We present calculations for symmetric nuclear matter using chiral nuclear interactions within the self-consistent Green's functions approach in the ladder approximation. Three-body forces are included via effective one-body and two-body interactions, computed from an uncorrelated average over a third particle. We discuss the effect of the three-body forces on the total energy, computed with an extended Galitskii-Migdal-Koltun sum-rule, as well as on single-particle properties. Saturation properties are substantially improved when three-body forces are included, but there is still some underlying dependence on the similarity renormalization group evolution scale.

The $\gamma p\to K^0{\Sigma }^{+}$ reaction has been measured from threshold to $E_{\gamma }=1.45$ GeV ($W_{\mathrm{CM}}=1.9$ GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the $3{\pi }^{0}p$ final state, by assuming $K_S^0\to {\pi }^0{\pi }^0$ and ${\Sigma }^{+}\to {\pi }^{0}p$. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve empirical knowledge about the $\gamma p\to K^0{\Sigma }^{+}$ reaction in the measured energy range. The results are compared to previous measurements and model predictions. It is demonstrated that adding the present $\gamma p\to K^0{\Sigma }^{+}$ results to existing data allowed a better description of this reaction with various models.

The nucleon resonances are investigated within a dynamical coupled-channels model of $\pi N$ and $\gamma N$ reactions up to the invariant mass $W=2$ GeV. The meson-baryon ($MB$) channels included in the calculations are $MB=$ $\pi N$, $\eta N$, $K\Lambda$, $K\Sigma$, and $\pi \pi N$ that has $\pi \Delta$, $\rho N$, and $\sigma N$ resonant components. The meson-baryon amplitudes $T_{M^{\prime }{B}^{\prime },MB}\left(W\right)$ are calculated from solving a set of coupled-channels integral equations defined by an interaction Hamiltonian consisting of (a) meson-exchange interactions $v_{M^{\prime }{B}^{\prime },MB}$ derived from phenomenological Lagrangian and (b) vertex interactions $N^{*}\to MB$ for describing the transition of a bare excited nucleon state $N^{*}$ to a meson-baryon channel $MB$.  The parameters of $v_{M^{\prime }{B}^{\prime },MB}$ are mainly constrained by the fit to the data of $\pi N\to \pi N$ in the low-energy region up to $W=1.4$ GeV. The bare masses of $N^{*}$ and the $N^{*}\to MB$ parameters are then determined in simultaneous fits to the data of $\pi N\to \pi N$ up to $W=2.3$ GeV and those of $\pi N\to \eta N,K\Lambda ,K\Sigma$ and $\gamma N\to \pi N,\eta N,K\Lambda ,K\Sigma$ up to $W=2.1$ GeV. The pole positions and residues of nucleon resonances are extracted by analytically continuing the meson-baryon amplitudes $T_{M^{\prime }{B}^{\prime },MB}\left(W\right)$ to the complex Riemann energy surface. From the extracted residues, we have determined the $N^{*}\to \pi N,\gamma N,\eta N,K\Lambda ,K\Sigma$ transition amplitudes at resonance poles. We compare the resonance pole positions from our analysis with those given by the Particle Data Group and the recent coupled-channels analyses by the Jülich and Bonn-Gatchina groups. Four results agree well only for the first $N^{*}$ in each spin-parity-isospin $(J^P,I)$ channel. For higher mass states, the number of states and their resonance positions from four results do not agree well. We discuss the possible sources of the discrepancies and the need of additional data from new hadron facilities such as the Japan Proton Accelerator Research Complex.

The operator structures that can contribute to three-nucleon forces are classified in the $1/N_c$ expansion. At leading order in $1/N_c$ a spin-flavor-independent term is present, as are the spin-flavor structures associated with the Fujita-Miyazawa three-nucleon force. Modern phenomenological three-nucleon forces are thus consistent with this $\mathcal{O}\left(N_c\right)$ leading force, corrections to which are suppressed by a power series in $1/N_c^2$. A complete basis of operators for the three-nucleon force, including all independent momentum structures, is given explicitly up to next-to-leading order in the $1/N_c$ expansion.

${}^{192}$Pt is produced solely by the slow neutron capture ($s$) nucleosynthesis process and hence an accurate ($n,\gamma$) reaction rate for this nuclide would allow its use as an important calibration point near the termination of the $s$-process nucleosynthesis flow. For this reason, we have measured neutron capture and total cross sections for ${}^{192,194,195,196,\mathrm{nat}}$Pt in the energy range from 10 eV to several hundred keV at the Oak Ridge Electron Linear Accelerator. Measurements on the other Pt isotopes were, in part, necessitated by the fact that only a relatively small ${}^{192}$Pt sample of modest enrichment was available. Astrophysical ${}^{192,194,195,196}$Pt($n,\gamma$) reaction rates, accurate to approximately 3%–5%, were calculated from these data. No accurate reaction rates have been published previously for any of these isotopes. At $s$-process temperatures, previously recommended rates are larger (by as much as 35%) and have significantly different shapes as functions of temperature than our new rates. We used our new Pt results, together with ${}^{191,193}$Ir($n,\gamma$) data, to calibrate nuclear statistical model calculations and hence obtain an improved rate for the unmeasured $s$-process branching-point isotope ${}^{192}$Ir.

Background: The pseudospin symmetry (PSS) has been studied extensively for bound states. Recently, we justified rigorously that the PSS in single-particle resonant states is exactly conserved when the attractive scalar and repulsive vector potentials of the Dirac Hamiltonian have the same magnitude but opposite sign [Phys. Rev. Lett. 109, 072501 (2012)].

Purpose: To understand more deeply the PSS in single-particle resonant states, we focus on several issues related to the exact conservation and breaking mechanism of the PSS in single-particle resonances. In particular, we are interested in how the energy and width splittings of PS partners depend on the depth of the scalar and vector potentials.

Methods: We investigate the asymptotic behaviors of radial Dirac wave functions. Spherical square-well potentials are employed in which the PSS breaking part in the Jost function can be well isolated. By examining the zeros of Jost functions corresponding to small components of the radial Dirac wave functions, general properties of the PSS are analyzed.

Results: By examining the Jost function, the occurrence of intruder orbitals is explained and it is possible to trace continuously the PS partners from the PSS limit to the case with a finite potential depth. The dependence of the PSS in resonances as well as in bound states on the potential depth is investigated systematically. We find a threshold effect in the energy splitting and an anomaly in the width splitting of pseudospin partners when the depth of the single-particle potential varies from zero to a finite value.

Conclusions: The conservation and the breaking of the PSS in resonant states and bound states share some similar properties. The appearance of intruder states can be explained by examining the zeros of Jost functions. Origins of the threshold effect in the energy splitting and the anomaly in the width splitting of PS partners, together with many other problems, are still open and should be further investigated.

We exactly solve the one-dimensional boost-invariant Boltzmann equation in the relaxation time approximation for arbitrary shear viscosity. The results are compared with the predictions of viscous and anisotropic hydrodynamics. Studying different nonequilibrium cases and comparing the exact kinetic-theory results to the second-order viscous hydrodynamics results we find that recent formulations of second-order viscous hydrodynamics agree better with the exact solution than the standard Israel-Stewart approach. Additionally, we find that, given the appropriate connection between the kinetic and anisotropic hydrodynamics relaxation times, anisotropic hydrodynamics provides a very good approximation to the exact relaxation time approximation solution.

The difference between the flow ellipticities of oppositely charged pions $\Delta v_2\equiv v_2\left[{\pi }^{-}\right]-v_2\left[{\pi }^{+}\right]$, measured recently by the STAR Collaboration at the Brookhaven National Laboratory Relativistic Heavy Ion Collider (RHIC) shows a linear dependence on the event charge asymmetry $A_{\pm }\equiv (N_{+}-N_{-})/(N_{+}+N_{-})\text{:}\Delta v_2\left(A_{\pm }\right)=\Delta v_2\left(0\right)+r{A}_{\pm }$ with a slope $r>0$ and a nonzero intercept $\Delta v_2\left(0\right)>0$ on the order of ${10}^{-4}$. We discuss two novel mechanisms, which could explain the nonzero value of the charged elliptic flow $\Delta v_2$ at zero charge asymmetry $A_{\pm }=0$, i.e., the nonzero positive intercept $\Delta v_2\left(0\right)$. Both effects are due to the electric fields created by the colliding ions. These fields have quadrupole asymmetry of the magnitude and the sign needed to account for the nonzero intercept $\Delta v_2\left(0\right)>0$ in the RHIC data. One of the mechanisms also involves the chiral magnetic effect. This mechanism, although negligible at RHIC energies, may become important at the CERN Large Hadron Collider energies.

The Airy structure of the nuclear rainbow and prerainbow in inelastic and elastic $\alpha +{}^{16}$O scattering is studied with the coupled channel method using a folding potential derived from the microscopic wave functions of ${}^{16}$O. The theoretical calculations reproduce the characteristic energy evolution of the Airy minimum of the experimental angular distributions. The energy levels with $\alpha$-cluster structure in ${}^{20}$Ne are reproduced well using the potentials determined from the analysis of scattering. It is shown that the emergence of the $K=0_3^{+}$ $\alpha$-cluster band with core excitation at 7.19 MeV in ${}^{20}$Ne is intimately related to the emergence of the prerainbow and rainbow in inelastic scattering to the ${}^{16}$O($0_2^{+}$). It is found that the $\alpha$-cluster states with core excitation, the prerainbow and the rainbow in inelastic scattering are understood in a unified way as well as in the case of elastic scattering.

We apply the successful Monte Carlo Glauber and IP-Glasma initial-state models of heavy-ion collisions to the much smaller size systems produced in proton-proton, proton-nucleus, and deuteron-nucleus collisions. We observe a significantly greater sensitivity of the initial-state geometry to details of multiparticle production in these models compared to nucleus-nucleus collisions. In particular, we find that the size of the system produced in $p+A$ collisions is very similar to the one produced in $p+p$ collisions and predict comparable Hanbury-Brown-Twiss radii in the absence of flow in both systems. Differences in the eccentricities computed in the models are large, while differences among the generated flow coefficients $v_2$ and $v_3$ are smaller. For a large number of participants in proton-lead collisions, the $v_2$ generated in the IP-Glasma model is comparable to the value obtained in proton-proton collisions. Viscous corrections to flow are large over characteristic lifetimes in the smaller size systems. In contrast, viscous contributions are significantly diminished over the longer space-time evolution of a heavy-ion collision.

Background: Obtaining reaction rates for nuclear astrophysics applications is often limited by the availability of radioactive beams. Indirect techniques to establish reaction rates often rely heavily on the properties of excited states inferred from mirror symmetry arguments. Mirror energy differences can depend sensitively on nuclear structure effects.

Purpose: The present work sets out to establish a detailed comparison of mirror symmetry in the $A=23$, $T=1/2$ mirror nuclei ${}^{23}$Na and ${}^{23}$Mg both to high spin, and high excitation energy, including beyond the proton threshold. These data can be used to benchmark state-of-the-art shell-model calculations of these nuclei.

Methods: Excited states in ${}^{23}$Na and ${}^{23}$Mg were populated using the ${}^{12}$C(${}^{12}$C,$p$) and ${}^{12}$C(${}^{12}$C,$n$) reactions at beam energies of 16 and 22 MeV, and their resulting $\gamma$ decay was measured with Gammasphere.

Results: Level schemes for ${}^{23}$Na and ${}^{23}$Mg have been considerably extended; highly excited structures have been found in ${}^{23}$Na, as well as their counterparts in ${}^{23}$Mg for previously known rotational structures in ${}^{23}$Na. Mirror symmetry has been investigated up to an excitation energy of 8 MeV and spin-parity of 13/2${}^{+}$. Excited states in the region above the proton threshold have been studied in both nuclei.

Conclusions: A detailed exploration of mirror symmetry has been performed which heavily constrains expectations as to how mirror energy differences should evolve for different structures. Agreement with shell-model calculations provides confidence in using such estimations where real data are absent.

An analysis of six different sets of experimental data indicates that infinite, neutron-proton symmetric, neutral nuclear matter has a critical temperature of $T_c=17.9\pm 0.4$ MeV, a critical density of ${\rho }_c=0.06\pm 0.01$ nucleons/fm${}^3$, and a critical pressure of $p_c=0.31\pm 0.07$ MeV/fm${}^3$. These values have been obtained by analyzing data from six different reactions studied in three experiments: two “compound nuclear” reactions, ${}^{58}\mathrm{Ni}{+}^{12}\mathrm{C}{\to }^{70}$Se and ${}^{64}\mathrm{Ni}{+}^{12}\mathrm{C}{\to }^{76}$Se (both performed at the LBNL 88-in. cyclotron); and four “multifragmentation” reactions, 1 GeV/$c$ $\pi {+}^{197}$Au (performed by the Indiana Silicon Sphere Collaboration), 1 GeV/nucleon ${}^{197}\mathrm{Au}{+}^{12}$C, 1 GeV/nucleon ${}^{139}\mathrm{La}{+}^{12}$C, and 1 GeV/nucleon ${}^{84}\mathrm{Kr}{+}^{12}$C (all performed by the Equation of State Collaboration). The charge yields of all reactions as a function of the excitation energy were fit with a version of Fisher's droplet model modified to account for the dual components of the fluid (i.e., protons and neutrons), Coulomb effects, finite-size effects, and angular momentum arising from the nuclear collisions.

Background: The triple-$\alpha$ reaction is the key to our understanding about the nucleosynthesis and the observed abundance of ${}^{12}$C in stars. The theory of this process is well established at high temperatures but rather ambiguous in the low temperature regime where measurements are impossible.

Purpose: Develop a new three-body method, which tackles properly the scattering boundary condition for three charged particles and takes into account both the resonant and the nonresonant reaction mechanisms on the same footing, to compute the triple-$\alpha$ reaction rate at low temperatures.

Methods: We combine the $R$-matrix expansion, the $R$-matrix propagation method, and the screening technique in the hyperspherical harmonics basis.

Results: Both the $2_1{}^{+}$ bound state and the $0_2{}^{+}$ resonant state in ${}^{12}$C are well reproduced. We also study the cluster structure of these states. We calculate the triple-$\alpha$ reaction rate for $T=0.01–0.1$ GK.

Conclusions: We obtain the same rate as NACRE for temperatures above $0.07$ GK, but the new rate is largely enhanced at lower temperatures ($\approx$${10}^{12}$ at $0.02$ GK). The differences are caused by the direct capture contribution to the reaction when three $\alpha$ particles cannot reach the resonant energies.

Production cross sections for neutron-rich nuclei from the fragmentation of a ${}^{82}$Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 126 neutron-rich isotopes of elements $11\le Z\le 32$ were scanned using an experimental approach of varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements $22\le Z\le 25$ (${}^{64}$Ti, ${}^{67}$V, ${}^{69}$Cr, and ${}^{72}$Mn). One event was registered consistent with ${}^{70}$Cr and another one with ${}^{75}$Fe. The production cross sections are correlated with $Q_g$ systematics to reveal trends in the data. The results presented here confirm our previous results from a similar measurement using a ${}^{76}$Ge beam and can be explained with a shell model that predicts a subshell closure at $N=34$ around $Z=20$. This is demonstrated by systematic trends and calculations with the abrasion-ablation model that are sensitive to separation energies.

We study the equation of state and composition of hypernuclear matter within a relativistic density functional theory with density-dependent couplings. The parameter space of hyperon–scalar-meson couplings is explored by allowing for mixing and breaking of SU(6) symmetry, while keeping the nucleonic coupling constants fixed. The subset of equations of state, which corresponds to small values of hyperon–scalar-meson couplings, allows for massive $M\le 2.25M_{\odot }$ compact stars; the radii of hypernuclear stars are within the range 12–14 km. We also study the equation of state of hot neutrino-rich and neutrinoless hypernuclear matter and confirm that neutrinos stiffen the equation of state and dramatically change the composition of matter by keeping the fractions of charged leptons nearly independent of the density prior to the onset of neutrino transparency. We provide piecewise polytropic fits to six representative equations of state of hypernuclear matter, which are suitable for applications in numerical astrophysics.

The controlled transfer of nuclear state population using two x-ray laser pulses is investigated theoretically. The laser pulses drive two nuclear transitions in a nuclear three-level system facilitating coherent population transfer via the quantum optics technique of stimulated Raman adiabatic passage. To overcome present limitations of the x-ray laser frequency, we envisage accelerated nuclei interacting with two copropagating or crossed x-ray laser pulses in a three-beam setup. We present a systematic study of this setup providing both pulse temporal sequence and laser pulse intensity for optimized control of the nuclear state population. The tolerance for geometrical parameters such as laser beam divergence of the three-beam setup as well as for the velocity spread of the nuclear beam are studied and a two-photon resonance condition to account for experimental uncertainties is deduced. This additional condition gives a less strict requirement for the experimental implementation of the three-beam setup. Present experimental state of the art and future prospects are discussed.

Excited states of ${}^{76}$Ge have been populated in above-barrier Coulomb excitation and inelastic scattering of a 530-MeV ${}^{76}$Ge beam on a ${}^{238}$U target and studied using in-beam $\gamma$-ray spectroscopy with the Gammasphere array. The $\gamma$ band was extended considerably and one new band was identified. Comparisons of the $\gamma$ band with collective- and shell-model calculations suggest that ${}^{76}$Ge may be a rare example of a nucleus exhibiting rigid triaxial deformation in the low-lying states.

Background: The calculation of the hyperon binding energy in hypernuclei is crucial to understanding the interaction between hyperons and nucleons.

Purpose: We assess the relative importance of two- and three-body hyperon-nucleon force by studying the effect of the hyperon-nucleon-nucleon interaction in closed shell $\Lambda$ hypernuclei from A = 5 to 91.

Methods: The $\Lambda$ binding energy has been calculated using the auxiliary field diffusion Monte Carlo method for the first time, to study light and heavy hypernuclei within the same model.

Results: Our results show that including a three-body component in the hyperon-nucleon interaction leads to a saturation of the $\Lambda$ binding energy remarkably close to the experimental data. In contrast, the two-body force alone gives an unphysical limit for the binding energy.

Conclusions: The repulsive contribution of the three-body hyperon-nucleon-nucleon force is essential to reproduce, even qualitatively, the binding energy of hypernuclei in the mass range considered.

We find the height of the third fission barrier $B_{\mathrm{III}}$ and energy of the third minimum $E_{\mathrm{III}}$ in ${}^{232}$Th using the macroscopic-microscopic model, which is very well tested in this region of nuclei. For the first time it is done on an eight-dimensional deformation hypercube. The dipole distortion is included among the shape variables to ensure that no important shapes are missed. The saddle point is found on a lattice containing more than $50\times {10}^6$ points by the immersion water flow method. The shallow third minimum, $B_{\mathrm{III}}-E_{\mathrm{III}}\approx 0.36$ MeV, agrees with the experimental data of Blons et al. [Phys. Rev. Lett. 35, 1749 (1975)]. This is in sharp contrast with the status of the third minima in ${}^{232-236}$U: their experimental depth of $\ge 3$ MeV contradicts all realistic theoretical predictions. We emphasize the importance of repeating the experiment on ${}^{232}$Th, by a technique similar to that used in the uranium nuclei, for settling the puzzle of the third minima in actinides.

We introduce a unified approach to nuclear bound and continuum states based on the coupling of the no-core shell model (NCSM), a bound-state technique, with the no-core shell model/resonating group method (NCSM/RGM), a nuclear scattering technique. This new ab initio method, no-core shell model with continuum (NCSMC), leads to convergence properties superior to either NCSM or NCSM/RGM while providing a balanced approach to different classes of states. In the NCSMC, the ansatz for the many-nucleon wave function includes (i) a square-integrable $A$-nucleon component expanded in a complete harmonic oscillator basis and (ii) a binary-cluster component with asymptotic boundary conditions that can properly describe weakly bound states, resonances, and scattering. The Schrödinger equation is transformed into a system of coupled-channel integral-differential equations that we solve using a modified microscopic $R$-matrix formalism within a Lagrange mesh basis. We demonstrate the usefulness of the approach by investigating the unbound ${}^7$He nucleus.