We formulate a model for ${}^{212}\mathrm{Po}$, based on the coupled-channels of $\alpha +{}^{208}\mathrm{Pb}$($0^{+}$) and $\alpha +{}^{208}\mathrm{Pb}$($3^{-}$) in which the $\alpha$-Pb interaction contains scalar, quadrupole, and octupole terms. The model reproduces the recently observed enhanced $E1$ transitions from the several new negative-parity levels to the yrast states. Because these data are hard to understand in the shell model, this success gives a strong support for a unique role of $\alpha +{}^{208}\mathrm{Pb}$($3^{-}$) clustering in ${}^{212}\mathrm{Po}$.

We report on the first determination of the magnetic moment of the 981.1 keV, $J^{\pi }=8^{+}$ level in ${}^{72}\mathrm{As}$, a nucleus that belongs to the $A\approx 70$ mass region dominated by rapidly changing deformations and shapes. The $8^{+}$ level is the bandhead of a collective sequence of positive parity levels coexisting with low-spin and medium-spin spherical shell-model states. The magnetic moment was measured by the time-integral perturbed angular distributions method to be $\mu =-(4.272\pm 0.280){\mu }_N$. This value is in disagreement with the presumed $[\pi (1g_{9/2}),\nu (1g_{9/2})]$ configuration and points to a more complex configuration involving two neutrons in the $1g_{9/2}\hspace{0.5em}$orbital.

The measurement of the excitation function for fusion evaporation reactions in the system ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$ ($Q=$ 4.56 MeV) has been extended downward by two orders of magnitude with respect to previous cross section data. A first indication of an $S$-factor maximum in a system with a positive $Q$ value has been observed. In addition a correlation between fusion hindrance and neutron excess $N-Z$ has been found for the Ca $+$ Ca, Ni $+$ Ni, and Ca $+$ Zr systems.

The excitation function for the complete fusion of ${}^9\mathrm{Be}$$+$${}^{89}\mathrm{Y}$ has been measured at near-barrier energies, and the barrier distribution has been extracted from the fusion data. Coupled-channels calculations have been carried out to understand the effect of coupling of both the projectile and target excitations on the above quantities. The complete fusion cross sections, especially at above-barrier energies, have been found to be suppressed by ($20\pm 5$)% compared to the ones predicted by the coupled-channels calculations that do not include the couplings to the projectile continuum, indicating the loss of flux from the entrance channel before fusion. This conclusion is also supported by a considerable incomplete fusion cross section observed for this system. Fusion measurements for two more systems have been carried out, namely, for ${}^4\mathrm{He}$$+$${}^{93}\mathrm{Nb}$ and ${}^{12}\mathrm{C}$$+$${}^{89}\mathrm{Y}$, which involve tightly bound projectiles and form compound nuclei nearby to that formed in ${}^9\mathrm{Be}$$+$${}^{89}\mathrm{Y}$ fusion. Comparison of the fusion data obtained for all three systems further confirms the suppression of complete fusion in the ${}^9\mathrm{Be}$$+$${}^{89}\mathrm{Y}$ system. Systematics of the suppression factor observed for ${}^9\mathrm{Be}$ induced fusion in different mass targets is discussed.

We study the $Q^2$ evolution of the form factors (FFs) for the nucleon-to-$N^{*}(1680)$ transition in the framework of effective field theory. To this end, the intrinsic symmetries of the spin-$\frac{5}{2}$ Rarita-Schwinger (RS) fields are analyzed, and a Lagrangian of the electromagnetic ${\mathit{NN}}^{*}(1680)$ interactions is constructed. The Lagrangian preserves all the intrinsic symmetries of the spin-$\frac{5}{2}$ field—point and gauge invariance—and does not involve lower-spin components of the reducible RS field. In addition, the symmetries postulate the definitions of the Lagrangian FFs. These FFs are modeled as dispersionlike expansions in a vector-meson-dominance model. A good agreement with the experimental data is achieved.

We investigate the $\Lambda (1520)$ photoproduction in the $\mathrm{\gamma ⃗}p\to K^{+}\Lambda (1520)$ reaction within the effective Lagrangian method near threshold. In addition to the “background” contributions from the contact, $t$-channel $K$-exchange, and $s$-channel nucleon pole terms, which were already considered in previous studies, the contribution from the nucleon resonance $N^{*}(2080)$ (spin-parity $J^P=3/2^{-}$) is also considered. We show that the inclusion of the nucleon resonance $N^{*}(2080)$ leads to a fairly good description of the new LEPS differential cross-section data, and that these measurements can be used to determine some of the properties of this latter resonance. However, serious discrepancies appear when the predictions of the model are compared to the photon-beam asymmetry,which was also measured by the LEPS Collaboration.

The level structure of ${}^{22}\mathrm{Na}$ has been studied at the Holifield Radioactive Ion Beam Facility in Oak Ridge National Laboratory using the ${}^{24}\mathrm{Mg}$($p$,${}^3\mathrm{He}$)${}^{22}\mathrm{Na}$ reaction. Proton beams of 41 and 41.5 MeV were generated by the 25-MV tandem accelerator and bombarded isotopically enriched ${}^{24}\mathrm{Mg}$ targets. Angular distributions of recoiling ${}^3\mathrm{He}$ particles were extracted by using a segmented annular silicon strip detector array. Spins and parities for 10 levels were constrained through a distorted-wave Born approximation analysis of angular distributions, including three levels above the proton threshold at 6.739 MeV.

Particle correlation measurements associated with a hard or semihard trigger in heavy-ion collisions may reflect Mach cone shock waves excited in the bulk medium by partonic energy loss. This is of great interest because, when compared with theory, such measurements can provide information on the transport properties of the medium. Specifically, the formation of Mach cone shock waves is sensitive to the viscosity and speed of sound, as well as the detailed nature of the jet-medium interaction. However, modeling the physics of shock-wave excitation to obtain a meaningful comparison with measured correlations is very challenging, as the correlations arise from an interplay of perturbative as well as nonperturbative phenomena at different momentum scales. In this work we take a step in that direction by presenting a systematic study of the dependence of azimuthal particle correlations on the spatiotemporal structure of energy deposition into the medium. Our results indicate that detailed modeling of the evolution of an initially produced hard parton and the interaction of this evolving state with the medium is crucial, as both the magnitude and the shape of the shock-wave signal show a strong dependence on the assumptions being made.

In the present article, we investigate stellar matter obtained within the quark-meson-coupling (QMC) model for fixed temperature and with the entropy of the order of $1$ or $2$ Boltzmann units per baryon for neutrino-free matter and matter with trapped neutrinos. A new prescription for the calculation of the baryon effective masses in terms of the free energy is used. Comparing the results of the present work with those obtained from the nonlinear Walecka model, smaller strangeness and neutrino fractions are predicted within QMC. As a consequence, QMC has a smaller window of metastability for conversion into a low-mass blackhole during cooling.

Isomeric states in ${}^{112}\mathrm{Tc}$ and ${}^{113}\mathrm{Tc}$, with half-lives of 150(17) ns and 500(100) ns, respectively, have been observed following the relativistic fission of ${}^{238}\mathrm{U}$. The fission fragments have been separated in a fragment separator and identified by means of energy-loss and time-of-flight techniques. In both nuclei, the ground-state configuration is calculated to have an oblate shape and the isomerism is proposed to arise due to transitions from a triaxial excited state to a low-lying oblate state.

Taking into account entropy generation during evolution of a viscous fluid, we have estimated the inverse Knudsen number, the ideal hydrodynamic limit for elliptic flow, and the quark-gluon plasma viscosity to entropy ratio in $\sqrt{s_{\mathit{NN}}}=62$ and 200 GeV Cu+Cu/Au+Au collisions. The viscosity to entropy ratio is estimated as $\eta /s=0.17\pm 0.10\pm 0.20$, where the first error is statistical, the second one is systematic. In a central Au+Au collision, the inverse Knudsen number is $\approx$$2.80\pm 1.63$, which is presumably too small for complete equilibration. In peripheral collisions it is even less. The ideal hydrodynamic limit for elliptic flow is $~40\%$ more than the experimental flow in a central collision.

This article reports on the ground-state spin and moments measured in ${}^{72,74}\mathrm{Cu}$ using collinear laser spectroscopy at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. From the measured hyperfine coefficients, the nuclear observables $\mu$(${}^{72}\mathrm{Cu})=-1.3472(10){\mu }_N$, $\mu ({}^{74}\mathrm{Cu})=-1.068(3){\mu }_N$, $Q({}^{72}\mathrm{Cu})=+8(2)\hspace{0.5em}{\mathrm{efm}}^2$, $Q({}^{74}\mathrm{Cu})=+26(3)\hspace{0.5em}{\mathrm{efm}}^2$, $I({}^{72}\mathrm{Cu})=2$, and $I({}^{74}\mathrm{Cu})=2$ have been determined. Through a comparison of the measured magnetic moments with different models, the negative moment reveals a strong $\pi f_{5/2}\otimes \nu g_{9/2}$ component in the ground-state wave function. Consequently, a negative parity has been assigned to the ground states of ${}^{72,74}\mathrm{Cu}$. Large-scale shell-model calculations illustrate the strong sensitivity of the nuclear moments to configuration mixing and to the effective interaction employed.

The transverse densities in a fast-moving nucleon offer a model-independent framework for analyzing the spatial structure of the pion cloud and its role in current matrix elements. We calculate the chiral large-distance component of the charge density in a dispersion representation of the form factor and discuss its partonic interpretation. It dominates over the nonchiral density only at surprisingly large distances above $~2$ fm. The chiral component can be probed in precision low-$Q^2$ elastic $\mathit{eN}$ scattering or in peripheral deep-inelastic processes that resolve its quark/gluon content.

Reaction cross sections (${\sigma }_R$) for the proton drip-line nucleus ${}^{17}\mathrm{Ne}$ have been measured on ${}^9\mathrm{Be}$, ${}^{12}\mathrm{C}$, and ${}^{27}\mathrm{Al}$ targets at 64 and 42 MeV/nucleon by the transmission method. From the energy dependence of the ${\sigma }_R$ including the high energy data, the density distribution of ${}^{17}\mathrm{Ne}$ was deduced through a modified Glauber-type calculation. It is indicated that ${}^{17}\mathrm{Ne}$ has a long tail in the density, consistent with a $(2s_{1/2}){}^2$-dominant configuration of two valence protons.

Lifetimes of excited states in ${}^{98}\mathrm{Zr}$ have been investigated with a $\beta \gamma \gamma$ fast-timing experiment performed at the Lohengrin mass separator at the Institut Laue-Langevin. Five lifetimes of both yrast and off-yrast states have been measured, including the lowest upper limit for $\tau (2_1^{+})$. The results are compared with recent shell-model and interacting-boson-model calculations.

By assuming that the isospin- and momentum-dependent MDI interaction has a form similar to the Gogny-like effective two-body interaction with a Yukawa finite-range term and the momentum dependence originates only from the finite-range exchange interaction, we determine its parameters by comparing the predicted potential energy density functional in uniform nuclear matter with what has been usually given and used extensively in transport models for studying isospin effects in intermediate-energy heavy-ion collisions as well as in investigating the properties of hot asymmetric nuclear matter and neutron star matter. We then use the density matrix expansion to derive from the resulting finite-range exchange interaction an effective Skyrme-like zero-range interaction with density-dependent parameters. As an application, we study the transition density and pressure at the inner edge of neutron star crusts using the stability conditions derived from the linearized Vlasov equation for the neutron star matter.

We compiled the experimentally measured $\mathrm{p̄}/p$ ratio at midrapidity in $p+p$ collisions from $\sqrt{s}=23$ to $7000$ GeV and compared it to various mechanisms of baryon production as implemented in the pythia, phojet, and Heavy Ion Jet Interaction Generator (HIJING)/B-$\overline{\mathrm{B}}$ models. For the models studied with default settings, phojet has the best agreement with the measurements, pythia gives a higher value for $\sqrt{s}<200$ GeV, and the ratios from HIJING/B-$\overline{\mathrm{B}}$ are consistently lower for all the $\sqrt{s}$ studied. A comparison of the data to different mechanisms of baryon production as implemented in pythia shows that through a suitable tuning of the suppression of diquark-antidiquark pair production in the color field relative to quark-antiquark production and allowing the diquarks to split according to the popcorn scheme, a fairly reasonable description of the measured $\mathrm{p̄}/p$ ratio for $\sqrt{s}<200$ GeV is given. A comparison of the beam energy dependence of the $\mathrm{p̄}/p$ ratio in $p+p$ and nucleus-nucleus (A $+$ A) collisions at midrapidity shows that the baryon production is significantly more for A $+$ A collisions relative to $p+p$ collisions for $\sqrt{s}<200$ GeV. We also carry out a phenomenological fit to the $y_{\mathrm{beam}}$ dependence of the $\mathrm{p̄}/p$ ratio.

The photon spectrum accompanying the orbital $K$-electron capture in the first-forbidden unique decay of ${}^{81}\mathrm{Kr}$ was measured. The total radiation intensity for photon energies larger than 50 keV was found to be $1.42(22)\times {10}^{-4}$ per $K$ capture. Both the shape of the spectrum and its intensity relative to the ordinary, nonradiative capture rate are compared to theoretical predictions. The best agreement is found for the recently developed model that employs the length gauge for the electromagnetic field.

Models of relativistic heavy-ion collisions typically involve both a hydrodynamic module to describe the high-density liquidlike phase and a Boltzmann module to simulate the low-density breakup phase, which is gaslike. Coupling the prescriptions is more complicated for viscous prescriptions if one wants to maintain continuity of the entire stress-energy tensor and currents. Derivations for the viscosity for a gas are reviewed, which then lead to expressions for changes in the phase-space occupation based on simple relaxation-time pictures of viscosity. These expressions are shown to consistently reproduce the nonequilibrium components of the stress-energy tensor. An algorithm for generating a Monte Carlo sampling of particles with which to initiate the Boltzmann calculations is also presented.