Triggering of long-lived nuclear isomeric states via coupling to the atomic shells in the process of nuclear excitation by electron capture (NEEC) is studied. NEEC occurring in highly charged ions can excite the isomeric state to a triggering level that subsequently decays to the ground state. We present total cross sections for NEEC isomer triggering considering experimentally confirmed low-lying triggering levels and reaction rates based on realistic experimental parameters in ion storage rings. A comparison with other isomer triggering mechanisms shows that, among these, NEEC is the most efficient.

Relativistic viscous hydrodynamic fits to Brookhaven Relativistic Heavy Ion Collider data on the centrality dependence of multiplicity, transverse, and elliptic flow for $\sqrt{s}=200\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions are presented. For standard (Glauber-type) initial conditions, while data on the integrated elliptic flow coefficient $v_2$ are consistent with a ratio of viscosity over entropy density up to $\eta /s\simeq 0.16$, data on minimum bias $v_2$ seem to favor a much smaller viscosity over entropy ratio, below the bound from the anti–de Sitter conformal field theory conjecture. Some caveats on this result are discussed.

Electromagnetic transition probabilities have been measured for the intraband and interband transitions in the two sequences in the nucleus ${}^{135}\mathrm{Nd}$ that were previously identified as a composite chiral pair of rotational bands. The chiral character of the bands is affirmed and it is shown that their behavior is associated with a transition from a vibrational into a static chiral regime.

We introduce spin projection methods in the shell model Monte Carlo approach and apply them to calculate the spin distribution of level densities for iron-region nuclei using the complete ($pf+g_{9/2}$) shell. We compare the calculated distributions with the spin-cutoff model and extract an energy-dependent moment of inertia. For even-even nuclei and at low excitation energies, we observe a significant suppression of the moment of inertia and odd-even staggering in the spin dependence of level densities.

Rare isotope beams of neutron-deficient ${}^{106,108,110}\mathrm{Sn}$ from the fragmentation of ${}^{124}\mathrm{Xe}$ were employed in an intermediate-energy Coulomb excitation experiment. The measured $B(E2,0_1^{+}\to 2_1^{+})$ values for ${}^{108}\mathrm{Sn}$ and ${}^{110}\mathrm{Sn}$ and the results obtained for the ${}^{106}\mathrm{Sn}$ show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the $Z=50$ shell to the structure of low-energy excited states in this region.

The time delay in fission induced by bombardment of W with 180 MeV ${}^{32}\mathrm{S}$, 240–255 MeV ${}^{48}\mathrm{Ti}$, and 315–375 MeV ${}^{58}\mathrm{Ni}$ has been measured by observation of crystal blocking. There is a clear narrowing and a small increase in the minimum yield of the angular dips for fission compared with scaled dips for elastically scattered ions. This is interpreted as a fission delay of about 2 as, only weakly dependent on energy and atomic number. The delay is longer by 1 to 2 orders of magnitude than obtained from standard interpretations of measurements of prescission neutrons and giant-dipole-resonance gamma rays and from calculations of the nuclear dynamics in heavy-ion reactions.

The strength distributions of the giant monopole resonance (GMR) have been measured in the even-$A$ Sn isotopes ($A=112–124$) with inelastic scattering of 400-MeV $\alpha$ particles in the angular range 0°–8.5°. We find that the experimentally observed GMR energies of the Sn isotopes are lower than the values predicted by theoretical calculations that reproduce the GMR energies in ${}^{208}\mathrm{Pb}$ and ${}^{90}\mathrm{Zr}$ very well. From the GMR data, a value of $K_{\tau }=-550\pm 100\mathrm{MeV}$ is obtained for the asymmetry term in the nuclear incompressibility.

Medium modification of dihadron fragmentation functions due to gluon bremsstrahlung induced by multiple partonic scattering is studied in both deep-inelastic scattering (DIS) off large nuclei and high-energy heavy-ion collisions within the same framework of twist expansion. The modification for dihadrons is found to closely follow that for single hadrons, leading to a weak nuclear suppression of their ratios in DIS experiments. A mild enhancement of the near-side correlation of two high transverse momentum hadrons with increasing centrality is found in heavy-ion collisions due to trigger bias and the rise in parton energy loss with centrality. Successful comparisons between theory and experiment for multihadron observables in both confining and deconfined media offer comprehensive evidence for partonic energy loss as the mechanism of jet modification in dense matter.

Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the $2_1^{+}$ state in ${}^{78}\mathrm{Zn}$ could be firmly established and for the first time the $2^{+}\to 0_1^{+}$ transition in ${}^{80}\mathrm{Zn}$ was observed at 1492(1) keV. $B(E2,2_1^{+}\to 0_1^{+})$ values were extracted for ${}^{74,76,78,80}\mathrm{Zn}$ and compared to large scale shell model calculations. With only two protons outside the $Z=28$ proton core, ${}^{80}\mathrm{Zn}$ is the lightest $N=50$ isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed $B(E2)$ systematics. The results for $N=50$ isotones indicate a good $N=50$ shell closure and a strong $Z=28$ proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus ${}^{78}\mathrm{Ni}$.

We examine the decay of the 3.03 MeV state of ${}^8\mathrm{Be}$ evaporated from an excited projectilelike fragment following a peripheral heavy-ion collision. The relative energy of the daughter $\alpha$ particles exhibits a dependence on the decay angle of the ${}^8\mathrm{Be}^{*}$, indicative of a tidal effect. A comparison of the measured tidal effect with a model suggests a measurable nuclear proximity interaction.

The beam-recoil double polarization $P_{x^{\prime }}^h$ and $P_{z^{\prime }}^h$ and the recoil polarization $P_{y^{\prime }}$ were measured for the first time for the $p(\overrightarrow{e},e^{\prime }\overrightarrow{p})\eta$ reaction at a four-momentum transfer of $Q^2=0.1{\mathrm{GeV}}^2/c^2$ and a center of mass production angle of $\theta =120°$ at the Mainz Microtron MAMI-C. With a center of mass energy range of $1500\mathrm{MeV}<W<1550\mathrm{MeV}$ the region of the $S_{11}(1535)$ and $D_{13}(1520)$ resonance was covered. The results are discussed in the framework of a phenomenological isobar model (Eta-MAID). While $P_{x^{\prime }}^h$ and $P_{z^{\prime }}^h$ are in good agreement with the model, $P_{y^{\prime }}$ shows a significant deviation, consistent with existing photoproduction data on the polarized-target asymmetry.

The NA60 experiment studies muon pair production at the CERN Super Proton Synchrotron. In this Letter we report on a precision measurement of $J/\psi$ in In-In collisions. We have studied the $J/\psi$ centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism. For collisions involving more than $\sim 80$ participant nucleons, we find that an extra suppression is present. This result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment, but no theoretical explanation is presently able to coherently describe both results.

The $\gamma$ decay of excited states in the waiting-point nucleus ${}^{130}\mathrm{Cd}_{82}$ has been observed for the first time. An $8^{+}$ two-quasiparticle isomer has been populated both in the fragmentation of a ${}^{136}\mathrm{Xe}$ beam as well as in projectile fission of ${}^{238}\mathrm{U}$, making ${}^{130}\mathrm{Cd}$ the most neutron-rich $N=82$ isotone for which information about excited states is available. The results, interpreted using state-of-the-art nuclear shell-model calculations, show no evidence of an $N=82$ shell quenching at $Z=48$. They allow us to follow nuclear isomerism throughout a full major neutron shell from ${}^{98}\mathrm{Cd}_{50}$ to ${}^{130}\mathrm{Cd}_{82}$ and reveal, in comparison with ${}^{76}\mathrm{Ni}_{48}$ one major proton shell below, an apparently abnormal scaling of nuclear two-body interactions.

We have observed a resonance in neutron-fragment coincidence measurements that is presumably the first excited state of ${}^{23}\mathrm{O}$ at 2.8(1) MeV excitation energy which decays into the ground state of ${}^{22}\mathrm{O}$. This interpretation is consistent with theory. The reaction mechanism supports the assignment of the observed state as the $5/2^{+}$ hole state. This assignment and the recently observed $3/2^{+}$ particle state advance the understanding of ${}^{23}\mathrm{O}$.

We present first measurements of the $\varphi$-meson elliptic flow ($v_2(p_T)$) and high-statistics $p_T$ distributions for different centralities from $\sqrt{s_{NN}}=200\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC. In minimum bias collisions the $v_2$ of the $\varphi$ meson is consistent with the trend observed for mesons. The ratio of the yields of the $\Omega$ to those of the $\varphi$ as a function of transverse momentum is consistent with a model based on the recombination of thermal $s$ quarks up to $p_T\sim 4\mathrm{GeV}/c$, but disagrees at higher momenta. The nuclear modification factor ($R_{\mathrm{CP}}$) of $\varphi$ follows the trend observed in the $K_S^0$ mesons rather than in $\Lambda$ baryons, supporting baryon-meson scaling. These data are consistent with $\varphi$ mesons in central $\mathrm{Au}+\mathrm{Au}$ collisions being created via coalescence of thermalized $s$ quarks and the formation of a hot and dense matter with partonic collectivity at RHIC.

The decay of the ground-state two-proton emitter ${}^{45}\mathrm{Fe}$ was studied with a time-projection chamber and the emission of two protons was unambiguously identified. The total decay energy and the half-life measured in this work agree with the results from previous experiments. The present result constitutes the first direct observation of the individual protons in the two-proton decay of a long-lived ground-state emitter. In parallel, we identified for the first time directly two-proton emission from ${}^{43}\mathrm{Cr}$, a known $\beta$-delayed two-proton emitter. The technique developed in the present work opens the way to a detailed study of the mechanism of ground state as well as $\beta$-delayed two-proton radioactivity.

High-energy-resolution inelastic electron scattering (at the S-DALINAC) and proton scattering (at iThemba LABS) experiments permit a thorough test of the nature of proposed one- and two-phonon symmetric and mixed-symmetric $2^{+}$ states of the nucleus ${}^{94}\mathrm{Mo}$. The combined analysis reveals the one-phonon content of the mixed-symmetry state and its isovector character suggested by microscopic nuclear model calculations. The purity of two-phonon $2^{+}$ states is extracted.

The relativistic mean-field framework, extended to include correlations related to restoration of broken symmetries and to fluctuations of the quadrupole deformation, is applied to a study of shape transitions in Nd isotopes. It is demonstrated that the microscopic self-consistent approach, based on global effective interactions, can describe not only general features of transitions between spherical and deformed nuclei, but also the singular properties of excitation spectra and transition rates at the critical point of quantum shape phase transition.

We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely polarized 3 GeV electrons from unpolarized protons at $Q^2=0.15$, $0.25(\mathrm{GeV}/c{)}^2$. The results are inconsistent with calculations solely using the elastic nucleon intermediate state and generally agree with calculations with significant inelastic hadronic intermediate state contributions. $A_n$ provides a direct probe of the imaginary component of the $2\gamma$ exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.

We propose an importance truncation scheme for no-core shell model or configuration interaction approaches, which enables converged calculations for nuclei well beyond the $p$ shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for ${}^4\mathrm{He}$ and ${}^{16}\mathrm{O}$. Then, we present first converged calculations for the ground state of ${}^{40}\mathrm{Ca}$ within no-core model spaces including up to $16\hslash \Omega$ excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.