Gamma rays deexciting states in the proton emitter ${}^{145}\mathrm{Tm}$ were observed using the recoil-decay tagging method. The ${}^{145}\mathrm{Tm}$ ground-state rotational band was found to exhibit the properties expected for an $h_{11/2}$ proton decoupled band. In addition, coincidences between protons feeding the $2^{+}$ state in ${}^{144}\mathrm{Er}$ and the $2^{+}\to 0^{+}$ $\gamma$-ray transition were detected, the first measurement of this kind, leading to a more precise value for the $2^{+}$ excitation energy of 329(1) keV. Calculations with the particle-rotor model and the core quasiparticle coupling model indicate that the properties of the $\pi h_{11/2}$ band and the proton-decay rates in ${}^{145}\mathrm{Tm}$ are consistent with the presence of triaxiality with an asymmetry parameter $\gamma \approx 20°$.

The diagonal correlation energy due to $n\mathrm{\text{−}}n$, $p\mathrm{\text{−}}p$, and $n\mathrm{\text{−}}p$ pairing is shown to resolve the discrepancies between shell gaps determined from binding energy differences and the gaps calculated with Woods-Saxon potentials or with other mean-field models. The difference in diagonal correlation energy between an $N=Z$ nucleus with filled shells and the nucleus with one less nucleon resolves this problem in lowest order. A previously derived result, that the diagonal correlation energy in the last occupied orbital for the latter nuclei is $1/2$ of the equivalent correlation energy for closed shell nuclei, is tested against observed binding energies and found to be fairly accurate.

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an $800\mathrm{GeV}/c$ proton beam on a deuterium target. The muon angular distributions in the dilepton rest frame have been measured over the kinematic range $4.5<m_{\mu \mu }<15\mathrm{GeV}/c^2$, $0<p_T<4\mathrm{GeV}/c$, and $0<x_F<0.8$. No significant $\cos 2\varphi$ dependence is found in these proton-induced Drell-Yan data, in contrast with the situation for pion-induced Drell-Yan data. The data are compared with expectations from models which attribute the $\cos 2\varphi$ distribution to a QCD vacuum effect or to the presence of the transverse-momentum-dependent Boer-Mulders structure function $h_1^{\perp }$. Constraints on the magnitude of the sea-quark $h_1^{\perp }$ structure functions are obtained.

We investigated simultaneously the ${}^{12}\mathrm{C}(e,e^{\prime }p)$ and ${}^{12}\mathrm{C}(e,e^{\prime }pp)$ reactions at $Q^2=2(\mathrm{GeV}/c{)}^2$, $x_B=1.2$, and in an ($e$, $e^{\prime }p$) missing-momentum range from 300 to $600\mathrm{MeV}/c$. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For $(9.5\pm 2)\%$ of the ${}^{12}\mathrm{C}(e,e^{\prime }p)$ events, a recoiling partner proton was observed back-to-back to the ${}^{12}\mathrm{C}(e,e^{\prime }p)$ missing-momentum vector, an experimental signature of correlations.

We report on the first spectroscopy study of the very neutron-rich nucleus ${}_{12}{}^{36}\mathrm{Mg}_{24}$ using the direct two-proton knockout reaction ${}^9\mathrm{Be}({}^{38}\mathrm{Si},{}^{36}\mathrm{Mg}+\gamma )X$ at $83\mathrm{MeV}/\mathrm{\text{nucleon}}$. The energy of the first excited $2^{+}$ state of ${}^{36}\mathrm{Mg}$, $E(2_1^{+})=660(6)\mathrm{keV}$, was measured. The magnitude of the partial cross sections to the ground state and the $2_1^{+}$ state is indicative of strong intruder admixtures in the lowest-lying states as suggested by Monte Carlo shell-model calculations.

We compute energy distributions of three particles emerging from decaying many-body resonances. We reproduce the measured energy distributions from decays of two archetypal states chosen as the lowest $0^{+}$ and $1^{+}$ resonances in ${}^{12}\mathrm{C}$ populated in $\beta$ decays. These states are dominated by sequential, through the ${}^8\mathrm{Be}$ ground state, and direct decays, respectively. These decay mechanisms are reflected in the “dynamic” evolution from small, cluster or shell-model states, to large distances, where the coordinate or momentum space continuum wave functions are accurately computed.

The existence of the ${}^7\mathrm{H}$ nuclear system was investigated via a one-proton transfer reaction with a ${}^8\mathrm{He}$ beam at $15.4\mathrm{A}\mathrm{MeV}$ and a ${}^{12}\mathrm{C}$ gas target. The experimental setup was based on the active-target MAYA which allowed a complete reconstruction of the reaction kinematics. The existence of the ${}^7\mathrm{H}$ was confirmed with the identification of seven events where the system was formed with a resonance energy of ${0.57}_{-0.21}^{+0.42}\mathrm{MeV}$ above the ${}^3\mathrm{H}+4n$ threshold and a resonance width of ${0.09}_{-0.06}^{+0.94}\mathrm{MeV}$. This study represents an unambiguous proof of the existence of the most neutron-proton unbalanced system presently found.

A beyond-mean-field theory of new generation has been developed and applied for the first time to discuss the controversial $N=32$ and/or $N=34$ shell closures and the puzzling behavior of the transition probabilities from the ground to the first $2^{+}$ state in the titanium isotopes. In the numerical applications, the finite range density dependent Gogny interaction has been used. As compared with the experimental data for several calcium, titanium, and chromium isotopes, we obtain a good agreement for the excitation energies and a reasonable one for the transition probabilities. Our calculations support a shell closure for $N=32$ but not for $N=34$.

A new measurement of the $\beta$-delayed $\alpha$ decay of ${}^{16}\mathrm{N}$ has been performed using a set of high efficiency ionization chambers. Sources were made by implantation of a ${}^{16}\mathrm{N}$ beam, yielding very clean $\alpha$ spectra down to energies as low as 400 keV. Our data are in good agreement with earlier results. For the $S$ factor $S_{E1}$, we obtain a value of $74\pm 21\mathrm{keV}\mathrm{b}$. In spite of improvements in the measurement, the error in $S_{E1}$ remains relatively large because of the correlations among the fit parameters and the uncertainties inherent to the extrapolation.

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a ${}^{12}\mathrm{C}$ target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed ${}_{\Lambda }{}^{12}\mathrm{B}$ spectrum shows for the first time identifiable strength in the core-excited region between the ground-state $s$-wave $\Lambda$ peak and the 11 MeV $p$-wave $\Lambda$ peak.

Differential elliptic flow ($v_2$) for $\varphi$ mesons and (anti)deuterons $(\overline{d})d$ is measured for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The $v_2$ for $\varphi$ mesons follows the trend of lighter ${\pi }^{\pm }$ and $K^{\pm }$ mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The $v_2$ values for $(\overline{d})d$ suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of $v_2$ per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.

Transition rate measurements are reported for the $2_1^{+}$ and $2_2^{+}$ states in $N=Z$ ${}^{64}\mathrm{Ge}$. The experimental results are in excellent agreement with large-scale shell-model calculations applying the recently developed GXPF1A interactions. The measurement was done using the recoil distance method (RDM) and a unique combination of state-of-the-art instruments at the National Superconducting Cyclotron Laboratory (NSCL). States of interest were populated via an intermediate-energy single-neutron knockout reaction. RDM studies of knockout and fragmentation reaction products hold the promise of reaching far from stability and providing lifetime information for excited states in a wide range of nuclei.

The nearside distribution of particles at intermediate transverse momentum, associated with a high momentum trigger hadron produced in a high energy heavy-ion collision, is broadened in rapidity compared with the jet cone. This broadened distribution is thought to contain the energy lost by the progenitor parton of the trigger hadron. We show that the broadening can be explained as the final-state deflection of the gluons radiated from the hard parton inside the medium by soft, transversely oriented, turbulent color fields that arise in the presence of plasma instabilities. The magnitude of the effect is found to grow with medium size and density and diminish with increasing energy of the associated hadron.

Properties of finite nuclei are evaluated with two-nucleon ($NN$) and three-nucleon ($NNN$) interactions derived within chiral effective field theory. The nuclear Hamiltonian is fixed by properties of the $A=2$ system, except for two low-energy constants (LECs) that parametrize the short range $NNN$ interaction, which we constrain with the $A=3$ binding energies. We investigate the sensitivity of ${}^4\mathrm{He}$, ${}^6\mathrm{Li}$, ${}^{10,11}\mathrm{B}$, and ${}^{12,13}\mathrm{C}$ properties to the variation of the constrained LECs. We identify observables that are sensitive to this variation and find preferred values that give the best overall description. We demonstrate that the $NNN$ interaction terms significantly improve the binding energies and spectra of mid-$p$-shell nuclei not just with the preferred choice of the LECs but even within a wide range of the constrained LECs. We find that a very high quality description of these nuclei requires further improvements to the chiral Hamiltonian.

The shape isomer in ${}^{235}\mathrm{U}$ has been searched for in a neutron-induced fission experiment on ${}^{234}\mathrm{U}$, which was performed at the isomer spectrometer NEPTUNE of the EC-JRC IRMM. A neutron source, with a tunable pulse frequency in the Hz to kHz range and its individually adjustable neutron pulse width in connection with an appropriate detector system turned out to be the ideal instrument to perform an isomer search, when decay half-lives above $100\mu \mathrm{s}$ are expected. From the delayed fission events observed for two different NEPTUNE settings and at mean incident neutron energies $E_n=0.95$ and 1.27 MeV the isomeric fission half-life could be determined to be $T_{1/2}=(3.6\pm 1.8)\mathrm{ms}$. The corresponding cross section was determined to ${\sigma }_{if}=(10\pm 8)\mu \mathrm{b}$. With these results an experimental confirmation for the existence of a superdeformed shape isomer in odd-uranium isotopes is given for the first time.

We report on a novel experimental approach for studying the dissipative spreading of collective motion in a metastable nuclear system, using, for the first time, highly fissile nuclei with spherical shape. This was achieved by fragmentation of 45 radioactive heavy-ion beams at GSI, Darmstadt. The use of inverse kinematics and a dedicated experimental setup allowed for the identification in atomic number of both fission fragments. From the width of their nuclear-charge distributions, a transient time of $(3.3\pm 0.7)\times {10}^{-21}\mathrm{s}$ is deduced for initially spherical nuclei.

We report the first comprehensive calculations of $2^{+}$ excitations with a microscopic theory applicable to over 90% of the known nuclei. The theory uses a quantal collective Hamiltonian in five dimensions. The only parameters in theory are those of the finite-range, density-dependent Gogny D1S interaction. The following properties of the lowest $2^{+}$ excitations are calculated: excitation energy, reduced transition probability, and spectroscopic quadrupole moment. We find that the theory is very reliable to classify the nuclei by shape. For deformed nuclei, average excitation energies and transition quadrupole moments are within 5% of the experimental values, and the dispersion about the averages are roughly 20% and 10%, respectively. Including all nuclei in the performance evaluation, the average transition quadrupole moment is 11% too high and the average energy is 13% too high.

The exact solution of the proton-neutron isoscalar-isovector ($T=0,1$) pairing Hamiltonian with nondegenerate single-particle orbits and equal pairing strengths is presented for the first time. The Hamiltonian is a particular case of a family of integrable SO(8) Richardson-Gaudin models. The exact solution of the $T=0,1$ pairing Hamiltonian is reduced to a problem of 4 sets of coupled nonlinear equations that determine the spectral parameters of the complete set of eigenstates. The microscopic structure of individual eigenstates is analyzed in terms of evolution of the spectral parameters in the complex plane for a system of $A=80$ nucleons. The spectroscopic trends of the exact solutions are discussed in terms of generalized rotations in isospace.

A high-statistics measurement of bremsstrahlung emitted in the $\alpha$ decay of ${}^{210}\mathrm{Po}$ has been performed, which allows us to follow the photon spectra up to energies of $\sim 500\mathrm{keV}$. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasiclassical approximation as well as with the exact quantum mechanical calculation. It is shown that, due to the small effective electric dipole charge of the radiating system, a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the $\alpha$ particle and the emitted photon.

We investigate the spatial structure of the two-neutron wave function in the Borromean nucleus ${}^{11}\mathrm{Li}$, using a three-body model of ${}^9\mathrm{Li}+n+n$, which includes many-body correlations stemming from the Pauli principle. The behavior of the neutron pair at different densities is simulated by calculating the two-neutron wave function at several distances between the core nucleus ${}^9\mathrm{Li}$ and the center of mass of the two neutrons. With this representation, a strong concentration of the neutron pair on the nuclear surface is for the first time quantitatively established for neutron-rich nuclei. That is, the neutron pair wave function in ${}^{11}\mathrm{Li}$ has an oscillatory behavior at normal density, while it becomes a well-localized single peak in the dilute density region around the nuclear surface. We point out that these features qualitatively correspond to the BCS- and BEC-like structures of the pair wave function found in infinite nuclear matter.