We have updated our previous multipoles model for the kaon photoproduction process $\gamma p\to K^{+}\mathrm{\Lambda }$ by using the recently available experimental data, including the new CLAS 2016 data, and up-to-date information on the nucleon resonance properties provided by the Particle Data Group (PDG). The background and resonance parameters are extracted by fitting the calculated observables to nearly 7400 experimental data points and constraining the resonance parameters within the PDG error bars. The model can nicely reproduce the experimental data with ${\chi }^2/N_{\mathrm{dof}}=1.63$. Different from the previous result, the present analysis finds the $N\left(1650\right)S_{11}, N\left(1720\right)P_{13}$, and $N\left(1900\right)P_{13}$ states to be the most important resonances in the process. Excluding these states in the model increases the value of ${\chi }^2$ tremendously. As in our previous model, however, the contribution of the $N\left(1710\right)P_{11}$ state in minimizing ${\chi }^2$ is found to be less significant. By including the new CLAS 2016 data in the fitting database and refitting the calculated observables to nearly 9000 data points, the ${\chi }^2/N_{\mathrm{dof}}$ increases to 2.88. In spite of the increase of ${\chi }^2$, the agreement of model calculations with the new data is improved and the conclusion on the most important resonances in the process remains the same. An extensive comparison between the result of model calculations and experimental data on differential cross section, single polarization observables $P, T$, and $\mathrm{\Sigma }$, as well as double polarization observables $C_x, C_z, O_{x^{\prime }}, O_{z^{\prime }}, O_x$, and $O_z$, is presented in this paper.

We investigate the ${\eta }^{\prime }$ photoproduction off the nucleon with a particular interest in the effect of the final-state interaction (FSI) of the ${\eta }^{\prime }$ meson and nucleon $\left({\eta }^{\prime }N\right)$ based on the three-flavor linear $\sigma$ model. We find an enhancement in the cross section of the ${\eta }^{\prime }$ photoproduction near the ${\eta }^{\prime }N$-threshold energy owing to the ${\eta }^{\prime }N$ FSI. With the ${\eta }^{\prime }$ meson at forward angles, the energy dependence near the ${\eta }^{\prime }N$ threshold is well reproduced with the ${\eta }^{\prime }N$ FSI. The cross section at backward angles can also be a good probe to investigate the strength of the ${\eta }^{\prime }N$ interaction.

We have studied the effect of free space nucleon radius on the nuclear matter and slowly rotating neutron-star properties within a relativistic mean-field model with the inclusion of $\omega -\rho$ mixing nonlinear term. We use the same density-dependent radius as in our previous work. However, in the present work, we utilize the parameter sets with more proper symmetric nuclear matter (SNM) predictions for a number of different nucleon radii. To this end, the isoscalar parameters in each parameter set and the cutoff parameter $\beta$ are adjusted by fitting the corresponding SNM properties at subsaturation density to the prediction of IUFSU parameter set. Our results show that the assumption of composite nucleons with free space radius $r\le 0.83$ fm is still compatible with the currently acceptable nuclear matter (NM) properties beyond the saturation density. We have also found that the effect of free space nucleon radius could be imprinted in the radius, moment of inertia, and crust properties of the slowly rotating neutron star.

The drift of the isospin degree of freedom (IDOF) is experimentally visualized through the wide-range angular distribution and the beam energy dependence of the isospin composition of light charged particles (LCP) produced in heavy ion collisions. It is evidenced that the net isospin transport is presented in the whole process from early dynamic emission to the statistical evaporation lasting to very late stage. Due to the long-time accumulation of the isospin effect, the angular distribution of the relative neutron excess summing over the LCPs is utilized as a sensitive probe to the symmetry energy. With $S$ fixed at 28.3 MeV, a soft density dependence with $L=33\text{–}61$ MeV (0.95 confidential level) at ${\rho }_0$ is circumstantially deduced using an improved quantum molecular dynamics transport model attached with a statistical emission afterburner.

We report measurements of the photon beam asymmetry $\mathrm{\Sigma }$ for the reactions $\vec{\gamma }p\to p{\pi }^0$ and $\vec{\gamma }p\to p\eta$ from the GlueX experiment using a 9 GeV linearly polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous ${\pi }^0$ measurements and are the first $\eta$ measurements in this energy regime. The results are compared with theoretical predictions based on $t$-channel, quasiparticle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models.

The nuclear force has been understood to have a repulsive core at short distances, similar to a molecular force, since Jastrow proposed it in 1951 [R. Jastrow, Phys. Rev. 81, 165 (1951)]. The existence of the repulsion was experimentally confirmed from the proton-proton scattering ${}^{1}S_0$ phase shift, which becomes negative beyond 230 MeV. This repulsion is essential for preventing the nucleon-nucleon system from collapsing by attraction. The origin of the repulsion has been considered to be due to the Pauli principle, similar to the repulsion originally revealed in $\alpha -\alpha$ scattering, in many studies including recent lattice QCD calculations. On the other hand, very recently it was shown that an internuclear potential including $\alpha -\alpha$ interactions has a Luneburg-lens-like attraction at short distances rather than repulsion. I show that the nuclear force with an attractive potential at short distances that reproduces the experimental ${}^{1}S_0$ phase shifts well has a Luneburg-lens-like structural Pauli attractive core at short distances and acts as apparent repulsion. The apparent repulsion is caused by the deeply embedded unobservable Pauli forbidden state similar to nucleus-nucleus potentials.

Background: Transfer reactions are a useful tool for studying nuclear structure, particularly in the regime of low level densities and strong single-particle strengths. In addition, transfer reactions can populate levels above particle decay thresholds, allowing for the possibility of studying the subsequent decays and furthering our understanding of the nuclei being probed. In particular, the decay of loosely bound nuclei such as ${}^{12}\mathrm{N}$ can help inform and improve structure models.

Purpose: To learn about the decay of excited states in ${}^{12}\mathrm{N}$, to more generally inform nuclear structure models, particularly in the case of particle-unbound levels in low-mass systems which are within the reach of state-of-the-art ab initio calculations.

Method: In this follow-up analysis of previously published data [Chipps et al. (JENSA Collaboration), Phys. Rev. C 92, 034325 (2015)], decay particles from excited states populated in ${}^{12}\mathrm{N}$ have been detected in coincidence with tritons from the ${}^{14}\mathrm{N}(p,t){}^{12}\mathrm{N}$ transfer reaction. Specifically, decay protons from proton-unbound levels above $\sim 2$ MeV excitation energy were observed by utilizing the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target.

Results: Isotropic proton branching ratios for the $p0$ and $p1$ decay channels are calculated and decay particle spectra for the populated levels from $p0$, $p1$, and $p2$ decay are given.

Conclusions: The current data from ${}^{14}\mathrm{N}(p,t){}^{12}\mathrm{N}$ will help provide nuclear structure and decay information input to models in this mass region.

We show that correlated Gaussians with good angular momentum and parity provide flexible basis functions for specific elongated shape. As an application we study linear-chain states of four $\alpha$ particles in variation-after-projection calculations in which all the matrix elements are evaluated analytically. We find possible chain states for $J^{\pi }=0^{+},2^{+},4^{+}$ and perhaps $6^{+}$ with the bandhead energy being about 33 MeV from the ground state of ${}^{16}\mathrm{O}$. No chain states with $J\ge 8$ are found. The nature of the rotational sequence of the chain states is clarified in contrast to a rigid-body rotation. The quadrupole deformation parameters estimated from the chain states increase from 0.59 to 1.07 for $2^{+}$ to $6^{+}$. This work suggests undeveloped fields for the correlated Gaussians beyond those problems which have hitherto been solved successfully.

Lifetimes of the first excited $2^{+}$ states in the extremely neutron-deficient ${}^{162}\mathrm{W}$ and ${}^{164}\mathrm{W}$ nuclei have been measured using the recoil distance Doppler shift technique. Experimental $B\left(E2\right)$ data for the isotopic chains of hafnium, tungsten, and osmium, from the midshell region near the $\beta$-stability line towards the $N=82$ closed shell and the most neutron-deficient nuclides, are compared with predictions of nuclear deformations and ${2_1}^{+}\to {0_{\mathrm{g}.\mathrm{s}.}}^{+}$ reduced transition strengths from different classes of state-of-the-art theoretical model calculations. The results reveal striking differences and deficiencies in the predictive power of current nuclear structure models.

An exclusive measurement of the breakup of ${}^7\mathrm{Li}$ incident on a proton target was performed at 38.1 MeV (5.44 MeV/nucleon), probing the direct part of the excitation to the continuum. The two cluster constituents of ${}^7\mathrm{Li}$, ${}^4\mathrm{He}$, and ${}^3\mathrm{H}$, were recorded in coincidence in the MAGNEX spectrometer and a silicon detector respectively. Both detection systems were set at forward angles and the measurement of both kinematical solutions allowed the determination of a breakup angular distribution over a wide angular range in the center-of-mass frame. Comprehensive simulations provided the detection efficiency of the system and via the appropriate kinematics the transformation of the cross sections from the laboratory to the center-of-mass reference frame. The experimental results are analyzed and discussed together with previous elastic scattering data using the Continuum Discretized Coupled Channels (CDCC) framework and are found to be in satisfactory agreement. It was found that while the breakup cross section was dominated by the nonresonant component, the most important influence on the elastic scattering was due to coupling to the $7/2^{-}$ resonance of ${}^7\mathrm{Li}$.

The field of high-energy nuclear collisions has witnessed a surge of interest in the role played by hydrodynamic fluctuations. Hydrodynamic fluctuations may have significant effects on matter created in heavy-ion accelerators whose trajectories in the plane of temperature versus chemical potential pass near a possible critical endpoint. We extend previous studies to explore the impact of these fluctuations on Hanbury-Brown–Twiss interferometry of identical hadrons. With an appropriately defined correlation function we find that the fluctuations increase substantially when the trajectory passes near a critical endpoint and also displays a damped oscillatory behavior in the rapidity distance $\mathrm{\Delta }y$ unlike that originating from initial-state fluctuations.

We present a systematic procedure for analyzing cumulants to arbitrary order in the context of heavy-ion collisions. It generalizes and improves existing procedures in many respects. In particular, particles which are correlated are allowed to belong to different phase-space windows, which may overlap. It also allows for the analysis of cumulants at any order, using a simple algorithm rather than complicated expressions to be derived and coded by hand. In the case of azimuthal correlations, it automatically corrects to leading order for detector nonuniformity, and it is useful for numerous other applications as well. We discuss several of these applications: anisotropic flow, event-plane correlations, symmetric cumulants, and net baryon and net charge fluctuations.

Background: Combining the relativistic mean-field (RMF) model and distorted wave Born approximation (DWBA) method, Coulomb form factors for elastic electron scattering have been studied for several stable nuclei (${}^{208}\mathrm{Pb}, {}^{40}\mathrm{Ca}, {}^{32}\mathrm{S}$, and ${}^{24}\mathrm{Mg}$) with a methodology that can be extended to exotic nuclei.

Purpose: Previous studies on nuclear Coulomb form factors by the $\text{RMF}+\text{DWBA}$ method were mainly based on the spherical RMF model. This work aims to further extend the studies to the axially deformed RMF model.

Method: The nuclear proton density distributions are first calculated by the deformed RMF model. Next, the axially deformed density distributions are expanded into multipole components. With the spherical ${\rho }_0$ components, the Coulomb form factors of even-even nuclei are calculated by the DWBA method.

Results: For spherical nuclei, the nuclear Coulomb form factors obtained with the deformed RMF model almost coincide with those from the spherical RMF model. For deformed nuclei, Coulomb form factors obtained with the deformed RMF model agree better with the experimental data at the diffraction minima and at high momentum transfers.

Conclusions: Results indicate the proton densities calculated from the axially deformed RMF model are valid and reasonable. The electron-scattering experiments will soon be available for exotic nuclei, and the studies in this paper are helpful to interpret the experimental data of deformed exotic nuclei.

Detailed comparisons between the experimental data of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ at $95A$ MeV and transport model simulations are presented for all charged particles and fragments. For the simulations, antisymmetrized molecular dynamics (AMD), a modified version of AMD (AMD-FM), and constrained molecular dynamics (CoMD), are used. The experimental energy spectra and angular distributions are well reproduced by the AMD-FM calculations for light charged particles with $Z\le 2$. We show that the nuclear stopping plays a key role for these observables. The production mechanisms of light charged particles are discussed. The angular distributions of isotopes with $Z>2$ are qualitatively reproduced reasonably well, but the yields are $2–10$ times smaller in the simulations for most isotopes.

In this paper, I investigate the analytic properties of the quark propagator Dyson-Schwinger equation (DSE) in the Landau gauge. In the quark self-energy, the combined gluon propagator and quark-gluon vertex is modeled by an effective interaction (the so-called Maris-Tandy interaction), where the ultraviolet term is neglected. This renders the loop integrand of the quark self-energy analytic on the cut plane $-\pi <arg\left(x\right)<\pi$ of the square of the external momentum. Exploiting the simplicity of the truncation, I study solutions of the quark propagator in the domain $x\in [-5.1,0]{\text{GeV}}^2\times i[0,10.2]{\text{GeV}}^2$. Because of a complex conjugation symmetry, this region fully covers the parabolic integration domain for Bethe-Salpeter equations (BSEs) for bound state masses of up to 4.5 GeV. Employing a novel numerical technique that is based on highly parallel computation on graphics processing units (GPUs), I extract more than 6500 poles in this region, which arise as the bare quark mass is varied over a wide range of closely spaced values. The poles are grouped in 23 individual trajectories that capture the movement of the poles in the complex region as the bare mass is varied. The raw data of the pole locations and residues is provided as Supplemental Material, which can be used to parametrize solutions of the complex quark propagator for a wide range of bare mass values and for large bound-state masses. This study is a first step towards an extension of previous work on the analytic continuation of perturbative one-loop integrals, with the long-term goal of establishing a framework that allows for the numerical extraction of the analytic properties of the quark propagator with a truncation that extends beyond the rainbow by making adequate adjustments in the contour of the radial integration of the quark self-energy.

The nuclear level densities and $\gamma$-ray strength functions of ${}^{138,139,140}\mathrm{La}$ were measured using the ${}^{139}\mathrm{La}$(${}^3\mathrm{He},\alpha$), ${}^{139}\mathrm{La}$(${}^3\mathrm{He},\stackrel{\prime }{{}^3\mathrm{He}}$), and ${}^{139}\mathrm{La}$($d,p$) reactions. The particle-$\gamma$ coincidences were recorded with the silicon particle telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these experimental results, the low-energy enhancement in the $A\sim 140$ region is discussed. The ${}^{137,138,139}\mathrm{La}$($n,\gamma$) cross sections were calculated at $s$- and $p$-process temperatures using the experimentally measured nuclear level densities and $\gamma$-ray strength functions. Good agreement is found between ${}^{139}\mathrm{La}$($n,\gamma$) calculated cross sections and previous measurements.

Using published $E2$ matrix elements, I have determined the amount of mixing between the lowest two $2^{+},4^{+}$, and $6^{+}$ states in ${}^{72}\mathrm{Ge}$. I also extracted the $E2$ strengths connecting the unmixed states. One set of basis states is found to form an excellent $K=0$ rotational band, and the other is found to form a $K=2$ band.

Background: Core-excitation effects in the scattering of two-body halo nuclei have been investigated in previous works. In particular, these effects have been found to affect in a significant way the breakup cross sections of neutron-halo nuclei with a deformed core. To account for these effects, appropriate extensions of the continuum-discretized coupled-channels (CDCC) method have been recently proposed.

Purpose: We aim to extend these studies to the case of breakup reactions measured under complete kinematics or semi-inclusive reactions in which only the angular or energy distribution of one of the outgoing fragments is measured.

Method: We use the standard CDCC method as well as its extended version with core excitations, assuming a pseudostate basis for describing the projectile states. Two- and three-body observables are computed by projecting the discrete two-body breakup amplitudes, obtained within these reaction frameworks, onto two-body scattering states with definite relative momentum of the outgoing fragments and a definite state of the core nucleus.

Results: Our working example is the one-neutron halo ${}^{11}\mathrm{Be}$. Breakup reactions on protons and ${}^{64}\mathrm{Zn}$ targets are studied at 63.7 MeV/nucleon and 28.7 MeV, respectively. These energies, for which experimental data exist, and the targets provide two different scenarios where the angular and energy distributions of the fragments are computed. The importance of core dynamical effects is also compared for both cases.

Conclusions: The presented method provides a tool to compute double and triple differential cross sections for outgoing fragments following the breakup of a two-body projectile and might be useful to analyze breakup reactions with other deformed weakly bound nuclei, for which core excitations are expected to play a role. We have found that, while dynamical core excitations are important for the proton target at intermediate energies, they are very small for the Zn target at energies around the Coulomb barrier.

Background: The effect of core excitations in transfer reactions of the form $A(d,p)B$ has been reexamined by some recent works by using the Faddeev–Alt–Grassberger–Sandhas reaction formalism. The effect was found to affect significantly the calculated cross sections and to depend strongly and nonlinearly on the incident deuteron energy.

Purpose: Our goal is to investigate these effects within a coupled-channel formulation of the scattering problem which, in addition to being computationally less demanding than the Faddeev counterpart, may help shed some light onto the physical interpretation of the cited effects.

Method: We use an extended version of the continuum-discretized coupled-channel (CDCC) method with explicit inclusion of target excitations within a coupled-channel Born approximation (CDCC-BA) formulation of the transfer transition amplitude. We compare the calculated transfer cross sections with those obtained with an analogous calculation omitting the effect of target excitation. We consider also an adiabatic coupled-channel (ACC) method. Our working example is the ${}^{10}\mathrm{Be}(d,p){}^{11}\mathrm{Be}$ reaction.

Results: We find that the two considered methods (CDCC-BA and ACC) reproduce fairly well the reported energy dependence of the core excitation effect. The main deviation from the pure three-body model calculation (i.e., omitting core excitations) is found to mostly originate from the destructive interference of the direct one-step transfer and the two-step transfer following target excitation.

Conclusions: The proposed method; namely, the combination of the CDCC method and the CCBA formalism, provides a useful and accurate tool to analyze transfer reactions including explicitly, when needed, the effect of target excitations and projectile breakup. The method could be useful for other transfer reactions induced by weakly bound projectiles, including halo nuclei.

The pasta phases are calculated for warm stellar matter in a framework of relativistic mean-field models, including the possibility of light cluster formation. Results from three different semiclassical approaches are compared with a quantum statistical calculation. Light clusters are considered as point-like particles, and their abundances are determined from the minimization of the free energy. The couplings of the light clusters to mesons are determined from experimental chemical equilibrium constants and many-body quantum statistical calculations. The effect of these light clusters on the chemical potentials is also discussed. It is shown that, by including heavy clusters, light clusters are present up to larger nucleonic densities, although with smaller mass fractions.