We present results on the electroexcitation of the low mass resonances $\Delta (1232)P_{33}$, $N(1440)P_{11}$, $N(1520)D_{13}$, and $N(1535)S_{11}$ in a wide range of $Q^2$. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for $\pi$ electroproduction off the proton. The data were analyzed using two conceptually different approaches—fixed-$t$ dispersion relations and a unitary isobar model—allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the $\Delta (1232)P_{33}$ show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for $Q^2⩽6$ GeV${}^2$. For the Roper resonance, $N(1440)P_{11}$, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark ($3q$) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the $N(1535)S_{11}$ allowed us to obtain the branching ratios of this state to the $\pi N$ and $\eta N$ channels via comparison with the results extracted from $\eta$ electroproduction. The extensive CLAS data also enabled the extraction of the ${\gamma }^{*}p\to N(1520)D_{13}$ and $N(1535)S_{11}$ longitudinal helicity amplitudes with good precision. For the $N(1535)S_{11}$, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a $3q$ excitation. The transverse amplitudes for the $N(1520)D_{13}$ clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at $Q^2>1$ GeV${}^2$, confirming a long-standing prediction of the constituent quark model.

The $g$ factor of the $2_1^{+}$ state of ${}^{172}\mathrm{Hf}$ was measured using the perturbed angular correlation technique in a static external magnetic field. The result, $g(2_1^{+})=0.25(5)$, is discussed in relation to the systematics of the previously reported $g$ factors in the Hf isotopes and compared with the predictions of several models. An interesting outcome of the analysis presented in this paper is the agreement between the calculated $g$ factors within the interacting boson approximation (IBA) and the results of a large-scale shell model calculation. This agreement supports the emphasis in the IBA on the valence space. The undershooting of the empirical $g$ factors near midshell in both models suggests that they underestimate the role of the saturation of collectivity, which is explicitly incorporated into a phenomenological model that agrees better with the data.

Masses of the radionuclides ${}^{32,33}\mathrm{Si}$ and ${}^{34}\mathrm{P}$ and of the stable nuclides ${}^{32}\mathrm{S}$ and ${}^{31}\mathrm{P}$ have been measured with the Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer. Relative mass uncertainties as low as $3\times {10}^{-9}$ have been achieved. The measured mass value of ${}^{32}\mathrm{Si}$ differs from the literature value by four standard deviations. The precise mass determination of ${}^{32}\mathrm{Si}$ and ${}^{32}\mathrm{S}$ have been employed to test the validity of the quadratic form of the isobaric multiplet mass equation (IMME) for the most well known $A=32$, $T=2$ isospin quintet. The new experimental results indicate a dramatic breakdown of the model.

We show that the event-by-event fluctuations of the transverse size of the initial source, which follow directly from the Glauber treatment of the earliest stage of relativistic heavy-ion collisions, cause, after hydrodynamic evolution, fluctuations of the transverse flow velocity at hadronic freeze-out. This, in turn, leads to event-by-event fluctuations of the average transverse momentum, $\langle p_T\rangle$. Simulations with GLISSANDO for the Glauber phase, followed by a realistic hydrodynamic evolution and statistical hadronization carried out with THERMINATOR, lead to agreement with the Relativistic Heavy Ion Collider (RHIC) data. In particular, the magnitude of the effect, its centrality dependence, and the weak dependence on the incident energy are properly reproduced. Our results show that the bulk of the observed event-by-event $\langle p_T\rangle$ fluctuations may be explained by the fluctuations of the size of the initial source.

We perform a fully relativistic calculation of the ${}^2\overrightarrow{\mathrm{H}}(e,e^{\text{'}}p)n$ reaction in the impulse approximation employing the Gross equation to describe the deuteron ground state, and we use the SAID parametrization of the full $\mathit{NN}$ scattering amplitude to describe the final state interactions (FSIs). The formalism for treating target polarization with arbitrary polarization axes is discussed, and general properties of some asymmetries are derived from it. We show results for momentum distributions and angular distributions of various asymmetries that can only be accessed with polarized targets.

We investigate baryon transport in relativistic heavy-ion collisions at energies reached at the CERN Super Proton Synchrotron (SPS), BNL Relativistic Heavy-Ion Collider (RHIC), and CERN’s Large Hadron Collider (LHC) in the model of saturation. An analytical scaling law is derived within the color glass condensate framework based on small-coupling QCD. Transverse momentum spectra, net-baryon rapidity distributions, and their energy, mass, and centrality dependencies are well described. In comparison with RHIC data in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=62.4$ and $200$ GeV, the gradual approach to the gluon saturation regime is investigated and limits for the saturation-scale exponent are determined. Predictions for net-baryon rapidity spectra and the mean rapidity loss in central $\mathrm{Pb}+\mathrm{Pb}$ collisions at LHC energies of $\sqrt{s_{\mathit{NN}}}=5.52$ TeV are made.

Isobarically purified beams of ${}^{77}\mathrm{Cu}$ with energies of $225$ and $0.2$ MeV were used at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory to study $\beta$ decay into states in ${}^{77}\mathrm{Zn}$. Data taken at $225$ MeV allowed the determination of absolute branching ratios relative to the decay of ${}^{77}\mathrm{Cu}$ for this $\beta$ decay as well as its daughters. From these we obtained a refined $\beta$-delayed neutron emission probability of $30.3(22)\%$ and a probability that the decay proceeds through ${}^{77}\mathrm{Zn}$${}^g$ of $49.1(26)\%$. A total of $64\hspace{0.5em}\gamma$ rays were placed in a level scheme for ${}^{77}\mathrm{Zn}$ containing $35$ excited states including one state above the neutron separation energy, whereas two $\gamma$ rays were observed for the $\beta$$n$ branch to states in ${}^{76}\mathrm{Zn}$. The growth and decay curves of some prominent $\gamma$ rays indicate a single $\beta$-decaying state with a half-life of $480(9)\hspace{0.5em}$ms. The decay pattern for ${}^{77}\mathrm{Cu}$, with observed feeding of $8(3)\%$ to $7/2^{+}\hspace{0.5em}$${}^{77}\mathrm{Zn}$${}^g$ and $6(3)\%$ to $1/2^{-}\hspace{0.5em}$${}^{77}\mathrm{Zn}$${}^m$, in contrast to the large feeding observed for decay of $\pi p_{3/2}$ ${}^{73}\mathrm{Cu}$${}^g$ to $1/2^{-}\hspace{0.5em}$${}^{73}\mathrm{Zn}$${}^g$, strongly suggests a $\pi f_{5/2}$ ground state for the studied ${}^{77}\mathrm{Cu}$ activity.

I study the nuclear structure function $F_2^A$ and its logarithmic derivative in the high-energy limit (small-$x$ region) using the color glass condensate formalism. In this limit the structure function $F_2$ depends on the quark-antiquark dipole-target scattering cross section $N_F(x_{\mathit{bj}},r_t,b_t)$. The same dipole cross section appears in single-hadron and hadron-photon production cross sections in the forward rapidity region in deuteron (proton)-nucleus collisions at high energy, that is, at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). I use a parametrization of the dipole cross section, which has successfully been used to describe the deuteron-gold data at the RHIC, to compute the nuclear structure function $F_2^A$ and its log $Q^2$ derivative (which is related to gluon distribution function in the double log limit). I provide a quantitative estimate of the nuclear shadowing of $F_2^A$ and the gluon distribution function in the kinematic region relevant to a future electron-ion collider.

With the advent of new photon-tagging facilities and novel experimental technologies, it has become possible to perform photoproduction cross-sectional measurements of pseudoscalar mesons on nuclei with percent-level accuracy. The extraction of the radiative decay widths from these measurements at forward angles is done by the Primakoff method, which requires theoretical treatment of all processes participating in these reactions at the same percent level. In this work, we review the theoretical approach to meson photoproduction amplitudes in the electromagnetic and strong fields of nuclei at forward angles. The most updated description of these processes are presented based on the Glauber theory of multiple scattering. In particular, the effects of final-state interactions, corrections for light nuclei, and photon shadowing in nuclei are discussed.

Total and differential cross sections for $\eta$ and ${\eta }^{\text{'}}$photoproduction off the proton have been determined with the CBELSA/TAPS detector for photon energies between $0.85$ and $2.55$ GeV. The $\eta$ mesons are detected in their two neutral decay modes, $\eta \to \gamma \gamma$ and $\eta \to 3{\pi }^0\to 6\gamma$, and for the first time, cover the full angular range in $\cos \hspace{0.5em}{\theta }_{c.m.}$ of the $\eta$ meson. These new $\eta$ photoproduction data are consistent with the earlier CB-ELSA results. The ${\eta }^{\text{'}}$ mesons are observed in their neutral decay to ${\pi }^0{\pi }^0\eta \to 6\gamma$ and also extend the coverage in angular range.

Initial eccentricity and eccentricity fluctuations of the interaction volume created in relativistic collisions of deformed ${}^{197}\mathrm{Au}$ and ${}^{238}\mathrm{U}$ nuclei are studied using optical and Monte Carlo (MC) Glauber simulations. It is found that the nonsphericity noticeably influences the average eccentricity in central collisions, and eccentricity fluctuations are enhanced from deformation. Quantitative results are obtained for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{U}+\mathrm{U}$ collisions at energy $\sqrt{s_{\mathit{NN}}}=200$ GeV.

The extraction of the nuclear incompressibility from isoscalar giant monopole resonance (GMR) measurements is analyzed. Pairing may play a role in the shift of the GMR energy between the doubly closed shell ${}^{208}\mathrm{Pb}$ nucleus and other Pb isotopes. Pairing effects are predicted microscopically using the constrained Hartree-Fock-Bogoliubov method. Accurate measurements of the GMR in open-shell Pb isotopes are necessary.

We employ the Gamow shell model (GSM) to describe low-lying states of the oxygen isotopes ${}^{24}\mathrm{O}$ and ${}^{25}\mathrm{O}$. The many-body Schrödinger equation is solved starting from a two-body Hamiltonian defined by a renormalized low-momentum nucleon-nucleon ($\mathit{NN}$) interaction and a spherical Berggren basis. The Berggren basis treats bound, resonant, and continuum states on an equal footing and is therefore an appropriate representation of loosely bound and unbound nuclear states near threshold. We show that the inclusion of continuum effects has a significant effect on the low-lying $1^{+}$ and $2^{+}$ excited states in ${}^{24}\mathrm{O}$. On the other hand, we find that a correct description of binding energy systematics of the ground states is driven by the proper treatment and inclusion of many-body correlation effects. This is supported by the fact that we get ${}^{25}\mathrm{O}$ unstable with respect to ${}^{24}\mathrm{O}$ in both oscillator and Berggren representations starting from a ${}^{22}\mathrm{O}$ core. Furthermore, we show that the structure of these loosely bound or unbound isotopes is strongly influenced by the ${}^1{S}_0$ component of the $\mathit{NN}$ interaction. This has important consequences for our understanding of nuclear stability.

The emission of two protons, a highly exotic decay process, has been reported from the high-spin ${21}^{+}$ isomer in ${}^{94}\mathrm{Ag}$ [I. Mukha et al., Nature (London) 439, 298 (2006)]. Recent experimental results from $\gamma$-ray spectroscopy and Penning trap mass measurements, as well as theoretical predictions, are difficult to reconcile with this claim. These anomalies motivate a closer look at the supporting evidence. A detailed review of this evidence suggests that is it unsafe to conclude that the methods used in the two-proton identification experiment demonstrate an “unambiguous signature” for two-proton emission. Because the apparatus used could not distinguish protons from positrons and electrons, the identification stands or falls on coincidences with $\gamma$ rays in the daughter nucleus ${}^{92}\mathrm{Rh}$. It is shown that spurious peaks from Compton-scattered $\gamma$ rays associated with the dominant background from ${}^{94}\mathrm{Ag}$ $\beta$ decay could have been misidentified as ${}^{92}\mathrm{Rh}$ $\gamma$ rays.

We calculate the lowest-order charm and beauty parton distribution functions in and fragmentation functions into $D$ and $B$ mesons using the operator definitions of factorized perturbative quantum chromodynamics (QCD). In the vacuum, we find the leading corrections that arise from the structure of the final-state hadrons. Quark-antiquark potentials extracted from the lattice are employed to demonstrate the existence of open heavy flavor bound-state solutions in the quark-gluon plasma in the vicinity of the critical temperature. We provide first results for the in-medium modification of the heavy-quark distribution and decay probabilities in a comoving plasma. In an improved perturbative QCD description of heavy-flavor dynamics in the thermal medium, we combine $D$- and $B$-meson formation and dissociation with parton-level charm and beauty quark quenching to obtain predictions for the heavy-meson and nonphotonic-electron suppression in $\mathrm{Cu}+\mathrm{Cu}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider, respectively.

Within the framework of the dinuclear system (DNS) model, production cross sections of new superheavy nuclei with charged numbers $Z=108–114$ are analyzed systematically. Possible combinations based on the actinide nuclides ${}^{238}\mathrm{U}$, ${}^{244}\mathrm{Pu}$, and ${}^{248,250}\mathrm{Cm}$ with the optimal excitation energies and evaporation channels are pointed out to synthesize new isotopes that lie between the nuclides produced in the cold fusion reactions and the ${}^{48}\mathrm{Ca}$-induced fusion reactions experimentally, which are feasible to be constructed experimentally. It is found that the production cross sections of superheavy nuclei decrease drastically with the charged numbers of compound nuclei. Larger mass asymmetries of the entrance channels enhance the cross sections in $2n–5n$ channels.

Suppression measurements for neutral pions (${\pi }^0$) are used to investigate the predicted path length $L$ and transverse momentum $p_T$ dependent jet quenching patterns of the hot QCD medium produced in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV. The observed scaling patterns show the predicted trends for jet-medium interactions dominated by radiative energy loss. They also allow simple estimates of the transport coefficient $\widehat{q}$ and the ratio of viscosity to entropy density $\eta /s$. These estimates indicate that the short mean free path $\lambda$ in the QCD medium leading to hydrodynamic-like flow with a small value of $\eta /s$ is also responsible for the strong suppression observed.

The transient-field technique has been used to measure, with considerably improved precision, the $g$ factors of the $3/2^{+}$ and $5/2^{+}$ states in ${}^{125}\mathrm{Te}$ at 444 and 463 keV, respectively, relative to the $g$ factor of the first excited state in ${}^{126}\mathrm{Te}$. Together with shell model and weak-coupling core-excitation model calculations, the $g$-factor measurements provide insight into the orbital occupation of the odd neutron for the low-excitation states in ${}^{125}\mathrm{Te}$. A new $9/2^{+}$ level at 1029 keV, together with a firm $7/2^{+}$ spin assignment for the level at 1018 keV, identifies candidate states for the coupling of the $s_{1/2}$ neutron to the $4^{+}$ core excitation.