We extend the self-consistent Green's functions formalism to take into account three-body interactions. We analyze the perturbative expansion in terms of Feynman diagrams and define effective one- and two-body interactions, which allows for a substantial reduction of the number of diagrams. The procedure can be taken as a generalization of the normal ordering of the Hamiltonian to fully correlated density matrices. We give examples up to third order in perturbation theory. To define nonperturbative approximations, we extend the equation-of-motion method in the presence of three-body interactions. We propose schemes that can provide nonperturbative resummation of three-body interactions. We also discuss two different extensions of the Koltun sum rule to compute the ground state of a many-body system.

The universality of the critical-temperature-included fluctuation model (CTFM) in explaining the evolution of the giant dipole resonance (GDR) width as a function of angular momentum is examined in light of recent experimental data on ${}^{144}$Sm and ${}^{152}$Gd. We compare both data sets with the phenomenological formula based on the CTFM and the thermal shape fluctuation model (pTSFM). The CTFM describes both data sets reasonably well using the actual ground state GDR width (${\Gamma }_0$), whereas the pTSFM describes the ${}^{144}$Sm data well but is unable to explain the ${}^{152}$Gd data using a single value of ${\Gamma }_0$ for the two excitation energies. These interesting results clearly indicate that the phenomenological CTFM can be used universally to describe the evolution of the GDR width with both angular momentum and temperature in the entire mass region. Moreover, it should provide insights into the modification of the TSFM.

Recent ground-state-focused studies of the tensor effects in the mean-field framework are our starting point. On the basis of phenomenological arguments, we indicate regions for acceptable values of the parameters that are associated with the tensor effective forces within both the Skyrme and the Gogny models. We identify acceptable signs and values of the parameters by making an adjustment on the neutron $1f$ spin-orbit splitting for the nuclei ${}^{40}$Ca, ${}^{48}$Ca, and ${}^{56}$Ni. The first nucleus is not used to adjust the tensor parameters because it is spin-saturated, but is employed to tune the spin-orbit strength. One of the main conclusions of this work is that some existing Skyrme parametrizations containing the tensor force should not be employed because the wrong sign of the tensor parameters does not lead to the correct behavior (by comparing with the experimental results). This study also allows us to better constrain the tensor parameters in the Gogny case, where much less work is published and boundaries and signs for the parameters have not been analyzed so far.

High-energy-resolution ${}^{56}$Fe(${}^3\mathrm{He},t$)${}^{56}$Co reaction measurements were performed at forward angles including $0^{\circ }$. From the spectra obtained, the splitting of the Fermi transition strength and thus the isospin mixing between the $J^{\pi }=0^{+}$ isobaric analog state (IAS) at 3.60 MeV and a neighboring $0^{+}$ state at 3.53 MeV have been investigated. In order to distinguish between states excited in Fermi and Gamow-Teller (GT) transitions, the measurements were performed at two ${}^3$He beam energies of 140 and 100 MeV/nucleon. Owing to the different incident energy dependencies of the $\sigma \tau$- and $\tau$-type effective interaction strengths, it is expected that the Fermi transitions are stronger relative to GT transitions at lower beam energies. Therefore the excitation of a state by the Fermi transition could be identified by the $\Delta L=0$ angular distribution and the ratio of transition strengths at these two incident energies. In the energy region around the IAS at 3.60 MeV, it was found that the state at 3.53 MeV is also excited by the Fermi transition and thus it has $J^{\pi }$ values of $0^{+}$. A value of 32.3(5) keV could be deduced for the off-diagonal matrix element of the Hamiltonian that causes the isospin mixing. A corresponding isospin impurity of $28\pm 1$% was obtained.

We present a method for solving the nucleon-nucleon scattering equation without the use of a partial wave expansion of the scattering amplitude. After verifying the accuracy of the numerical solutions, we proceed to apply the method to the in-medium scattering equation (the Bethe-Goldstone equation) in three dimensions. A focal point is a study of Pauli blocking effects calculated in the (angle-dependent) three-dimensional formalism as compared to the usual spherical approximation. We discuss our results and their implications.

The contribution of various components of potential towards balance energy is analyzed for the reactions of ${}_{26}^{58}\text{Fe}+{}_{26}^{58}\text{Fe}$, ${}_{28}^{58}\text{Ni}+{}_{28}^{58}\text{Ni}$, ${}_{36}^{86}\text{Kr}+{}_{41}^{93}\text{Nb}$, and ${}_{79}^{197}\text{Au}+{}_{79}^{197}\text{Au}$ using an isospin-dependent quantum molecular dynamics (IQMD) model. We show that the balance energy changes with the addition of various components of potentials. Our calculations for the considered energy range clearly demonstrate the dominance of the Coulomb potential and momentum-dependent interactions over the other potentials for the lighter colliding systems. However, the contribution of the symmetry potential also becomes significant while handling heavier nuclei.

Conventional coupled-channels analyses, that take account of only the collective excitations of the colliding nuclei, have failed to reproduce the different behavior of the experimental quasi-elastic barrier distributions for the ${}^{20}$Ne+${}^{90,92}$Zr systems. To clarify the origins of this difference, we investigate the effect of noncollective excitations of the Zr isotopes. Describing these excitations in a random-matrix model, we explicitly take them into account in our coupled-channels calculations. The noncollective excitations are capable of reproducing the observed smearing of the peak structure in the barrier distribution for ${}^{20}$Ne+${}^{92}$Zr, while not significantly altering the structure observed in the ${}^{20}$Ne+${}^{90}$Zr system. The difference is essentially related to the closed neutron shell in ${}^{90}$Zr.

We extend the ab initio no-core shell model/resonating-group method to include three-nucleon ($3N$) interactions for the description of nucleon-nucleus collisions. We outline the formalism, give algebraic expressions for the $3N$-force integration kernels, and discuss computational aspects of two alternative implementations. The extended theoretical framework is then applied to nucleon-${}^4$He elastic scattering using similarity-renormalization-group (SRG)-evolved nucleon-nucleon plus $3N$ potentials derived from chiral effective field theory. We analyze the convergence properties of the calculated phase shifts and explore their dependence upon the SRG evolution parameter. We include up to six excited states of the ${}^4\text{He}$ target and find significant effects from the inclusion of the chiral $3N$ force, e.g., it enhances the spin-orbit splitting between the $3/2^{-}$and $1/2^{-}$ resonances and leads to an improved agreement with the phase shifts obtained from an accurate $R$-matrix analysis of the five-nucleon experimental data. We find remarkably good agreement with measured differential cross sections at various energies below the $d$-${}^3$H threshold, while analyzing powers manifest larger deviations from experiment for certain energies and angles.

By using simple direct-reaction models, I have estimated the ratio of excited 0${}^{+}$ to ground-state production in ${}^{10}$He for several different reactions. I present the results as a function of the amount of mixing between the two basis states.

Proton-unbound excited states of ${}^{31}$S have been populated with the ${}^{32}$S($d,t$)${}^{31}$S reaction at a beam energy of 24 MeV. Tritons corresponding to ${}^{31}$S states with $E_x{(}^{31}S)\approx 6.3$–$7.1$ MeV were momentum analyzed with a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph at six angles ranging from ${\theta }_{\mathrm{lab}}={15}^{\circ }$ to $58.5^{\circ }$. We report a statistically significant detection of an astrophysically important state at $E_x{(}^{31}S)=6402$ (2) keV, whose existence as a third state in this region has been under debate. Using updated $A=31$ nuclear structure information, we present a new set of proposed ${}^{31}$S-${}^{31}$P mirror assignments for ${}^{31}$S, in which this state is tentatively assigned a spin of 7/2. This level, corresponding to a ${}^{30}$P + $p$ resonance at 271 keV, is likely to have a significant influence on the ${}^{30}$P($p,\gamma$)${}^{31}$S reaction rate in explosive hydrogen burning in classical novae.

The covariant density functional theory with the point-coupling density functional PC-PK1 and the meson-exchange density functional PK1 has been applied to study the intrinsic triaxial and octupole deformation for ${}^{293,294}$117 isotopes, and the $Q_{\alpha }$ values of their $\alpha$-decay chains. The shape coexistence of normal deformation and prolate superdeformation is found in ${}^{293,294}$117 and some of their successive decay products. The $Q_{\alpha }$ data of the $\alpha$-decay chains are well reproduced. In particular, the influences of shape coexistence and rotational correction are examined.

Exclusive measurements of the quasifree $pn\to pp{\pi }^0{\pi }^{-}$ reaction have been performed by means of $pd$ collisions at $T_p$ $=$ 1.2 GeV using the wide angle shower apparatus (WASA) detector setup at the cooler synchrotron COSY (Institut für Kernphysik, Jülich). Total and differential cross sections have been obtained covering the energy region $\sqrt{s}$ $=$ (2.35–2.46) GeV, which includes the region of the ABC effect and its associated resonance structure. No ABC effect, i.e., low-mass enhancement is found in the ${\pi }^0{\pi }^{-}$-invariant mass spectrum, in agreement with the constraint from Bose statistics that the isovector pion pair can not be in relative $s$ wave. At the upper end of the covered energy region $t$-channel processes for Roper, $\Delta \left(1600\right)$ and $\Delta \Delta$ excitations provide a reasonable description of the data, but at low energies the measured cross sections are much larger than predicted by such processes. Adding a resonance amplitude for the resonance at $m$ $=$ 2.37 GeV with $\Gamma$ $=$ 70 MeV and $I\left(J^P\right)=0\left(3^{+}\right)$ observed recently in $pn\to d{\pi }^0{\pi }^0$ and $pn\to d{\pi }^{+}{\pi }^{-}$ reactions leads to an agreement with the data also at low energies.

In this paper, an off-shell extrapolation is proposed for the Regge-model $\mathit{NN}$ amplitudes presented in a paper by Ford and Van Orden [Phys. Rev. C 87, 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). A prescription for extrapolating these amplitudes for one nucleon off-shell in the initial state is given. Application of these amplitudes to calculations of deuteron electrodisintegration is presented and compared to the limited available precision data in the kinematical region covered by the Regge model.

Excited states of ${}^{195}$At have been studied by means of in-beam $\gamma$-ray spectroscopy and the recoil-decay tagging technique. A strongly coupled rotational band feeding the $\alpha$-decaying $7/2^{-}$ state via unobserved transitions was identified. This band is presumably built on the oblate proton $I^{\pi }=13/2^{+}$ state. Confirming earlier measurements, $\alpha$ decays from the $1/2^{+}$ and $7/2^{-}$ states were observed. Additionally, an $E3$ branch competing with the $\alpha$ decay of the $7/2^{-}$ state was inferred. Also $\alpha$ decays of the odd-odd isotopes ${}^{194,196}$At were examined.

Parity-violating electron scattering (PVS) is an accurate and model-independent way to investigate the weak-charge density distributions of nuclei. In this paper, we study parity-violating electron scattering with the Helm model where the effects of spin-orbit currents on nuclear weak skins are taken into account. The conditions of two PVS measurements to constrain the surface thickness ${\sigma }_W$ of Helm weak-charge densities are investigated. According to the plane wave Born approximation, $A_{\mathrm{pv}}$ is expressed in terms of parameters of the corresponding Helm charge and weak-charge densities. After fitting the results of $A_{\mathrm{pv}}$ calculated from the phase-shift analysis method where the Coulomb distortion effects are incorporated, an empirical formula in terms of Helm model parameters for calculating $A_{\mathrm{pv}}$ is obtained. If two PVS measurements with different scattering angles are carried out, the modeled weak-charge density distributions with two parameters could be extracted from this empirical formula.

The mass surface in the $A\sim 100$ region of the nuclear chart is extended by the measurement of the ${}^{98–100}$Rb isotopes with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The mass of ${}^{100}$Rb is determined for the first time. The studied nuclides mark the known low-$Z$ frontier of the shape transition at $N=60$. To describe the shape evolution towards the krypton isotopic chain, a theoretical analysis is presented in the framework of the Hartree-Fock-Bogoliubov approach. The importance of the pairing interaction for describing the extent and strength of the region of quadrupole deformation is emphasized. A later transition to large prolate deformation or, alternatively, the predominance of oblate deformation is proposed as explanation for the different behavior of the krypton isotopes. Octupole collectivity is explored as a possible mechanism for the evolution of two-neutron separation energies around $N=56$.

We described the nuclear excitation by electron transition (NEET) by using strict collision theory combined with quantum electrodynamics. All stages of the process are considered, which include ionization of the atom by an x-ray photon with the formation of the hole in an inner electronic shell, its decay accompanied by the excitation of the nucleus, and the subsequent deexcitation of the nucleus. The cross sections for the NEET and photoabsorption of x rays are calculated near the threshold. We also analyzed the fine structure of the NEET curve analogous to the extended x-ray-absorption fine structure, well known in x-ray optics. The results agree with the findings of Kishimoto et al. [Phys. Rev. C 74, 031301(R) (2006)].

The recent measured values of the fusion excitation functions of the heavy-ion colliding systems ${}^{28}$Si${+}^{100}$Mo, ${}^{58}$Ni${+}^{54}$Fe, and ${}^{64}$Ni${+}^{64}$Ni are investigated using the original version of the proximity formalism. The fusion cross sections are calculated based on the coupled-channels approach, including couplings to the low-lying $2^{+}$ and $3^{-}$ states in both target and projectile nuclei. The comparison between the calculated and the measured values of the fusion excitation functions indicates that the potential Prox.77 needs to be modified considerably at sub-barrier energies. In the present study, the role of the surface energy coefficient $\gamma$ and also the temperature $T$ of the compound nucleus in nuclear potential and fusion cross section has been explored for our colliding systems. Moreover, the mutual and the multiphonon excitations of the lowest $2^{+}$ and $3^{-}$ states are considered in the coupled-channels calculations. It is demonstrated that the potential Prox.77 with these corrective effects can reproduce the experimental data of the fusion cross section, the $S$ factor and the logarithmic derivative for fusion reactions ${}^{28}$Si${+}^{100}$Mo, ${}^{58}$Ni${+}^{54}$Fe, and ${}^{64}$Ni${+}^{64}$Ni with good accuracy especially at below-barrier energies.

Background: The formation of superheavy elements by fusion of two massive nuclei is severely inhibited by the competing quasifission process.

Purpose: Through extensive mass-angle distribution measurements, we map out the systematic dependence of quasifission characteristics as a function of the identity of the colliding nuclei.

Methods: The Australian National University's Heavy Ion Accelerator Facility and CUBE spectrometer have been used to measure mass-angle distributions for 42 reactions forming heavy elements. Beam energies above their respective capture barriers were used to minimize the known influence of nuclear structure effects.

Results: Different mappings of mass-angle distribution characteristics (including timescales) over the nuclear landscape show a systematic dependence on entrance channel and compound nucleus fissilities.

Conclusions: The results provide an empirical baseline to assess effects of nuclear structure at lower beam energies, and motivate the testing and validation of complete dynamical models of heavy element fusion through comparison of mass-angle distributions.

Recently we presented a successful strategy to extract the position of the two $\Lambda \left(1405\right)$ poles from experimental photoproduction data on the $\gamma p\to K^{+}{\pi }^0{\Sigma }^0$ reaction at Jefferson Lab. Following a similar strategy, we extend the previous method to incorporate also the isospin 1 component which allows us to consider in addition the experimental data on $\gamma p\to K^{+}{\pi }^{\pm }{\Sigma }^{\mp }$. The idea is based on considering a production mechanism as model independent as possible and implementing the final state interaction of the final meson-baryon pair based on small modifications of the unitary chiral perturbation theory amplitudes. Good fits to the data are obtained with this procedure, by means of which we can also predict the cross sections for the $K^{-}p\to \overline{K}N$, $\pi \Sigma$, and $\pi \Lambda$ reactions for the different charge channels. Besides the two poles found for the $\Lambda \left(1405\right)$ resonance, we discuss the possible existence of an isospin 1 resonance in the vicinity of the $\overline{K}N$ threshold.