{Cf})=-0.571\left(24\right){\mu }_N$ and ${\mu }_I{(}^{253}\mathrm{Cf})=-0.731\left(35\right){\mu }_N$ were derived for the first time. Additionally, the spectroscopic quadrupole moments $Q_{\mathrm{S}}{(}^{249}\mathrm{Cf})=6.27\left(33\right)e\mathrm{b}$ and $Q_{\mathrm{S}}{(}^{253}\mathrm{Cf})=5.53\left(51\right)e\mathrm{b}$ were extracted.

In this paper, we considered the cluster radioactivity half-lives for all known cluster decay modes (i.e., from ${}^{14}\mathrm{C}$ up to ${}^{34}\mathrm{Si}$) that these nuclei were first satisfied by the observed systematics [Silisteanu and Scheid, Phys. Rev. C 51, 2023 (1995), Poenaru et al., Phys. Rev. C 83, 014601 (2011); Ni et al., Phys. Rev. C 78, 044310 (2008)]. The Coulomb and proximity potential model for deformed nuclei is considered as penetration of the emitter particle through the potential barrier formed by the nuclear, Coulomb, and centrifugal interactions between the emitter particle and nucleus. The spins and parities of the parent and daughter nuclei in addition to the quadrupole $\left({\beta }_2\right)$ and hexadecapole $\left({\beta }_4\right)$ deformations of the parent nuclei are taken into account for the calculation of the cluster radioactivity half-lives. Our results exhibit, which the minimum $\mathrm{lo}{\mathrm{g}}_{10}{T}_{1/2}$ value denotes doubly magic ${}^{208}\mathrm{Pb}$ ($Z=82$, $N=126$) as the daughter nuclei.

When searching for anomalous chiral effects in heavy-ion collisions, one of the most crucial points is the relationship between the signal and the background. In this Letter, we present a simulation in a modified blast wave model at CERN Large Hadron Collider energy, which can simultaneously characterize the majority of measurable quantities, in particular, the chiral magnetic effect (CME) and the chiral magnetic wave (CMW) observables. Such a universal description, naturally and quantitatively unifies the CME and the CMW studies and brings to light the connection with the local charge conservation (LCC) background. Moreover, a simple phenomenological approach is performed to introduce the signals, aiming at quantifying the maximum allowable strength of the signals within experimental precision. Such a constraint provides a novel perspective to understand the experimental data and sheds new light on the study of anomalous chiral effects as well as charge dependent correlations.

Background: Inelastic $\alpha$-particle scattering at energies of a few hundred MeV and very-forward scattering angles including 0° has been established as a tool for the study of the isoscalar giant monopole (IS0) strength distributions in nuclei. This compressional mode of nuclear excitation can be used to derive the incompressibility of nuclear matter.

Purpose: An independent investigation of the IS0 strength in nuclei across a wide mass range was performed using the $0^{\circ }$ facility at iThemba Laboratory for Accelerator Based Sciences (iThemba LABS), South Africa, to understand differences observed between IS0 strength distributions in previous experiments performed at the Texas A&M University (TAMU) Cyclotron Institute, USA and the Research Center for Nuclear Physics (RCNP), Japan.

Methods: The isoscalar giant monopole resonance (ISGMR) was excited in ${}^{58}\mathrm{Ni}, {}^{90}\mathrm{Zr}, {}^{120}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ using $\alpha$-particle inelastic scattering with a 196 MeV $\alpha$ beam and scattering angles ${\theta }_{\text{Lab}}=0^{\circ }$ and $4^{\circ }$. The K600 magnetic spectrometer at iThemba LABS was used to detect and momentum analyze the inelastically scattered $\alpha$ particles. The IS0 strength distributions in the nuclei studied were deduced with the difference-of-spectra (DoS) technique including a correction factor for the $4^{\circ }$ data based on the decomposition of $L>0$ cross sections in previous experiments.

Results: IS0 strength distributions for ${}^{58}\mathrm{Ni}, {}^{90}\mathrm{Zr}, {}^{120}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ are extracted in the excitation-energy region $E_{\mathrm{x}}=9–25$ MeV. Using correction factors extracted from the RCNP experiments, there is a fair agreement with their published IS0 results. Good agreement for IS0 strength in ${}^{58}\mathrm{Ni}$ is also obtained with correction factors deduced from the TAMU results, while marked differences are found for ${}^{90}\mathrm{Zr}$ and ${}^{208}\mathrm{Pb}$.

Conclusions: Previous measurements show significant differences in the IS0 strength distributions of ${}^{90}\mathrm{Zr}$ and ${}^{208}\mathrm{Pb}$. This work demonstrates clear structural differences in the energy region of the main resonance peaks with possible impact on the determination of the nuclear matter incompressibility presently based on the IS0 centroid energies of these two nuclei. The results also suggest that, for an improved determination of the incompressibility, theoretical approaches should aim at a description of the full strength distributions rather than the centroid energy only.

Multidimensional potential energy surfaces (PES) are calculated using the microscopic-macroscopic approach. The nuclear shapes are described by Cassinian ovals generalized by the inclusion of ${\alpha }_1$, ${\alpha }_3$, and ${\alpha }_4$ shape parameters in addition to the main fission coordinate $\alpha$. The influence of the octupole deformation $\left({\alpha }_3\right)$ on the PES is studied in the case of the nuclear fission of ${}^{236}\mathrm{U}$. It is found that ${\alpha }_3$ plays an important role in the last stage of the fission process; for instance, it lowers the third minimum and the third barrier. Two methods to calculate the static fission path are investigated. They are found to be consistent in the sense that they lead to the same fission barrier. In certain subspaces, the least energy paths from the ground state to scission present discontinuities around one of the saddles. They are caused by sharp changes in the nuclear shapes involved occurring without a change in energy. Such transitions are smoothed out by the principle of stationary action, which transforms a discontinuous path into a continuous one. Finally, various macroscopic models have been employed in order to study their influence on the energies and positions of the saddles and the minima.

Heavy-ion reaction studies in the incident energy regime $\le$ 20 MeV/nucleon have suggested multiple signatures of preequilibrium emission during the compound nucleus formation phenomenon and the presence of incomplete fusion, both of which vary with the incident energy and projectile-target combination. However, the available reaction data are insufficient to accurately decipher these contributions as the reports have a finite dependency on the predictions from theoretical models. Therefore, sound data interpretation with robust nuclear models is fundamental to unfolding the underlying processes. We report a new study of excitation functions of residues produced from the ${}^{12}\mathrm{C}+\mathrm{Zr}$ reactions up to 6.3 MeV/nucleon energy. Cross sections of 16 evaporation residues were measured through off-beam $\gamma$-ray spectroscopy. Excitation functions of the evaporation residues are reported at 14 energy points and compared with the reaction model code empire-3.2.2, with variations in nuclear level density. Additionally, the overall contribution of precompound and compound nuclear processes is discussed quantitatively within the realms of empire-3.2.2 model code.

The effects of the Pauli exclusion principle are investigated regarding the calculations of the nuclear cluster radioactivity using the double-folding formalism. To this purpose, the variation in the internal kinetic energy is considered at the overlapping regions between the densities of the two interacting nuclei as a modification term by employing the extended Thomas-Fermi approach. The effects of the Pauli exclusion principle on the internal energy of the dinuclear system and the standard deviation of the calculated half-lives from their corresponding experimental data are discussed. The results reveal that considering such corrections in calculating the double-folding potential leads to lower standard deviations, which are more consistent with experimental data than other semiempirical formulas.

We present a generalized effective string rope model (GESRM), which aims to describe the initial stage of relativistic heavy ion collisions and to give us an initial state for further hydrodynamical calculations. We start with the effective string rope model (ESRM) [V. K. Magas, L. P. Csernai, and D. D. Strottman, Phys. Rev. C 64, 014901 (2001); Nucl. Phys. A 712, 167 (2002)] and generalize it in order to take into account fluctuations in the initial state following the Glauber Monte Carlo approach. Results from symmetric nucleus-nucleus collisions at different impact parameters are presented at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC); additionally we study asymmetric $A+\mathrm{Au}$ head-on collisions. We also compare the results obtained in the GESRM on an event-by-event basis with those received averaging initial states over many events.

Nucleon resonance contributions to the polarized proton $g_1$ and $g_2$ structure functions are computed from resonance electroexcitation amplitudes extracted from CLAS exclusive meson electroproduction data. Including resonances in the mass range up to 1.75 GeV, and taking into account the interference between excited states, we compare the resonant contributions with the polarized proton structure function and polarization asymmetry data from Jefferson Lab 6 GeV measurements. All resonance-like structure observed in the polarized structure functions and asymmetries can be attributed to the resonant contributions, confirming their essential role in the behavior of $g_1$ and $g_2$ in the resonant region over the entire range $Q^2<7.5{\mathrm{GeV}}^2$ covered by the measurements. Comparing the resonance contributions with the $g_1$ and $g_2$ structure functions computed from parton distribution functions extrapolated from the deep-inelastic region, we also quantify the degree to which quark-hadron duality holds for $g_1$ and $g_2$ and their moments.

Background: For understanding the synthesis of elements in the universe, precise knowledge of reaction rates and cross sections is paramount. This is especially true for the $p$ process because its study requires large network calculations including thousands of nuclei and nuclear reactions with little room for simplification. Therefore, robust theoretical methods for predicting cross sections are needed which are usually based on Hauser-Feshbach calculations. These calculations use physics input in the form of $\gamma$-ray strength functions, nuclear level densities, and particle $+$ nucleus optical-model potentials. These have to be constrained using experimental results.

Purpose: To constrain the $\alpha$ optical-model potential $\alpha$-induced reactions are well suited. The ytterbium isotopic chain not only offers multiple stable isotopes on which cross sections can be measured and insights into the evolution of the $\alpha$ optical-model potential with the neutron-to-proton ratio can be gained but also includes the $p$ nucleus ${}^{168}\mathrm{Yb}$. Its abundance is significantly impacted by the ${}^{164,166}\mathrm{Yb}(\alpha ,\gamma )$ reactions and is, therefore, also affected by the constraints resulting from the experiment presented in this paper.

Method: To study the ${}^{170,172}\mathrm{Yb}(\alpha ,n){}^{173,175}\mathrm{Hf}$ reaction cross sections the activation method was used. During irradiation the targets were arranged in stacks of four to reduce the required irradiation time. Aluminum degrader foils served as backings. The average interaction energy inside each ytterbium layer was determined via geant4 simulations. A third layer, consisting of manganese, was used to verify the simulations by comparing the measured ${}^{55}\mathrm{Mn}(\alpha ,(2\left)n\right){}^{57,58}\mathrm{Co}$ reaction cross sections to previous results. For irradiation the 10 MV FN tandem accelerator located at the University of Cologne was used and the activation measurement was performed utilizing the Cologne Clover Counting setup consisting of two clover-type high-purity germanium detectors in a face-to-face geometry.

Results: For the ${}^{170}\mathrm{Yb}(\alpha ,n)$ reaction seven cross sections at center-of-mass energies between 12.7 and 16.5 MeV were measured. For the ${}^{172}\mathrm{Yb}(\alpha ,n)$ reaction six cross sections for center-of-mass energies of 13.1 to 16.5 MeV could be determined with an additional upper limit at $E_{\mathrm{c}.\mathrm{m}.}=12.3$ MeV.

Conclusion: Comparisons to theoretical models show that state-of-the-art $\alpha$-optical model potentials reproduce the measured cross sections very well. The ratios of $(\alpha ,n)$ reaction cross sections in the ytterbium isotopic chain can be accurately reproduced as well.

$\alpha$ and cluster decays are analyzed for heavy nuclei located above ${}^{208}\mathrm{Pb}$ on the chart of nuclides: ${}^{216–220}\mathrm{Rn}$ and ${}^{220–224}\mathrm{Ra}$, which are also candidates for observing the $2\alpha$ decay mode. A microscopic theoretical approach based on relativistic energy density functionals (EDF), is used to compute axially symmetric deformation-energy surfaces as functions of quadrupole, octupole, and hexadecupole collective coordinates. Dynamical least-action paths for specific decay modes are calculated on the corresponding potential-energy surfaces. The effective collective inertia is determined using the perturbative cranking approximation, and zero-point and rotational energy corrections are included in the model. The predicted half-lives for $\alpha$ decay are within one order of magnitude of the experimental values. In the case of single-$\alpha$ emission, the nuclei considered in the present study exhibit least-action paths that differ significantly up to the scission point. The differences in $\alpha$-decay lifetimes are not only driven by $Q$ values, but also by variances of the least-action paths prior to scission. In contrast, the $2\alpha$ decay mode presents very similar paths from equilibrium to scission, and the differences in lifetimes are mainly driven by the corresponding $Q$ values. The predicted ${}^{14}\mathrm{C}$ cluster decay half-lives are within three orders of magnitudes of the empirical values, and point to a much more complex pattern compared with the $\alpha$-decay mode.

We have investigated the charge-dependent anisotropic flow in high-energy heavy-ion collisions, using relativistic resistive magneto-hydrodynamics (RRMHD). We consider the optical Glauber model as an initial model of the quark-gluon plasma (QGP) and the solution of the Maxwell equations with source term of the charged particles in two colliding nuclei as initial electromagnetic fields. The RRMHD simulation is performed with these initial conditions in Au-Au and Cu-Au collisions at $\sqrt{s_{NN}}=200$ GeV. We have calculated the charge-odd contribution to the directed flow $\mathrm{\Delta }{v}_1$ and elliptic flow $\mathrm{\Delta }{v}_2$ in both collisions based on electric charge distributions as a consequence of RRMHD. Our results show that the $\mathrm{\Delta }{v}_1$ and $\mathrm{\Delta }{v}_2$ are approximately proportional to the electrical conductivity ($\sigma$) of the medium. In the $\sigma =0.023{\mathrm{fm}}^{-1}$ case, our result of $\mathrm{\Delta }{v}_1$ is close to STAR data in Au-Au collisions, while it is slightly overestimated in forward and backward rapidity regions. Furthermore, in Cu-Au collisions, $\mathrm{\Delta }{v}_1$ has a nonzero value at $\eta =0$. We conclude that the charge-dependent anisotropic flow is a good probe to extract the electrical conductivity of the QGP medium in high-energy heavy-ion experiments.

Previous extensive studies on the dependence of the average transverse momentum, its slope as a function of the hadron mass, and the average transverse expansion on the particle multiplicity per unit rapidity and unit transverse overlap area of the colliding partners are extended to the ratio of the energy density to the entropy density. The behavior of the ratio between the average transverse momentum and the square root of the particle multiplicity per unit rapidity and unit transverse overlap area $\langle p_T\rangle /\sqrt{\langle dN/dy\rangle /S_{\perp }}$ as a function of collision energy for a given centrality or as a function of centrality for a given collision energy supports the predictions of color glass condensate and percolation based approaches. The dependence of the ratio of the energy density $\langle d{E}_T/dy\rangle /S_{\perp }$ to the entropy density $\langle dN/dy\rangle /S_{\perp }$ at different collision centralities for $A\text{−}A$ collisions from the Alternating Gradient Synchrotron, the Super Proton Synchrotron, the BNL Relativistic Heavy Ion Collider, and the CERN Large Hadron Collider energies is presented. The trend of this ratio towards a plateau at the highest RHIC energies followed by a steep rise at LHC energies is in agreement with theoretical predictions made 40 years ago that indicate this behavior as a signature of a phase transition. This pattern strongly depends on the collision geometry, converging towards the dependence that characterizes the $pp$ minimum bias collisions for the most peripheral $A\text{−}A$ collisions. Expected similarities between $pp$ and Pb-Pb collisions at LHC energies are confirmed.

We calculate the baryon number cumulants within acceptance with short-range correlations and global baryon number conservation in terms of cumulants in the whole system without baryon conservation. We extract leading and next-to-leading order terms of the large baryon number limit approximation. These approximations are checked to be very close to the exact results.

We compute bottomonium suppression and elliptic flow within the potential nonrelativistic quantum chromodynamics effective field theory using an open quantum systems approach. For the hydrodynamical background, we use $2+1\text{D}$ MUSIC second-order viscous hydrodynamics with IP-glasma initial conditions and evolve bottom/antibottom quantum wave packets in real time in these backgrounds. We find that the impact of fluctuating initial conditions is small when compared to results obtained using smooth initial conditions. Including the effect of fluctuating initial conditions, we find that the $\mathrm{{\rm Y}}\left(1S\right)$ integrated elliptic flow is $v_2\left[1S\right]=0.005\pm 0.002\pm 0.001$, with the first and second variations corresponding to statistical and systematic theoretical uncertainties, respectively.