A $\gamma \gamma$ angular-correlation experiment has been performed to investigate the low-energy states of the nucleus ${}^{98}$Mo. The new data, including spin assignments, multipole mixing ratios, and lifetimes reveal evidence for shape coexistence and mixing in ${}^{98}$Mo, arising from a proton intruder configuration. This result is reproduced by a theoretical calculation within the proton-neutron interacting boson model with configuration mixing, based on microscopic energy density functional theory. The microscopic calculation indicates the importance of the proton particle-hole excitation across the $Z=40$ subshell closure and the subsequent mixing between spherical vibrational and the $\gamma$-soft equilibrium shapes in ${}^{98}$Mo.

The low-energy structure of ${}^{65}$Fe has been studied by means of $\gamma$ and fast-timing spectroscopy at the ISOLDE facility, CERN. A level scheme of ${}^{65}$Fe populated following the ${\beta }^{-}$decay of ${}^{65}$Mn was established for the first time. It includes 41 levels and 85 transitions. The excitation energy of the $\beta$-decaying isomer in ${}^{65}$Fe has been precisely determined at 393.7(2) keV. The $\beta$-delayed neutron emission branch was measured as $P_n$ $=$ 7.9(12)$\%$, which cannot be reconciled with the previously reported value of 21.0(5)$\%$. Four $\gamma$ rays and four excited states in ${}^{64}$Fe were identified as being populated following the $\beta$-$n$ decay. Four lifetimes and five lifetime limits in the subnanosecond range have been measured using the advanced time-delayed $\beta \gamma \gamma \left(t\right)$ method. The level scheme is compared with shell-model calculations. Tentative spin and parity assignments are proposed based on the observed transition rates, the calculations, and the systematics of the region.

We study energy landscapes for selected superheavy even-even systems with $Z=128–148$ using both the microscopic-macroscopic Woods-Saxon and Skyrme SLy6 Hartree-Fock plus BCS models. Including nonaxial shapes proves crucial, as many apparent minima obtained when studying only axially symmetric shapes turn out to be saddle points, and triaxiality can drastically reduce fission barriers. Although both models often predict similar equilibria, only the SLy6 model predicts moderate stability in the $N\gtrsim 228$ region, with barriers up to 4.5 MeV. A rough estimate suggests fission half-lives in the $\mu$s range; this would mean $\sim$ms halflives of odd and odd-odd systems. Nuclei from the $N\approx 180$ region with predicted $\approx$4 MeV fission barriers have short $\alpha$ half-lives. There is no sign of stability for intermediate neutron numbers. As the SLy6 interaction is known to overestimate fission barriers, no long-lived nuclei are to be expected in the whole studied region. The shell corrections obtained in two models suggest a probable doubly magic system $Z=164$, $N=308$, with the half-life of 100 s estimated in the Woods-Saxon model.

We report the exclusive photoproduction cross sections for the ${\Sigma }^0\left(1385\right)$, $\Lambda \left(1405\right)$, and $\Lambda \left(1520\right)$ in the reactions $\gamma +p\to K^{+}+Y^{*}$ using the CLAS detector for energies from near the respective production thresholds up to a center-of-mass energy $W$ of $2.85$ GeV. The differential cross sections are integrated to give the total exclusive cross sections for each hyperon. Comparisons are made to current theoretical models based on the effective-Lagrangian approach and fit to previous data. The accuracy of these models is seen to vary widely. The cross sections for the $\Lambda \left(1405\right)$ region are strikingly different for the ${\Sigma }^{+}{\pi }^{-}$, ${\Sigma }^0{\pi }^0$, and ${\Sigma }^{-}{\pi }^{+}$ decay channels, indicating the effect of isospin interference, especially at $W$ values close to the threshold.

Latest generation fission experiments provide an excellent testing ground for theoretical models. In this contribution we compare the measurements for ${}^{235}$U($n_{\mathrm{th}}$,f), obtained with the Detector for Advanced Neutron Capture Experiments (DANCE) calorimeter at Los Alamos Neutron Science Center (LANSCE), with our full-scale simulation of the primary fragment de-excitation, using the recently developed cgmf code, based on a Monte Carlo implementation of the Hauser-Feshbach theoretical model. We compute the isomer ratios as a function of the initial angular momentum of the fission fragments, for which no direct information exists. Comparison with the available experimental data allows us to determine the initial spin distribution. We also study the dependence of the isomer ratio on the knowledge of the low-lying discrete spectrum input for nuclear fission reactions, finding a high degree of sensitivity. Finally, in the same Hauser-Feshbach approach, we calculate the isomer production ratio for thermal neutron capture on stable isotopes, where the initial conditions (spin, excitation energy, etc.) are well understood. We find that with the current parameters involved in Hauser-Feshbach calculations, we obtain up to a factor of 2 deviation from the measured isomer ratios.

We introduce a new technique to calculate perturbative corrections to neutron-deuteron ($nd$) scattering that does not require calculation of the full off-shell scattering amplitude. Its relation to the more familiar partial-resummation technique is explained. Also included is a calculation of the SD-mixing term that occurs at next-to-next-to-leading-order (NNLO) in pionless effective field theory (${\mathrm{EFT}}_{\neg \pi }$). By using the new technique with the SD-mixing term, a complete strictly perturbative phase-shift analysis of $nd$ scattering is performed up to NNLO including eigenphases and mixing angles. This is compared to potential model calculations and good agreement is found with the eigenphases and some of the mixing angles at low energies.

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.

A new microscopic theory for nuclear pairing is proposed through the generalized density matrix formalism. Instead of the variation principle, we start from the Heisenberg equations of motion for density matrix operators $K_{12}\equiv a_2{a}_1$. The theory generalizes the well-known particle-particle random-phase approximation. Its analytical equations are as simple as that of the BCS theory and can be solved within a similar computer time if the model space is not too large. The current theory conserves the exact particle number and is valid at arbitrary pairing strength (including those below the BCS critical strength). It is also of interest to other mesoscopic systems such as ultrasmall metallic grains.

We propose a finite dimensional representation for the potential operator such that it retains some information about the whole Hilbert-space representation. The potential should be represented in a larger basis, then the matrix should be inverted, then truncated to the desired size, and finally inverted again. This procedure results in a superb low-rank representation of the potential operator.

The half-life of the yrast $I^{\pi }=2^{+}$ state in the neutron-rich nucleus ${}^{188}$W has been measured using fast-timing techniques with the HPGe and LaBr${}_3$:Ce array at the National Institute of Physics and Nuclear Engineering, Bucharest. The resulting value of $t_{1/2}=0.87\left(12\right)$ ns is equivalent to a reduced transition probability of $B(E2;2_1^{+}\to 0_1^{+})=85\left(12\right)$ W.u. for this transition. The $B(E2;2_1^{+}\to 0_1^{+})$ is compared to neighboring tungsten isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES) calculations have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly increasing $\gamma$ softness for ${}^{184–192}$W and an oblate minimum for ${}^{194}$W.

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.

Recently a new observable to study halo nuclei was introduced, based on the ratio between breakup and elastic angular cross sections. This new observable is shown by the analysis of specific reactions to be independent of the reaction mechanism and to provide nuclear structure information of the projectile. Here we explore the details of this ratio method, including the sensitivity to binding energy and angular momentum of the projectile. We also study the reliability of the method with breakup energy. Finally, we provide guidelines and specific examples for experimentalists who wish to apply this method.

We model the initial confinement-deconfinement transition in relativistic heavy-ion collisions as a rapid quench in view of expected rapid thermalization to a quark-gluon plasma state. The transition is studied using the Polyakov loop model, with the initial field configuration (in the confining phase) covering a small neighborhood of the confining vacuum $l\simeq 0$, as appropriate for $T<T_c$. Quench is implemented by evolving this initial configuration with the effective potential at a temperature $T>T_c$. We study the formation of $Z\left(3\right)$ domain structure and its evolution during the transition as $l$ rolls down in different directions from the top of the central hill in the effective potential of $l$. When explicit $Z\left(3\right)$ symmetry-breaking effects (arising from dynamical quark effects) are small, then we find well defined $Z\left(3\right)$ domains, which coarsen in time. Remarkably, the magnitude plot of $l$ shows vacuum bubblelike configurations arising during the quench. This first-order transitionlike behavior occurs even though there is no metastable vacuum separated by a barrier from the true vacuum for the parameter values used. When the initial field configuration everywhere rolls down roughly along the same direction (as will happen with large explicit symmetry breaking) then we do not find such bubblelike configurations. However, in this case we find huge oscillations of $l$ with large length scales. We show that such large oscillations can lead to large fluctuations in the evolution of flow anisotropies compared to the equilibrium transition case.

The suppression of heavy quarkonia, e.g., $J/\psi$, ${\rm Y}$, etc., is considered as a suitable probe to identify the nature of the matter created in heavy ion collisions. Recently we have presented a modified color screening model for $J/\psi$ suppression in the quark gluon plasma (QGP) using a quasiparticle model as the equation of state. In this paper, we extend our model to calculate the anomalous suppression of various states of ${\rm Y}$ arising due to QGP medium alone. We obtain the suppression patterns of the different bottomonia states with respect to centrality at various available collision energies and compare them with the available experimental data.

The Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet were used to measure the free neutrons and heavy charged particles from the radioactive ion beam induced ${}^{32}$Mg+${}^9$Be reaction. The fragmentation reaction was simulated with the constrained molecular dynamics model (CoMD), which demonstrated that the $\langle N/Z\rangle$ of the heavy fragments and free neutron multiplicities were observables sensitive to the density dependence of the symmetry energy at subsaturation densities. Through comparison of these simulations with the experimental data, constraints on the density dependence of the symmetry energy were extracted. The advantage of radioactive ion beams as a probe of the symmetry energy is demonstrated through examination of CoMD calculations for stable and radioactive-beam-induced reactions.

A high-precision branching-ratio measurement for the superallowed ${\beta }^{+}$ decay of ${}^{74}$Rb was performed at the TRIUMF Isotope Separator and Accelerator (ISAC) radioactive ion-beam facility. The scintillating electron-positron tagging array (SCEPTAR), composed of 10 thin plastic scintillators, was used to detect the emitted $\beta$ particles; the 8$\pi$ spectrometer, an array of 20 Compton-suppressed HPGe detectors, was used for detecting $\gamma$ rays that were emitted following Gamow-Teller and nonanalog Fermi ${\beta }^{+}$ decays of ${}^{74}$Rb; and the Pentagonal Array of Conversion Electron Spectrometers (PACES), an array of 5 Si(Li) detectors, was employed for measuring $\beta$-delayed conversion electrons. Twenty-three excited states were identified in ${}^{74}$Kr following $8.241\left(4\right)\times {10}^8$ detected ${}^{74}$Rb $\beta$ decays. A total of 58 $\gamma$-ray and electron transitions were placed in the decay scheme, allowing the superallowed branching ratio to be determined as $B_0=99.545\left(31\right)\%$. Combined with previous half-life and $Q$-value measurements, the superallowed branching ratio measured in this work leads to a superallowed $ft$ value of 3082.8(65) s. Comparisons between this superallowed $ft$ value and the world-average-corrected $\overline{\mathcal{F}t}$ value, as well as the nonanalog Fermi branching ratios determined in this work, provide guidance for theoretical models of the isospin-symmetry-breaking corrections in this mass region.

Background: Parity-violating electron scattering provides a model-independent determination of the nuclear weak-charge form factor that has widespread implications across such diverse areas as fundamental symmetries, nuclear structure, heavy-ion collisions, and neutron-star structure.

Purpose: We assess the impact of precise measurements of the weak-charge form factor of ${}^{48}$Ca and ${}^{208}$Pb on a variety of nuclear observables, such as the neutron skin and the electric-dipole polarizability.

Methods: We use the nuclear density functional theory with several accurately calibrated nonrelativistic and relativistic energy density functionals. To assess the degree of correlation between nuclear observables and to explore systematic and statistical uncertainties on theoretical predictions, we employ the chi-square statistical covariance technique.

Results: We find a strong correlation between the weak-charge form factor and the neutron radius, that allows for an accurate determination of the neutron skin of neutron-rich nuclei. We determine the optimal range of the momentum transfer $q$ that maximizes the information content of the measured weak-charge form factor and quantify the uncertainties associated with the strange quark contribution. Moreover, we confirm the role of the electric-dipole polarizability as a strong isovector indicator.

Conclusions: Accurate measurements of the weak-charge form factor of ${}^{48}$Ca and ${}^{208}$Pb will have a profound impact on many aspects of nuclear theory and hadronic measurements of neutron skins of exotic nuclei at radioactive-beam facilities.

By using mirror symmetry and information from ${}^{11}$Li, we have used a simple potential model to estimate the energies of the $s^2$ and $p$-shell components of ${}^{11}$O(g.s.). We present the predicted ${}^{11}$O mass in terms of the mixing of these two components.

We study the development of collectivity in neutron rich nuclei in the close vicinity of ${}^{78}$Ni. We report on the large scale shell model calculations in the $N=52–54$ even-even nuclei with $Z=30–36$. We predict maximum of triaxiality in ${}^{86}$Ge and explain this phenomenon on the basis of a pseudo-SU(3) symmetry interpretation. For the cases where signs for nonaxial shapes appear, we perform the triaxial Gogny calculations with particle number and angular momentum projections. The comparison of results obtained in the laboratory and intrinsic frames provides a comprehensive and complete picture of nuclear deformation in this region.

I review the situation regarding the ground and low-lying states of ${}^{10}$He, with special emphasis on the reaction ${}^8$He(t,p). I present calculations of relative cross sections for $0^{+}$ and $1^{-}$ states. I conclude that the strong state reported near 5.5 MeV is probably not $1^{-}$.