It is shown that the multinucleon transfer reactions in low-energy collisions of heavy ions may be used for production of new neutron-rich nuclei at the “northeast” part of the nuclear map along the neutron closed shell $N=126$ which plays an important role in the $r$ process of nucleosynthesis. More than 50 unknown nuclei might be produced in such reactions (in particular, in collision of ${}^{136}\mathrm{Xe}$ with ${}^{208}\mathrm{Pb}$) with cross sections of not less than $1\mu \mathrm{b}$.

We show the effects of the granular structure of the initial conditions of a hydrodynamic description of high-energy nucleus-nucleus collisions on some observables, especially on the elliptic-flow parameter $v_2$. Such a structure enhances production of isotropically distributed high-$p_T$ particles, making $v_2$ smaller there. Also, it reduces $v_2$ in the forward and backward regions where the global matter density is smaller and, therefore, where such effects become more efficacious.

We report measurements of the ${\pi }^{-}p\to {\pi }^{0}n$ differential cross sections at six momenta ($104–143\mathrm{MeV}/c$) and four angles (0°–40°) by detection of $\gamma$-ray pairs from ${\pi }^0\to \gamma \gamma$ decays using a photon-pair spectrometer at TRIUMF. This kinematic region exhibits a vanishing zero-degree cross section from destructive interference between $s$ and $p$ waves, thus yielding special sensitivity to pion-nucleon dynamics. Our data and previous data do not agree, with important implications for earlier claims of large isospin-violating effects.

The fundamental reaction $pp\to \{pp{\}}_s\gamma$, where $\{pp{\}}_s$ is a proton pair with low excitation energy, has been observed with the ANKE spectrometer at COSY-Jülich for proton beam energies of $T_p=0.353$, 0.500, and 0.550 GeV. This is equivalent to photodisintegration of a free ${}^{1}S_0$ diproton for photon energies $E_{\gamma }\approx T_p/2$. The differential cross sections measured for c.m. angles $0°<{\theta }_{pp}<20°$ exhibit a steep increase with angle that is compatible with $E1$ and $E2$ multipole contributions. The ratio of the measured cross sections to those of $np\to \gamma d$ is on the ${10}^{-3}–{10}^{-2}$ level. The increase of the $pp\to \{pp{\}}_s\gamma$ cross section with $T_p$ might reflect the influence of the $\Delta (1232)$ excitation.

We develop a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei, by combining the resonating-group method with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. This approach preserves translational symmetry and Pauli principle. We present phase shifts for neutron scattering on ${}^3\mathrm{H}$, ${}^4\mathrm{He}$, and ${}^{10}\mathrm{Be}$ and proton scattering on ${}^{3,4}\mathrm{He}$, using realistic nucleon-nucleon potentials. Our $A=4$ scattering results are compared to earlier ab initio calculations. We demonstrate that a proper treatment of the coupling to the $n\mathrm{\text{−}}{}^{10}\mathrm{Be}$ continuum is successful in explaining the parity-inverted ground state in ${}^{11}\mathrm{Be}$.

We compute the binding energies, radii, and densities for selected medium-mass nuclei within coupled-cluster theory and employ a bare chiral nucleon-nucleon interaction at next-to-next-to-next-to-leading order. We find rather well-converged results in model spaces consisting of 15 oscillator shells, and the doubly magic nuclei ${}^{40}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}$, and the exotic ${}^{48}\mathrm{Ni}$ are underbound by about 1 MeV per nucleon within the coupled-cluster singles-doubles approximation. The binding-energy difference between the mirror nuclei ${}^{48}\mathrm{Ca}$ and ${}^{48}\mathrm{Ni}$ is close to theoretical mass table evaluations. Our computation of the one-body density matrices and the corresponding natural orbitals and occupation numbers provides a first step to a microscopic foundation of the nuclear shell model.

Comprehensive fission measurements, including mass-angle distributions, for the reaction of ${}^{32}\mathrm{S}$ with the prolate deformed nucleus ${}^{232}\mathrm{Th}$ at near-barrier energies show two distinct components in both mass and angle; surprisingly, both have characteristics of quasifission. Their relative probabilities vary rapidly with the ratio of the beam energy to the capture barrier, suggesting a relationship with deformation aligned (sub-barrier), or antialigned (above-barrier), configurations at contact.

The elliptic flow $v_2$ and the ratio of the shear viscosity over the entropy density, $\eta /s$, of gluon matter are calculated from the perturbative QCD (pQCD) based parton cascade Boltzmann approach of multiparton scatterings. For $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s}=200A\mathrm{GeV}$ the gluon plasma generates large $v_2$ values measured at the BNL Relativistic Heavy Ion Collider. Standard pQCD yields $\eta /s\approx 0.08–0.15$ as small as the lower bound found from the anti–de Sitter/conformal field theory conjecture.

To explore the four-$\alpha$-particle condensate state in ${}^{16}\mathrm{O}$, we solve a full four-body equation of motion based on the four-$\alpha$-particle orthogonality condition model in a large four-$\alpha$-particle model space spanned by Gaussian basis functions. A full spectrum up to the $0_6^{+}$ state is reproduced consistently with the lowest six $0^{+}$ states of the experimental spectrum. The $0_6^{+}$ state is obtained at about 2 MeV above the four-$\alpha$-particle breakup threshold and has a dilute density structure, with a radius of about 5 fm. The state has an appreciably large $\alpha$ condensate fraction of 61%, and a large component of $\alpha +{}^{12}\mathrm{C}(0_2^{+})$ configuration, both features being reliable evidence for this state to be of four-$\alpha$-particle condensate nature.

Measurements in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ of jet correlations for a trigger hadron at intermediate transverse momentum ($p_{T,\mathrm{trig}}$) with associated mesons or baryons at lower $p_{T,\mathrm{assoc}}$ indicate strong modification of the away-side jet. The ratio of jet-associated baryons to mesons increases with centrality and $p_{T,\mathrm{assoc}}$. For the most central collisions, the ratio is similar to that for inclusive measurements. This trend is incompatible with in-vacuum fragmentation but could be due to jetlike contributions from correlated soft partons, which recombine upon hadronization.

We extend the shell model Monte Carlo approach to heavy deformed nuclei using a new proton-neutron formalism. The low excitation energies of such nuclei necessitate low-temperature calculations, for which a stabilization method is implemented in the canonical ensemble. We apply the method to study a well-deformed rare-earth nucleus, ${}^{162}\mathrm{Dy}$. The single-particle model space includes the 50–82 shell plus $1f_{7/2}$ orbital for protons and the 82–126 shell plus $0h_{11/2}$, $1g_{9/2}$ orbitals for neutrons. We show that the spherical shell model reproduces well the rotational character of ${}^{162}\mathrm{Dy}$ within this model space. We also calculate the level density of ${}^{162}\mathrm{Dy}$ and find it to be in excellent agreement with the experimental level density, which we extract from several experiments.

Reaction mechanism analyses performed with a $4\pi$ detector for the systems ${}^{208}\mathrm{Pb}+\mathrm{Ge}$, ${}^{238}\mathrm{U}+\mathrm{Ni}$ and ${}^{238}\mathrm{U}+\mathrm{Ge}$, combined with analyses of the associated reaction time distributions, provide us with evidence for nuclei with $Z=120$ and 124 living longer than ${10}^{-18}\mathrm{s}$ and arising from highly excited compound nuclei. By contrast, the neutron deficient nuclei with $Z=114$ possibly formed in ${}^{208}\mathrm{Pb}+\mathrm{Ge}$ reactions have shorter lifetimes, close to or below the sensitivity limit of the experiment.

Atomic masses of the neutron-rich isotopes ${}^{76–80}\mathrm{Zn}$, ${}^{78–83}\mathrm{Ga}$, ${}^{80–85}\mathrm{Ge}$, ${}^{81–87}\mathrm{As}$, and ${}^{84–89}\mathrm{Se}$ have been measured with high precision using the Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The masses of ${}^{82,83}\mathrm{Ga}$, ${}^{83–85}\mathrm{Ge}$, ${}^{84–87}\mathrm{As}$, and ${}^{89}\mathrm{Se}$ were measured for the first time. These new data represent a major improvement in the knowledge of the masses in this neutron-rich region. Two-neutron separation energies provide evidence for the reduction of the $N=50$ shell gap energy towards germanium ($Z=32$) and a subsequent increase at gallium ($Z=31$). The data are compared with a number of theoretical models. An indication of the persistent rigidity of the shell gap towards nickel ($Z=28$) is obtained.

We compare coupled-cluster (CC) and configuration-interaction (CI) results for ${}^{55}\mathrm{Ni}$ and ${}^{57}\mathrm{Ni}$ obtained in the $pf$-shell basis, focusing on the practical equation-of-motion (EOM) CC approximations that can be applied to systems with dozens of correlated fermions. The weight of the reference state and the strength of correlation effects are controlled by the gap between the $f_{7/2}$ orbit and the $f_{5/2}$, $p_{3/2}$, $p_{1/2}$ orbits. Independent of the gap, the CC methods with up to $2p\mathrm{\text{−}}2h$ components in the cluster operator and $3p\mathrm{\text{−}}2h/3h\mathrm{\text{−}}2p$ components in the EOMCC excitation operator are more accurate than the computationally more demanding CI approach with up to $3p\mathrm{\text{−}}3h$ excitations and almost as accurate as the even more demanding CI approach truncated at $4p\mathrm{\text{−}}4h$ excitations.

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio $G_E^n/G_M^n$ was extracted from the beam-target vector asymmetry $A_{\mathrm{ed}}^V$ at four-momentum transfers $Q^2=0.14$, 0.20, 0.29, and $0.42(\mathrm{GeV}/c{)}^2$.

Results from the $\gamma$-ray spectroscopy of ${}^{47,48}\mathrm{Ar}$ exemplifying new limits of sensitivity for characterizing neutron-rich nuclei at energies around the Coulomb barrier are presented. The present results, along with interacting shell model calculations, highlight the role of cross-shell excitations and indicate the presence of a nonaxial deformation in ${}^{48}\mathrm{Ar}$.

Cross-section and neutron-emission data from heavy-ion fusion-fission reactions are consistent with a Kramers-modified statistical model which takes into account the collective motion of the system about the ground state, the temperature dependence of the location of fission transition points, and the orientation degree of freedom. The strong increase in the nuclear viscosity above a temperature of $\sim 1\mathrm{MeV}$ deduced by others is an artifact generated by an inadequate fission model.

Angular distributions for $1n$ and $2n$ transfer are reported for the ${}^6\mathrm{He}+{}^{65}\mathrm{Cu}$ system at $E_{\mathrm{lab}}=22.6\mathrm{MeV}$. For the first time, triple coincidences between $\alpha$ particles, neutrons, and characteristic $\gamma$ rays from the targetlike residues were used to separate the contributions arising from $1n$ and $2n$ transfer. The differential cross sections for these channels, elastic scattering, and fusion were analyzed using a coupled reaction channels approach. The large measured ratio of the $2n$-to-$1n$ cross section and the strong influence of $2n$ transfer on other channels indicate that the dineutron configuration of ${}^6\mathrm{He}$ plays a dominant role in the reaction mechanism.

We present a measurement of the spin-dependent cross sections for the ${}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\prime })X$ reaction in the quasielastic and resonance regions at a four-momentum transfer $0.1\le Q^2\le 0.9{\mathrm{GeV}}^2$. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt-Cottingham and extended Gerasimov-Drell-Hearn sum rules for the first time. The data are also compared to an impulse approximation calculation and an exact three-body Faddeev calculation in the quasielastic region.

The radiative energy loss of a quark jet traversing a finite size QCD medium with dynamical constituents is calculated to first order in opacity. Although finite size corrections reduce the energy loss relative to an infinite dynamical QCD medium, under realistic conditions it remains significantly larger than in a static medium. Quantitative predictions of jet suppression in relativistic heavy ion collisions must therefore account for the dynamics of the medium’s constituents. Finite size effects are shown to induce a nonlinear path length dependence of the energy loss. Our results suggest a simple general mapping between energy loss expressions for static and dynamical QCD media.