Isobaric analog states of ${}^7\mathrm{He}$ have been investigated by a novel technique involving the observation of the resonant yield of neutrons from the ${}^6\mathrm{He}(p,n)$ reaction in coincidence with $\gamma$ rays from the decay of the $(0^{+},T=1)$ state in ${}^6\mathrm{Li}$. The $\gamma$ rays provide a clean signature for the isospin-conserving neutron decay of the low-lying isobaric analog resonances. It is conclusively shown that the analog of the recently observed low-lying spin-orbit partner of the ${}^7\mathrm{He}$ ground state does not exist. Evidence is presented that this state lies at much higher energies, in agreement with microscopic calculations.

A novel method of deducing the deformation of the $N=Z$ nucleus ${}^{76}\mathrm{Sr}$ is presented. It is based on the comparison of the experimental Gamow-Teller strength distribution $B(\mathrm{GT})$ from its $\beta$ decay with the results of quasi-random-phase approximation calculations. This method confirms previous indications of the strong prolate deformation of this nucleus in a totally independent way. The measurement has been carried out with a large total absorption gamma spectrometer, “Lucrecia,” newly installed at CERN-ISOLDE.

Charmonium production in heavy-ion collisions is investigated within a kinetic theory framework incorporating in-medium properties of open- and hidden-charm states in line with recent QCD lattice calculations. A continuously decreasing open-charm threshold across the phase boundary of hadronic and quark-gluon matter is found to have important implications for the equilibrium abundance of charmonium states. The survival of $J/\psi$ resonance states above the transition temperature enables their recreation also in the quark-gluon plasma. Including effects of chemical and thermal off-equilibrium, we compare our model results to available experimental data at CERN SPS and BNL RHIC energies. In particular, earlier found discrepancies in the ${\psi }^{\prime }/\psi$ ratio can be resolved.

Quantum phase transitions in mesoscopic systems are studied. It is shown that the main features of phase transitions, defined for infinite number of particles, $N\to \infty$, persist even for moderate $N\sim 10.$ A Landau analysis of first order transitions is done and a “critical” exponent at the spinodal point is defined. Two order parameters are introduced to distinguish first from second order transitions. Applications to atomic nuclei, molecules, atomic clusters, and finite polymers are mentioned. Experimental evidence in atomic nuclei is presented.

Data on proton-neutron bremsstrahlung have been obtained from a measurement of the quasifree breakup channel in proton-deuteron bremsstrahlung. This high-precision measurement, with an incident proton energy of 190 MeV, is fully exclusive; i.e., the protons, the neutron, and the photon have been detected. The quasifree differential cross sections obtained are compared with microscopic calculations and calculations based on soft-photon models. There are sizable differences between the models and also between the models and the data obtained for this simple process.

We show that the Dirac equation in ($3+1$) dimensions gives rise to supersymmetric patterns when the scalar and vector potentials are (i) Coulombic with arbitrary strengths or (ii) when their sum or difference is a constant, leading to relativistic pseudospin and spin symmetries. The conserved quantities and the common intertwining relation responsible for such patterns are discussed.

Mass measurements of ${}^{68}\mathrm{Ge}$, ${}^{68}\mathrm{As}$, and ${}^{68}\mathrm{Se}$ have been obtained with the Canadian Penning Trap mass spectrometer. The results determine the mass excess of ${}^{68}\mathrm{Se}$ as $-54232(19)\mathrm{keV}$, the first measurement with a precision and reliability sufficient to address the light-curve and energy output of x-ray bursts as well as the abundances of the elements synthesized. Under typical conditions used for modeling x-ray bursts, ${}^{68}\mathrm{Se}$ is found to cause a significant delay in the rp process nucleosynthesis.

We construct an effective Lagrangian which illustrates why color deconfines when chiral symmetry is restored in hot gauge theories with quarks in the fundamental representation. For quarks in the adjoint representation we show that, while deconfinement and the chiral transition do not need to coincide, entanglement between them is still present. Extension to the chemical potential driven transition is discussed.

The transverse mass spectra and midrapidity yields for $\Xi$s and $\Omega$s are presented. For the 10% most central collisions, the ${\overline{\Xi }}^{+}/h^{-}$ ratio increases from the Super Proton Synchrotron to the Relativistic Heavy Ion Collider energies while the ${\Xi }^{-}/h^{-}$ stays approximately constant. A hydrodynamically inspired model fit to the $\Xi$ spectra, which assumes a thermalized source, seems to indicate that these multistrange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to $\pi$, $K$, $p$, and $\Lambda$s.

A new experimental approach was developed that can reduce the uncertainties in astrophysical rapid proton capture ($rp$) process calculations due to nuclear data. This approach utilizes neutron removal from a radioactive ion beam to populate the nuclear states of interest. Excited states were deduced by the $\gamma$-decay spectra measured in a semiconductor Ge-detector array. In the first case studied, ${}^{33}\mathrm{Ar}$, excited states were measured with uncertainties of several keV. The 2 orders of magnitude improvement in the uncertainty of the level energies resulted in a 3 orders of magnitude improvement in the uncertainty of the calculated ${}^{32}\mathrm{Cl}(p,\gamma ){}^{33}\mathrm{Ar}$ rate that is critical to the modeling of the $rp$ process. This approach has the potential to measure key properties of almost all interesting nuclei on the $rp$-process path.

Spectra of two-step $\gamma$ cascades following the thermal ${}^{162}\mathrm{Dy}(n,\gamma ){}^{163}\mathrm{Dy}$ reaction have been measured. Distinct peaklike structures observed at the midpoints of these spectra are interpreted as a manifestation of the low-energy isovector $M1$ vibrational mode of excited ${}^{163}\mathrm{Dy}$ nuclei.

Scattering of particles produced in high energy nuclear collisions can wrestle the system into a state near local thermal equilibrium. I illustrate how measurements of the centrality dependence of the mean transverse momentum and its fluctuations can exhibit this thermalization.

The difference in the energies of the lowest states corresponding to the two nodeless single-particle orbitals outside the $Z=50$ closed proton shell, $h_{11/2}$ and $g_{7/2}$, increases with neutron excess. We have measured the Sn$(\alpha ,t)$ reaction for all seven stable even Sn isotopes and found that the spectroscopic factors are constant for these two states, confirming their characterization as single-particle states. The trend in energies is consistent with a decrease in the nuclear spin-orbit interaction. A similar trend, also suggesting a decreasing spin-orbit splitting, is seen in the energies of the neutron single-particle states outside the $N=82$ core, $i_{13/2}$ and $h_{9/2}$.

An equilateral-triangular shape of three $\alpha$ clusters surrounded by excess neutrons is suggested for ${}^{14}\mathrm{C}$, based on the molecular-orbit model. It is found that the attractive interaction between an excess neutron and an $\alpha$ particle stabilizes the $K^{\pi }=0^{+}$ and $3^{-}$ rotational bands, which demonstrates an equilateral-triangular symmetry. This $K^{\pi }=3^{-}$ band at 3 MeV below the ${}^{10}\mathrm{Be}+\alpha$ threshold energy corresponds to the experimentally observed band built on top of the second $3^{-}$ state. A positive-parity rotational band ($0^{+}$, $2^{+}$, $4^{+}$) arises similarly. These two bands suggest a molecular $3\mathrm{\text{−}}\alpha$ structure stabilized by the excess neutrons and can be viewed as a realization of the $\alpha$ crystallization in the dilute nuclear medium.

Excited states have been studied in ${}^{35}\mathrm{Ar}$ following the ${}^{16}\mathrm{O}({}^{24}\mathrm{Mg},1\alpha 1n){}^{35}\mathrm{Ar}$ fusion-evaporation reaction at 60 MeV using the Ge-detector array GASP. A comparison with the mirror nucleus ${}^{35}\mathrm{Cl}$ shows two remarkable features: (i) A surprisingly large energy difference for the $13/2^{-}$ states, in which the hitherto overlooked electromagnetic spin-orbit term is shown to play a major role, and (ii) a very different decay pattern for the $7/2^{-}$ states, which provides direct evidence of isospin mixing.

The standard and renormalized coupled cluster methods with singles, doubles, and noniterative triples and their generalizations to excited states, based on the equation of motion coupled cluster approach, are applied to the ${}^4\mathrm{He}$ and ${}^{16}\mathrm{O}$ nuclei. A comparison of coupled cluster results with the results of the exact diagonalization of the Hamiltonian in the same model space shows that the quantum chemistry inspired coupled cluster approximations provide an excellent description of ground and excited states of nuclei. The bulk of the correlation effects is obtained at the coupled cluster singles and doubles level. Triples, treated noniteratively, provide the virtually exact description.

The expansion of strongly interacting matter formed in high-energy nuclear collisions drives the system through the region of phase coexistence. The present study examines the associated spinodal instability and finds that the degree of amplification may be sufficient for the emergence of spinodal patterns that may be utilized as a diagnostic of the hadronization phase transition.

Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for $\sqrt{s_{NN}}=200\mathrm{GeV}$ $pp$ and $\mathrm{Au}+\mathrm{Au}$ collisions at Relativistic Heary Ion Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central $\mathrm{Au}+\mathrm{Au}$ collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies.

Differential cross sections for electromagnetic fission of ${}^{238}\mathrm{U}$ projectiles ($500\mathrm{MeV}/u$) in C, Sn, and Pb targets are measured and analyzed in terms of single- and multiphonon giant resonance excitations as doorway states to fission. A novel experimental method exploits the linear relationship between neutron multiplicity and the primary ${}^{238}\mathrm{U}$ excitation energy. Multiphonon states contribute up to 20% of the cross section; a component at high excitation energies is indicated that may arise from three-phonon dipole and two-phonon $\mathrm{GDR}\otimes {\mathrm{GQR}}_{iv}$ giant resonance excitations.

A Nilsson mean-field plus extended pairing interaction Hamiltonian with many-pair interaction terms is proposed. Eigenvalues of the extended pairing model are easy to obtain. Our investigation shows that one- and two-body interactions continue to dominate the dynamics for relatively small values of the pairing strength. As the strength of the pairing interaction grows, however, the three- and higher many-body interaction terms grow in importance. A numerical study of even-odd mass differences in the ${}^{154–171}\mathrm{Yb}$ isotopes shows that the extended pairing model is applicable to well deformed nuclei.