Isospin-symmetry breaking is responsible for the energy difference of excited states in mirror nuclei. It also influences the coefficient of the isobaric multiplet mass equation. In the present work, we extensively investigate isospin-symmetry breaking in medium-mass nuclei within ab initio frameworks. For this, we employ the ab initio valence-space in-medium similarity renormalization group approach, in which charge-symmetry and charge-independence breakings are included in the adopted nuclear force. The mirror energies of $sd$- and $pf$-shell nuclei are computed for that matter. The effects of single-particle states on weakly bound and unbound nuclear states, especially those of the $s$ wave, are discussed. Predictions are also made concerning proton drip-line nuclei bearing large mirror energy difference. Finally, the coefficient of the isobaric multiplet mass equation in $T=1/2$ and $T=1$ isospin multiplets for $A=18$ to $A=76$ is calculated.

The saddle-to-scission dynamics of the induced fission process is explored using a microscopic finite-temperature model based on time-dependent nuclear density functional theory (TDDFT), that allows one to follow the evolution of local temperature along fission trajectories. Starting from a temperature that corresponds to the experimental excitation energy of the compound system, the model propagates nucleons along isentropic paths toward scission. For the four illustrative cases of induced fission of ${}^{240}\mathrm{Pu}, {}^{234}\mathrm{U}, {}^{244}\mathrm{Cm}$, and ${}^{250}\mathrm{Cf}$, characteristic fission trajectories are considered, and the partition of the total energy into various kinetic and potential energy contributions at scission is analyzed, with special emphasis on the energy dissipated along the fission path and the prescission kinetic energy. The model is also applied to the dynamics of neck formation and rupture, characterized by the formation of few-nucleon clusters in the low-density region between the nascent fragments.

We investigate the isospin transport with ${}^{40,48}\mathrm{Ca}+{}^{40,48}\mathrm{Ca}$ reactions at 35 MeV/nucleon, measured with the coupling of the VAMOS high acceptance spectrometer and the INDRA charged particle multidetector. Using the fragment measured with VAMOS and carefully selected light-charged-particles measured in coincidence with INDRA, a reconstruction method is applied to estimate the excited quasiprojectile (QP) on an event-by-event basis. Isospin diffusion is investigated using the isospin transport ratio with the asymmetry $\delta =(N-Z)/A$ of the projectile remnant as an isospin-sensitive observable and the total transverse energy of $Z\le 2$ nuclei for experimental centrality sorting. The experimental isospin transport ratios present, for both the reconstructed QP and its remnant, a clear evolution towards isospin equilibration with increasing dissipation of the collision while the full equilibration is not reached. A smoother evolution with less discrepancies between the two mixed systems in the case of the reconstructed QP is also observed. Isospin migration is investigated using the average neutron-to-proton ratio of the light-charged-clusters and the velocity of the QP remnant as a sorting parameter. A systematic neutron-enrichment is observed and interpreted as a consequence of isospin migration, in particular for the symmetric systems which present no isospin gradient between the projectile and the target. We also noticed that the ${}^2\mathrm{H}$ and ${}^4\mathrm{He}$ particles exhibit very close multiplicities independently of the sorting variable for the symmetric systems.

The hard proton knock-out by the proton from the deuteron at relativistic energies is considered with a focus on the color transparency (CT) effect which influences the initial- and final-state interactions. The calculations are performed in the framework of the generalized eikonal approximation supplemented by the quantum diffusion model of CT. The main results of the previous calculations [Frankfurt et al., Phys. Rev. C 56, 2752 (1997)] at the beam momentum below 20 $\mathrm{GeV}/\mathrm{c}$ are confirmed, including the dependence of the nuclear transparency on the transverse momentum of the spectator neutron, $p_{st}$, and on the relative azimuthal angle $\varphi$ between proton and neutron: absorption at $p_{st}<0.2\mathrm{GeV}/\mathrm{c}$ and enhancement at $p_{st}>0.3\mathrm{GeV}/\mathrm{c}$ due to rescattering on the neutron, the change of $\varphi$ dependence between these two regions, and the enhancement of CT effects with $p_{\mathrm{lab}}$. The study is then generalized to higher beam momenta, up to 75 $\mathrm{GeV}/\mathrm{c}$. It is shown that such behavior of the transparency is mainly preserved up to $p_{\mathrm{lab}}\simeq 50\mathrm{GeV}/\mathrm{c}$, but changes significantly at higher beam momenta due to the interference of valence quark configurations of small and large sizes. As a result, the transparency at small $p_{st}$ exhibits oscillations as a function of the beam momentum (the nuclear filtering effect). The tensor analyzing power due to the longitudinal polarization of the deuteron is calculated. The event rate at Nuclotron-based Ion Collider fAcility (NICA) is estimated.

The use of charge balance functions in heavy-ion collision studies was initially proposed as a probe of delayed hadronization and two-stage quark production in these collisions. It later emerged that general balance functions can also serve as a probe of the diffusivity of light quarks as well as the evolution of the systems formed in heavy-ion collisions. In this work, we reexamine the formulation of general balance functions and consider how to best define and measure these correlation functions in terms of differences of conditional densities of unlike-sign and like-sign particle pairs. We define general balance functions in terms of associated particle functions and show that these obey a simple sum rule. We additionally proceed to distinguish between balance functions expressed as differences of conditional densities valid irrespective of experimental acceptance boundaries and bound balance functions that explicitly account for the limited acceptance of experiments. General balance functions are additionally extended to accommodate strange, baryon, as well as charm and bottom quantum numbers based on the densities of these quantum numbers.

New results for the exclusive and quasifree cross sections off neutrons bound in deuterium ${\gamma }_{v}n\left(p\right)\to p{\pi }^{-}\left(p\right)$ are presented over a wide final state hadron angle range with a kinematic coverage of the invariant mass ($W$) up to 1.825 GeV and the four-momentum transfer squared ($Q^2$) from 0.4 to 1.0 ${\mathrm{GeV}}^2$. The exclusive structure functions were extracted and their Legendre moments were obtained. Final-state-interaction contributions have been kinematically separated from the extracted quasifree cross sections off bound neutrons solely based on the analysis of the experimental data. These new results will serve as long-awaited input for phenomenological analyses to extract the $Q^2$ evolution of previously unavailable $n\to N^{*}$ electroexcitation amplitudes and to improve state-of-the-art models of neutrino scattering off nuclei by augmenting the already available results from free protons.

The need to reconcile our understanding of the behavior of hadronic matter across a wide range of densities, especially at the time when data from multimessenger observations and novel experimental facilities are flooding in, has provided new challenges to the nuclear models. Particularly, the density dependence of the isovector channel of the nuclear energy functionals seems hard to pin down if experiments like PREX-II (or PREX) and CREX are required to be taken on the same footing. We put to test this anomaly in a semiagnostic modeling technique by performing a full Bayesian analysis of static properties of neutron stars, together with global properties of nuclei as binding energy, charge radii and neutron skin calculated at the semiclassical level. Our results show that the interplay between bulk and surface properties, and the importance of high-order empirical parameters that effectively decouple the subsaturation and the supersaturation density regime, might partially explain the tension between the different measurements and observations. If the surface behaviors, however, are decoupled from the bulk properties, then we found a rather harmonious situation among experimental and observational data.

We propose a possible scheme to interpret the complex expectation values associated with resonances having complex eigenenergies. Using the Green's function for resonances, the expectation value is basically described by the Breit-Wigner distribution as a function of the real excitation energy. In the expression of the complex expectation values for resonances, the real part brings the integral value of the distribution, while the imaginary part produces the deviation from the Breit-Wigner distribution, which explains a shift of the peak in the strength from the resonance energy. We apply the present scheme to several nuclear resonances of ${}^{12}\mathrm{C}$, including the Hoyle state, and neutron/proton-rich nuclei of ${}^6\mathrm{He}, {}^6\mathrm{Be}, {}^8\mathrm{He}$, and ${}^8\mathrm{C}$. In these nuclei, many-body resonances are obtained as the complex-energy eigenstates under the correct boundary condition using the complex scaling method, and their nuclear radii are uniquely evaluated. We discuss the peculiar energy dependence of the strength function of the square radius for the resonances in these nuclei.

We construct a dynamical model for high-energy heavy-ion collisions based on the relativistic resistive magneto-hydrodynamic framework. Using our newly developed ($3+1$)-dimensional relativistic resistive magneto-hydrodynamics code, we investigate magneto-hydrodynamic expansion in symmetric and asymmetric collision systems as the first application to high-energy heavy-ion collisions. As a realistic initial condition for electromagnetic fields, we consider the solutions of the Maxwell equations with the source term of point charged particles moving in the direction of the beam axis, including finite constant electrical conductivity of the medium. We evaluate the directed flow in the symmetric and asymmetric collisions at BNL Relativistic Heavy Ion Collider energy. We find a significant effect of finite electrical conductivity on the directed flow in the asymmetric collision system. We confirm that a certain amount of energy transfer by dissipation associated with Ohmic conduction occurs in the asymmetric collision system because of the asymmetry of the electric field produced by two different colliding nuclei. Because this energy transfer makes the pressure gradient of the medium flatter, the growth of directed flow decreases.

Forward recoil range distributions of evaporation residues produced in the system ${}^{19}\mathrm{F}+{}^{154}\mathrm{Sm}$ were measured at projectile energy $\approx 107$ MeV using the offline $\gamma$-ray activation technique. The entire and fractional linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The forward recoil range distributions of measured evaporation residues populated through $x\mathrm{n}/\mathrm{p}x\mathrm{n}$ channels were found to be consisting of a single peak only while the evaporation residues populated through $\alpha$ emitting channel had contributions from incomplete fusion also. The observed incomplete fusion process in the population of $\alpha$ emitting channel residues is explained through the breakup fusion model. The results indicate the occurrence of incomplete fusion involving the breakup of ${}^{19}\mathrm{F}$ into ${}^4\mathrm{He}+{}^{15}\mathrm{N}$ and/or ${}^8\mathrm{Be}+{}^{11}\mathrm{B}$ followed by fusion of one of the fragments with target nucleus ${}^{154}\mathrm{Sm}$. From these measurements, the relative contributions of complete and incomplete fusion were separated out. The forward recoil range distributions data show that the incomplete fusion contribution in the fusion of fragment ${}^{15}\mathrm{N}$ is more dominant as compared to the fusion of fragment ${}^{11}\mathrm{B}$ with ${}^{154}\mathrm{Sm}$ target due to the smaller value of $\alpha$ breakup threshold energy $\left(E_{\mathrm{B}.\mathrm{U}.}^{\alpha }\right)$. The measured forward recoil range distributions of evaporation residues produced through $\alpha$ emitting channels provide experimental signature of strong clustering in ${}^{19}\mathrm{F}$ projectile as $\alpha$ and ${}^{15}\mathrm{N}$. The incomplete fusion strength function has also been deduced from the measured recoil range distributions and found to be compatible with those deduced from the measured excitation functions for the same system and beam energy.

Optical-model potentials (OMPs) continue to play a key role in nuclear reaction calculations. However, the uncertainty of phenomenological OMPs in widespread use—inherent to any parametric model trained on data—has not been fully characterized, and its impact on downstream users of OMPs remains unclear. Here we assign well-calibrated uncertainties for two representative global OMPs, those of Koning-Delaroche and Chapel Hill '89, using Markov-chain Monte Carlo for parameter inference. By comparing the canonical versions of these OMPs against the experimental data originally used to constrain them, we show how a lack of outlier rejection and a systematic underestimation of experimental uncertainties contributes to bias of, and overconfidence in, best-fit parameter values. Our updated, uncertainty-quantified versions of these OMPs address these issues and yield complete covariance information for potential parameters. Scattering predictions generated from our ensembles show improved performance both against the original training corpora of experimental data and against a new “test” corpus comprising many of the experimental single-nucleon scattering data collected over the last twenty years. Finally, we apply our uncertainty-quantified OMPs to two case studies of application-relevant cross sections. We conclude that, for many common applications of OMPs, including OMP uncertainty should become standard practice. To facilitate their immediate use, digital versions of our updated OMPs and related tools for forward uncertainty propagation are included as Supplemental Material.

Projectile fragmentation provides an method to produce the unknown neutron-rich isotopes. In this work, the isospin-dependent Boltzmann-Langevin equation is employed to investigate the influence of projectiles on the fragments production. The cross sections of fragments with proton number $Z=20$–27 are calculated under the reaction systems ${}^{81,84,86}\mathrm{Ga}+{}^9\mathrm{Be}$. The obtained results suggest that the radioactive projectile ${}^{86}\mathrm{Ga}$ is favorable to the yields of neutron-rich nuclei. The newly produced isotopes ${}^{61}\mathrm{Ca}, {}^{63}\mathrm{Sc}, {}^{65}\mathrm{Ti}, {}^{68,69}\mathrm{V}, {}^{71}\mathrm{Cr}, {}^{77}\mathrm{Fe}$, and ${}^{79}\mathrm{Co}$, whose cross sections are characterized by the order of 1 to 100 $\mu \mathrm{b}$, can be observed in the reaction ${}^{86}\mathrm{Ga}+{}^9\mathrm{Be}$ at $1A$ GeV. This means the production cross sections of neutron-rich nuclei are very highly sensitive to the neutron-proton excess of projectile.

In-medium nucleon-nucleon ($NN$) cross sections at various densities and isospin asymmetries are investigated systematically in the framework of the Brueckner-Hartree-Fock approach. The calculations are base on the exact treatment of the center-of-mass momentum instead of the total momentum approximation employed in previous works. The neutron-proton in-medium cross section is shown to exhibit nearly isospin asymmetry independence. For convenience in application, analytical formulas embodying the medium correction to free $NN$ cross section with parameters calibrated to the calculated results have been provided. Using these formulas, the transverse and elliptic flows of emitted nucleons in heavy-ion collisions are studied within the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model. We find the medium effect of the cross section from the $G$ matrix contributes to the transverse and elliptic flows oppositely to and obviously smaller than that from the effective mass. In addition, the present microscopic in-medium cross sections can significantly revise the predictions of the transverse and elliptic flows compared to the in-medium cross sections previously adopted in transport models for heavy-ion collisions.

Excited states in ${}^{92}\mathrm{Mo}$ are populated via the ${}^{89}\mathrm{Y}({}^6\mathrm{Li},3n){}^{92}\mathrm{Mo}$ reaction at the tandem of XTU, INFN-LNL. The level scheme of ${}^{92}\mathrm{Mo}$ is revised and expanded considerably by the $\gamma \text{−}\gamma$ coincidence measurement. The newly observed level structures are compared with different shell-model calculations performed in various model spaces. The results show that the several high-energy ($\approx 2$ MeV) transitions, observed for the first time in the current work, could be a presumable signature of $N=50$ core-breaking effect. The measured strengths of $E1$ transitions between the low-lying positive and negative bands indicate an important contribution from $Z=28$ proton core-excitation.

Background: To understand superheavy element synthesis reactions, quantifying the role of quantum shells in quasifission dynamics is important. In reactions with actinide nuclides, a wide peak in the binary quasifission mass yield is seen, centered close to the ${}^{208}\mathrm{Pb}$ mass. It is generally attributed to the ${}^{208}\mathrm{Pb}$ spherical closed shells causing a valley in the potential-energy surface, attracting flux to these mass splits. However, an early experiment studying ${}^{48}\mathrm{Ca}, {}^{50}\mathrm{Ti}+{}^{238}\mathrm{U}$ reactions showed strong evidence that sequential fission plays an important role in generating the observed peak. These conflicting interpretations have not been resolved up to now.

Purpose: This work aims to measure quasifission mass spectra for reactions with nuclei lighter than ${}^{208}\mathrm{Pb}$, having negligible sequential fission, to search for systematic features correlated with the proton shells known to affect low-energy fission mass distributions of the same actinide elements.

Methods: Systematic measurements have been made at energies near and below the capture barriers (where quasifission is most prominent) of mass-angle distributions for fission following collisions of ${}^{48}\mathrm{Ti}$ projectiles with even-even nuclides from ${}^{154}\mathrm{Sm}$ to ${}^{200}\mathrm{Hg}$. Mean excitation energies above the ground-states ranged from 51 to 33 MeV, respectively.

Results: With increasing compound nucleus atomic number ${\mathrm{Z}}_{CN}$, a rapid transition occurs from fission having characteristics of fusion-fission to fast quasifission. The heaviest reactions form ${}^{240}\mathrm{Cf}, {}^{244}\mathrm{Fm}$, and ${}^{248}\mathrm{No}$. Low-energy fission of neighboring isotopes is mass asymmetric, correlated with proton number $Z=56$. However, peak quasifission yields are at mass-symmetry for all reactions. There appears to be a very small ($\approx 3$%) systematic excess of yield correlated with $Z=56$, however this is at the limit of sensitivity of the experiment.

Conclusions: No significant ($>3\%$) systematic features are seen in the quasifission mass spectra that can be unambiguously identified as resulting from shells. This small influence may result from attenuation of shell effects due to the excitation energy introduced, even in these near-barrier reactions giving low excitation energies typical of superheavy element synthesis reactions.

The nucleonic localization function has been used for a decade to study the formation of $\alpha$ particles in nuclei, by providing a measure of having nucleons of a given spin in a single place. However, differences in interpretation remain, compared to the nucleonic density of the nucleus. In order to better understand the respective role of the nucleonic localization function and the densities in the $\alpha$-particle formation in cluster states or in the $\alpha$-decay mechanism, both an analytic approximation and microscopic calculations, using energy density functionals, are undertaken. The nucleonic localization function is shown to measure the anticentrifugal effect, and is not sensitive to the level of compactness of the $\alpha$ particle itself. It probes the purity of the spatial overlap of four nucleons in the four possible (spin, isospin) states. The density provides, in addition, information on the compactness of an $\alpha$-particle cluster. The respective roles of the nucleonic localization function and the density are also analyzed in the case of $\alpha$ particle emission. More generally, criteria to assess the prediction of $\alpha$ cluster in nuclear states are provided.

${}^{162}\mathrm{Er}$ is one of the $p$ nuclei in nuclear astrophysics, and its ($n,\gamma$) cross sections are important input parameters in nuclear astrophysics network calculations. Resonance data for ${}^{162}\mathrm{Er}(n,\gamma ){}^{163}\mathrm{Er}$ at 67.8 eV is currently not present in the EXFOR database; however, it is included in the ENDF/B VIII.0 database. The ($n,\gamma$) cross section of ${}^{\mathrm{nat}}\mathrm{Er}$ has been measured in the energy range of 1–100 eV at the Back-n facility in the China Spallation Neutron Source. However, due to the influence of the in-beam $\gamma$ background of the Back-n Facility, it is has not been possible to observe the neutron resonance peak of ${}^{162}\mathrm{Er}$ at 67.8 eV. A general simulation method is proposed for quantifying the in-beam $\gamma$-ray background. By subtracting the in-beam $\gamma$-ray background, the neutron-capture yields of ${}^{162}\mathrm{Er}$ are obtained within the energy range of 20–100 eV. The neutron resonance parameters of ${}^{162}\mathrm{Er}$ at 67.8 eV are then extracted successfully. It is found that ${\mathrm{\Gamma }}_{\gamma }=101.15\pm 10.08$ meV and ${\mathrm{\Gamma }}_n=2.79\pm 0.28$ meV, which are consistent with the ENDF/B VIII.0 database. However, the 51.4-eV resonance peak of ${}^{162}\mathrm{Er}(n,\gamma$) is currently unobserved.

Beta-delayed neutron emission and $\beta$-delayed fission ($\beta \mathrm{df}$) probabilities were calculated for heavy, neutron-rich nuclei using the Los Alamos coupled quasiparticle random-phase approximation plus Hauser-Feshbach ($\mathrm{QRPA}+\mathrm{HF}$) approach. In this model, the compound nucleus is initially populated by $\beta$ decay and is followed through subsequent statistical decays taking into account competition among neutrons, $\gamma$ rays, and fission. The primary output of these calculations includes branching ratios along with neutron and $\gamma$-ray spectra. We find a relatively large region of heavy nuclides where the probability of $\beta \mathrm{df}$ is near 100%. For a subset of nuclei near the neutron drip line, delayed neutron emission and the probability of fission are both large, which leads to the possibility of multichance $\beta \mathrm{df}$ (mc-$\beta \mathrm{df}$). We comment on prospective neutron-rich nuclei that could be probed by future experimental campaigns and provide a full table of branching ratios in ASCII format in the Supplemental Material for use in various applications.