The sum-rule approach and the shell model are used to estimate the energies of Gamow-Teller (GT) giant resonances in high-spin isomeric (HSI) states in $N=Z$ nuclei. The newly derived energy-weighted sum rules show that the GT resonance energies of HSI states are related to the $\sigma \sigma \tau \tau$ and $\sigma \sigma$ interactions. Comparing the results of the sum-rule approach with those of large-scale shell-model calculations for the ${}^{52}\mathrm{Fe}\left({12}^{+}\right)$ and ${}^{94}\mathrm{Ag}\left({21}^{+}\right)N=Z$ high-spin isomers, the deduced ${\kappa }_{\sigma }$, which is the strength of the $\sigma \sigma$ residual interaction in a simple residual-interaction model, is 2.5 MeV.

Quasielastic scattering excitation function at large backward angle has been measured for the weakly bound system ${}^7\mathrm{Li}+{}^{159}\mathrm{Tb}$ at energies around the Coulomb barrier. The corresponding quasielastic barrier distribution has been derived from the excitation function, both including and excluding the $\alpha$ particles produced in the reaction. The centroid of the barrier distribution obtained after inclusion of $\alpha$ particles was found to be shifted higher in energy, compared with the distribution excluding the $\alpha$ particles. The quasielastic data, excluding the $\alpha$ particles, have been analyzed in the framework of continuum discretized coupled-channels calculations. The quasielastic barrier distribution for ${}^7\mathrm{Li}+{}^{159}\mathrm{Tb}$, has also been compared with the fusion barrier distribution for the system.

For photoproduction reactions with final states consisting of two pseudoscalar mesons and a spin-1/2 baryon, eight complex amplitudes need to be determined uniquely. A modified version of Moravcsik's theorem is employed for these reactions, resulting in slightly overcomplete sets of polarization observables that are able to determine the amplitudes uniquely. Further steps were taken to reduce the found sets to minimal complete sets. As a final result, multiple minimal complete sets without any remaining ambiguities are presented for the first time. These sets consist of $2N=16$ observables, containing only one triple polarization observable.

Background: In heavy-ion fusion reactions, the compound nucleus' de-excitation process is observed via two competitive modes, evaporation of particles and fission, at relatively higher excitation energies. Although fusion-fission dynamics have been extensively studied in actinide nuclei, exploration of the same is yet to come for preactinide nuclei.

Purpose: The objective is to understand the fusion-fission dynamics involved in the ${}^{11}\mathrm{B}+{}^{181}\mathrm{Ta}$ reaction within 4.8–5.7 MeV/nucleon energy by measuring absolute cross sections of the residues, which are mainly populating through complete and incomplete fusion-evaporation (FE), pre-equilibrium (PEQ), and fusion-fission (FF) mechanisms, as well as to infer on the mass and charge distributions of fission fragments.

Method: The stacked-foil activation technique was employed, followed by off-line $\gamma$-ray spectroscopy, to measure the activity and production cross sections of radionuclides populated through FE and FF. Charge and mass distributions were studied to obtain dispersion parameters of fission fragments.

Results: The equilibrium and pre-equilibrium reaction models have been used to analyze residual cross-section data resulting from FE and PEQ processes in the framework of EMPIRE3.2.2 and PACE4 codes. PEQ reaction's strengths in $3n$-channel have been extracted and compared with other systems. The relative distribution of spins between the ground and isomeric state of ${}^{186}\mathrm{Ir}$ has been discussed in view of the measured isomeric cross-section ratios. Further, 22 fission-fragments have been identified within the mass range $24\le A\le 160$. The variance extracted from the measured isotopic yield distributions of Nd isotopes is in good agreement with the literature values. A well-consistent approach has been employed to determine the isobaric yield distribution of Nd and In isotopes.

Conclusion: The combination of Hauser-Feshbach formalism for compound evaporation and the Exciton model for PEQ reaction agrees with the measured data of $xn$-channel residues, which confirms their production from the CF mechanism. Indirect evidence of ICF was observed in the $\alpha$- and $p$-emitting channels. Further, fission fragments' mass distribution is broad and symmetric, indicating their production through the compound nuclear mechanism. The variance of fission fragments' mass distribution shows an increasing trend with raising excitation energy.

The evaluation of the subsaturation nuclear equation of state at finite temperature requires a proper state counting of the internal partition sum of nuclei which are immersed in the background of their continuum states. This classical statistical problem is addressed within the self-consistent mean-field approximation, which naturally accounts for isospin and effective mass effects in the nuclear density of states. The nuclear free energy is decomposed into bulk and surface terms, allowing a simple analytical prescription for the subtraction of gas states from the nuclear partition sum, that avoids double counting of unbound single-particle states. We show that this correction leads to a sizable effect in the composition of matter at high temperature and low proton fractions, such as is formed in supernova collapse, early proto-neutron-star evolution, as well as laboratory experiments. Specifically, the energy stored in the internal nuclear degrees of freedom is reduced, as well as the mass fraction of heavy clusters in the statistical equilibrium. The gas subtraction prescription is compared with different phenomenological methods proposed in the literature, based on a high-energy truncation of the partition sum. We show that none of these methods satisfactorily reproduces the gas subtracted level density, if the temperature overcomes $\approx 4$ MeV.

We study the impact of strong magnetic fields on the pasta phases that are expected to exist in the inner crust of neutron stars. We employ the relativistic mean field model to describe the nucleon interaction and use the self-consistent Thomas-Fermi approximation to calculate the nonuniform matter in neutron star crust. The properties of pasta phases and crust-core transition are examined. It is found that as the magnetic field strength $B$ is less than ${10}^{17}$ G, the effects of magnetic field are not evident comparing with the results without magnetic field. As $B$ is stronger than ${10}^{18}$ G, the onset densities of pasta phases and crust-core transition density decrease significantly, and the density distributions of nucleons and electrons are also changed obviously.

Properties of the liquid-gas (LG) phase transition of thermal nuclear matter are investigated within the relativistic Hartree-Fock (RHF) theory, focusing on the role played by the in-medium balance between nuclear attraction and repulsion. Applying the RHF Lagrangian PKA1, rather different critical properties and LG phase diagrams are obtained in contrast to the other popular relativistic Lagrangians. Aiming at such notable model deviations, a series of testing parametrizations $x{\kappa }_{\rho }$ (${\kappa }_{\rho }$ being the $\rho$-tensor coupling strength) are proposed to bridge PKA1 and other popular Lagrangians. Along the systematics from PKA1 to the $x{\kappa }_{\rho }$ series and further to other popular Lagrangians, it is illustrated that the in-medium balance of nuclear attraction and repulsion, manifested as various modeling of the nuclear in-medium effects, is essential for the van der Waals-like behaviors of thermal nuclear matter, in which the residual nuclear in-medium effects deduced from the dominant attractive and repulsive channels play a significant role. Our study paves a way to model the in-medium nuclear interactions from the thermal statistic aspects of nuclear systems, e.g., referring to the critical temperature from future delicate experiments.

Experimental data concerning isospin transport phenomena for the systems ${}^{80}\mathrm{Kr}+{}^{40,48}\mathrm{Ca}$ at 35 MeV/nucleon are presented. Data have been collected with four FAZIA blocks; this data set is the same analyzed in S. Piantelli et al., Phys. Rev. C 101, 034613 (2020). The isotopic composition of the QuasiProjectile residue (up to $Z$ around 25) and of its decay products in the two reactions are compared, finding a neutron enrichment when the target is ${}^{48}\mathrm{Ca}$. The isotopic composition of the emitted light charged particles (LCP) and intermediate mass fragments (IMF) was also investigated in different windows of velocity. The obtained results have been compared with the prediction of the transport model AMD followed by the statistical code GEMINI (used as an afterburner), with different recipes for the density dependence of the symmetry energy term in the nuclear equation of state. A weak indication in favor of a stiff symmetry energy emerges when the fragments emitted at midvelocity are examined.

Background: The problem of the scattering of a one-neutron halo nucleus by another nucleus might involve an extremely complicated solution, particularly when breakup and rearrangement channels are to be considered.

Purpose: We construct a simple model to study the evolution of a single-particle wave function during the collision of a one-dimensional potential well by another well.

Method: Our one-dimensional model provides the essential three-body nature of this problem, and allows for a much simpler application and assessment of different methods of solution. To simplify further the problem, we assume that the potential well representing the projectile moves according to a predetermined classical trajectory, although the internal motion of the “valence” particle is treated fully quantum mechanically. This corresponds to a semiclassical approach of the scattering problem, applicable in the case of heavy projectile and target. Different approaches are investigated to understand the dynamics involving one-body halo-like systems: the “exact” time-dependent solution of the Schrödinger equation is compared to a numerical continuum-discretized coupled-channels (CC) calculation presenting various model cases including different reaction channels.

Results: This framework allows us to discuss the reaction mechanism and the role of the continuum, the inclusion of which in the CC calculation results to be crucial to reproduce the exact solution, even when the initial and final states are well bound.

Conclusions: The dynamical situations under study can be linked to analogous problems solved in a three-dimensional (3D) CC framework, so the present model provides a simple tool to understand the main challenges experienced in the usual 3D models with the treatment of the continuum.

The neutron-proton (n-p) equilibration process in ${}^{48}\mathrm{Ca}+{}^{40}\mathrm{Ca}$ at 35 MeV/nucleon bombarding energy is experimentally estimated by means of the isospin transport ratio. Experimental data are collected with a subset of the FAZIA telescope array, which permits us to determine the $Z$ and $N$ of detected fragments. For the first time, the quasiprojectile (QP) evaporative channel is compared with the QP breakup one in a homogeneous and consistent way, pointing to comparable n-p equilibration, which suggests a close interaction time between projectile and target independently of the exit channel. Moreover, in the QP evaporative channel n-p equilibration is compared with the prediction of the antisymmetrized molecular dynamics model coupled with the Gemini statistical model as an afterburner, showing a higher probability of proton and neutron transfers in the simulation with respect to the experimental data.

We investigate the influence of chiral symmetry which varies along the space-time evolution of a system, by considering the chiral phase transition in a nonequilibrium expanding quark-antiquark system. The chiral symmetry is described by the mean field order parameter, whose value is the solution of a self-consistent equation, and affects the space-time evolution of the system through the force term in the Vlasov equation. The Vlasov equation and the gap equation are solved concurrently and continuously for a longitudinal boost-invariant and transversely rotation-invariant system. This numerical framework enables us to carefully investigate how the phase transition and collision affect the evolution of the system. It is observed that the chiral phase transition gives rise to a kink in the flow velocity, which is caused by the force term in the Vlasov equation. The kink is enhanced by larger susceptibility and tends to be smoothed out by nonequilibrium effects. The spatial phase boundary appears as a “wall” for the quarks, as the quarks with low momentum are bounced back, while those with high momentum go through the wall but are slowed down.

Nuclear reactions of interest for astrophysics and applications often rely on statistical model calculations for nuclear reaction rates, particularly for nuclei far from $\beta$ stability. However, statistical model parameters are often poorly constrained, where experimental constraints are particularly sparse for exotic nuclides. For example, our understanding of the breakout from the NiCu cycle in the astrophysical $rp$-process is currently limited by uncertainties in the statistical properties of the proton-rich nucleus ${}^{60}\mathrm{Zn}$. We have determined the nuclear level density of ${}^{60}\mathrm{Zn}$ using neutron evaporation spectra from ${}^{58}\mathrm{Ni}{(}^3\mathrm{He},n)$ measured at the Edwards Accelerator Laboratory. We compare our results to a number of theoretical predictions, including phenomenological, microscopic, and shell-model-based approaches. Notably, we find the ${}^{60}\mathrm{Zn}$ level density is somewhat lower than expected for excitation energies populated in the ${}^{59}\mathrm{Cu}(p,\gamma ){}^{60}\mathrm{Zn}$ reaction under $rp$-process conditions. This includes a level density plateau from roughly 5 to 6 MeV excitation energy, which is counter to the usual expectation of exponential growth and all theoretical predictions that we explore. A determination of the spin distribution at the relevant excitation energies in ${}^{60}\mathrm{Zn}$ is needed to confirm that the Hauser-Feshbach formalism is appropriate for the ${}^{59}\mathrm{Cu}(p,\gamma ){}^{60}\mathrm{Zn}$ reaction rate at x-ray burst temperatures.

Background: Idealized systems are commonly used in nuclear physics and condensed matter. For instance, the construction of nuclear energy density functionals involves properties of infinite matter, whereas neutron drops are used to test nuclear interactions and approximations to the nuclear many-body problem. In condensed matter, quantum rings are also used to study properties of electron systems.

Purpose: To investigate the possibility to use quantum rings with systems of nucleons including many-body correlations.

Methods: A quantum ring model of a finite number of same spin fermions is developed. Several attractive and repulsive interactions with finite and infinite ranges are considered. Quantum Monte Carlo calculations are used to provide exact ground-state energies. Comparisons with analytical Hartree-Fock solutions are used to get an insight into the role of correlations.

Results: Hartree-Fock results with no breaking of space translational symmetry are able to describe many systems. However, additional spatial correlations are required in the case of dense systems with a strong short-range repulsion or with attractive interactions in large rings.

Conclusions: Self-bound systems of fermions with spatial correlations produced by basic features of the nuclear interactions can be described on a quantum ring, encouraging applications with realistic interactions, as well as investigations with higher-dimensional geometries, such as spherium.

Backward elastic electron scattering from odd-$A$ nuclear targets is characterized by magnetic form factors containing precise information on the nuclear structure. We study the sensitivity of the magnetic form factors to structural effects related to the evolution and shape transitions in both isotopic and isotonic chains. Calculations of magnetic form factors are performed in the plane-wave Born approximation. The nuclear structure is obtained from a deformed self-consistent mean-field calculation based on a Skyrme $\mathrm{HF}+\mathrm{BCS}$ formalism. Collective effects are included in the cranking approximation, whereas nucleon-nucleon correlations are taken into account in the coherent density fluctuation model. The evolution of the magnetic form factors is found to exhibit signatures of shape transitions that show up in selected isotopic and isotonic chains involving both stable and unstable nuclei. Several cases are identified as suitable candidates for showing such fingerprints of shape transitions. A new generation of electron scattering experiments involving electron-radioactive beam colliders will be available in the near future, leading to a renewed interest in this field.

The production of neutron-rich isotopes and the occurrence of neutron capture cascades via laser-driven (pulsed) neutron sources are investigated theoretically. The considered scenario involves the interaction of a laser-driven neutron beam with a target made of a single type of seed nuclide. We present a comprehensive study over 95 seed nuclides in the range $3\le Z\le 100$ from ${}_3{}^7\mathrm{Li}$ to ${}_{100}{}^{255}\mathrm{Fm}$. For each element, the heaviest sufficiently long-lived (half-life $>1$ h) isotope whose data is available in the recent ENDF-B-VIII.0 neutron sublibrary is considered. We identify interesting seed nuclides with good performance in the production of neutron-rich isotopes where neutron capture cascades may occur. The effects of the neutron number per pulse, the neutron-target interaction size, and the number of neutron pulses are also analyzed. Our results show the possibility of observing up to four successive neutron capture events, leading to neutron-rich isotopes with four more neutrons than the original seed nuclide. This hints at experimental possibilities to produce neutron-rich isotopes and simulate neutron capture nucleosynthesis in the laboratory. With several selected interesting seed nuclides in the region of the branching point of the $s$-process $({}_{51}{}^{126}\mathrm{Sb},$ ${}_{71}{}^{176}\mathrm{Lu}, \mathrm{and} {}_{75}{}^{187}\mathrm{Re})$ or the waiting point of the $r$-process (Lu, Re, Os, Tm, Ir, and Au), we expect that laser-driven experiments can shed light on our understanding of nucleosynthesis.

The majorana demonstrator is a neutrinoless double-$\beta$ decay search consisting of a low-background modular array of high-purity germanium detectors, $\sim 2/3$ of which are enriched to 88% in ${}^{76}\mathrm{Ge}$. The experiment is also searching for double-beta decay of ${}^{76}\mathrm{Ge}$ to excited states (e.s.) in ${}^{76}\mathrm{Se}$. ${}^{76}\mathrm{Ge}$ can decay into three daughter states of ${}^{76}\mathrm{Se}$, with clear event signatures consisting of a $\beta \beta$-decay followed by the prompt emission of one or two $\gamma$ rays. This results with high probability in multi-detector coincidences. The granularity of the demonstrator detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9 kg yr of isotopic exposure, the demonstrator has set world leading limits for each e.s. decay of ${}^{76}\mathrm{Ge}$, with 90% CL lower half-life limits in the range of $(0.75–4.0)\times {10}^{24}$ yr. In particular, for the $2\nu$ transition to the first $0^{+}$ e.s. of ${}^{76}\mathrm{Se}$, a lower half-life limit of $7.5\times {10}^{23}$ yr at 90% CL was achieved.

The ${}^9\mathrm{Be}({}^3\mathrm{He},\alpha ){}^8\mathrm{Be}^{*}\left(p\right){}^7\mathrm{Li}$ reaction was studied at $E_{\mathrm{lab}}{(}^3\mathrm{He})=30$ MeV to deduce the branching ratios of ${\mathrm{\Gamma }}_{p1}$/${\mathrm{\Gamma }}_{p0}$ of resonant states at 18.91–20.1MeV in ${}^8\mathrm{Be}$, which are necessary to extract the ${}^7\mathrm{Be}(n,p_1){}^7\mathrm{Li}^{*}$ reaction rate relevant to the ${}^7\mathrm{Be}$ destruction in the big bang nucleosynthesis, from the ${}^7\mathrm{Li}(p,n_0){}^7\mathrm{Be}$ reaction cross section. The decay protons from ${}^8\mathrm{Be}^{*}$ to the ground and first excited states in ${}^7\mathrm{Li}$ were well-separately measured. The ${\mathrm{\Gamma }}_{p1}$/${\mathrm{\Gamma }}_{p0}$ ratio of the 19.235-MeV state was deduced to be $3.4\pm 1.9$ %. The 19.86- and 20.1-MeV states were found to decay dominantly into the first excited and ground states of ${}^7\mathrm{Li}$, respectively.

Albergo thermometers with double isotope, isotone, and isobar yield ratio pairs with one proton and/or neutron difference are investigated. Without any extra sequential decay correction, a real temperature value of $4.9\pm 0.5$ MeV is deduced from the yields of the experimentally reconstructed primary hot intermediate mass fragments (IMFs) from ${}^{64}\mathrm{Zn}+{}^{112}\mathrm{Sn}$ collisions at 40 MeV/nucleon using the Albergo thermometer for the first time. An experimental sequential decay correction from the apparent temperatures to the real ones for 12 other reaction systems with different neutron-proton ($N/Z$) asymmetries in the same experiment, ${}^{70}\mathrm{Zn}$, ${}^{64}\mathrm{Ni}$ on ${}^{112,124}\mathrm{Sn}$, ${}^{58,64}\mathrm{Ni}$, ${}^{197}\mathrm{Au}$, and ${}^{232}\mathrm{Th}$ at 40 MeV/nucleon, is performed using an empirical correction factor approach of Tsang et al. [Phys. Rev. Lett. 78, 3836 (1997)] with the deduced 4.9-MeV temperature value. The dependence of nuclear temperature on the source $N/Z$ asymmetry is further investigated using these deduced real source temperature values from the present 13 systems. It is found that the deduced real source temperatures at the present source $N/Z$ range show a rather weak dependence on the source $N/Z$ asymmetry. By comparison between our previous results and those from other independent experiments, a consistent description for the $N/Z$ asymmetry dependence of nuclear temperature is addressed.

High-spin states in ${}^{123}\mathrm{Xe}$ were populated in the ${}^{80}\mathrm{Se}({}^{48}\mathrm{Ca}, 5\mathrm{n}){}^{123}\mathrm{Xe}$ reaction at a beam energy of 207 MeV. $\gamma$-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus. The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov models. It is concluded that the configurations of the bands involve two-proton excitations across the $Z=50$ as well as excitation of neutrons across the $N=82$ shell gaps resulting in a large deformation, ${\varepsilon }_2\approx 0.30$ and $\gamma \approx 5^{\circ }$.