We derive local microscopic optical potentials $U$ systematically for polarized proton scattering at 65 MeV using the local-potential version of the Melbourne $g$-matrix folding model. As target nuclei, we take ${}^6$He and neutron-rich Ne isotopes in addition to stable nuclei of mass number $A=4$–208 in order to clarify mass-number and isotope dependence of $U$. The local potentials reproduce the experimental data systematically and have geometries similar to the phenomenological optical potentials for stable targets. The target density is broadened by the weak-binding nature and/or deformation of unstable nuclei. For the real spin-orbit part of $U$ the density broadening weakens the strength and enlarges the radius, whereas for the central part it enlarges both of the strength and the radius. The density-broadening effect is conspicuous for halo nuclei such as ${}^6$He and ${}^{31}$Ne. Similar discussions are made briefly for proton scattering at 200 MeV. We briefly investigate how the isovector and the nonspherical components of $U$ affect proton scattering.

We present various cases where the coupling of breakup or transfer channels to the elastic channel leads to an increase in the elastic channel $|S_L|$  for particular values of $L$. Particular emphasis is given to ${}^6$Li, ${}^7$Be, and ${}^8$B scattering from ${}^{58}$Ni and ${}^6$He scattering from ${}^{208}$Pb, all near the Coulomb barrier. A link is proposed to the fact that ${}^8$B has a larger breakup cross section while its elastic scattering angular distribution is less modified by breakup than ${}^6$Li and ${}^7$Be at the same energy relative to the barrier; an argument is made relating this to non-local processes. We also describe cases of ${}^6$He scattering from ${}^{208}$Pb at energies far above the Coulomb barrier, of heavy ion scattering, and of ${}^2$H and ${}^3$He scattering. The effect is absent in otherwise similar proton scattering cases. The increase in $|S_L|$ is associated with strongly absorptive potentials and excitation processes that keep an excited amplitude of the projectile from the absorptive region prior to de-excitation to the elastic channel. The possible relevance to direct reactions is proposed.

We discuss theoretical issues pertaining to baryonic matter in the combined heavy-quark and large $N_c$ limits of QCD. Witten's classic argument that baryons and interacting systems of baryons can be described in a mean-field approximation with each of the quarks moving in an average potential due to the remaining quarks is heuristic. It is important to justify this heuristic description for the case of baryonic matter since systems of interacting baryons are intrinsically more complicated than single baryons due to the possibility of hidden color states—states in which the subsystems making up the entire baryon crystal are not color-singlet nucleons but rather colorful states coupled together to make a color-singlet state. In this work, we provide a formal justification of this heuristic prescription. In order to do this, we start by taking the heavy quark limit, thus effectively reducing the problem to a many-body quantum mechanical system. This problem can be formulated in terms of integrals over coherent states, which for this problem are simple Slater determinants. We show that for the many-body problem, the support region for these integrals becomes narrow at large $N_c$, yielding an energy which is well approximated by a single coherent state—that is a mean-field description. Corrections to the energy are of relative order $1/N_c$. While hidden color states are present in the exact state of the heavy quark system, they only influence the interaction energy below leading order in $1/N_c$.

The strong magnetic fields found on the surface of magnetars are known to have profound effects on the physics of atoms in magnetar envelopes. We argue that the Friedel oscillations in the Coulomb force between the ions due to electron shielding can, for certain values of the parameters, be the dominant effect determining the crystal structure in the outer crust of magnetars. We estimate the densities and magnetic fields for which this occurs and compute some of the elastic moduli and lattice phonon dispersion relations in this “Friedel-crystal” phase.

In this work we investigate different possible interpretations of the $\Lambda \left(1405\right)$ signal associated with the production of the $\Lambda \left(1405\right)$ in $p+p$ reactions at 3.5 GeV beam kinetic energy measured by the HADES collaboration. We study the influence of interference effects between the $\Lambda \left(1405\right)$ resonance and the nonresonant background. The two poles nature of the $\Lambda \left(1405\right)$, which is supported by most of the theoretical models, is also discussed with emphasis on the relative contributions of the two complex poles to the formation of the resonance in $p+p$ reactions.

Measurements of nonyrast electric quadrupole moments (i.e., diagonal $E2$ matrix elements) of atomic nuclei are becoming widely available from multiple-step Coulomb excitation. It is shown that, where quadrupole-moment data exist, $\langle 2_1^{+}\left|\right|E2\left|\right|2_1^{+}\rangle +\langle 2_2^{+}\left|\right|E2\left|\right|2_2^{+}\rangle \approx 0$ is observed across a wide range of masses, deformations, and first $2^{+}$ energies. Nearly all of these quadrupole-moment data, particularly $\langle 2_2^{+}\left|\right|E2\left|\right|2_2^{+}\rangle$, are from the past two decades with half of the data from the past decade. In addition, $\langle 4_1^{+}\left|\right|E2\left|\right|4_1^{+}\rangle +\langle 4_2^{+}\left|\right|E2\left|\right|4_2^{+}\rangle +\langle 4_3^{+}\left|\right|E2\left|\right|4_3^{+}\rangle \approx 0$ is observed within two standard deviations for three of the four existing measurements. Despite many and varying complexities in the structure details of the individual nuclei, the correlations in the quadrupole moments appear simple.

Candidates for three excited states in the ${}^{66}$Se have been identified using the recoil-$\beta$ tagging method together with a veto detector for charged-particle evaporation channels. These results allow a comparison of mirror and triplet energy differences between analog states across the $\mathit{\text{A}}=66$ triplet as a function of angular momentum. The extracted triplet energy differences follow the negative trend observed in the $f_{7/2}$ shell. Shell-model calculations indicate that the strength of the Coulomb isotensor part alone is not sufficient to account for this trend in the case of the $\mathit{\text{A}}=66$ triplet.

We report Green's function Monte Carlo calculations of isospin-mixing (IM) matrix elements for the $2^{+}$, $1^{+}$, and $3^{+}$ $T=0$ and 1 pairs of states at 16–19 MeV excitation in ${}^8$Be. The realistic Argonne $v_{18}$ (AV18) two-nucleon and Illinois-7 three-nucleon potentials are used to generate the nuclear wave functions. Contributions from the full electromagnetic interaction and strong class III charge-symmetry breaking (CSB) components of the AV18 potential are evaluated. We also examine two theoretically more complete CSB potentials based on $\rho$-$\omega$ mixing, tuned to give the same neutron-neutron scattering length as AV18. The contribution of these different CSB potentials to the ${}^3$H-${}^3$He, ${}^7$Li-${}^7$Be, and ${}^8$Li-${}^8$B isovector energy differences is evaluated and reasonable agreement with experiment is obtained. Finally, for the ${}^8$Be IM calculation we add the small class IV CSB terms coming from one-photon, one-pion, and one-$\rho$ exchange, as well as $\rho$-$\omega$ mixing. The expectation values of the three CSB models vary by up to 20% in the isovector energy differences, but only by 10% or less in the IM matrix element. The total matrix element gives 85–90% of the experimental IM value of $-145$ keV for the $2^{+}$ doublet, with about two thirds coming from the Coulomb interaction. We also report the IM matrix element to the first $2^{+}$ state at 3 MeV excitation, which is the final state for various tests of the standard model for $\beta$ decay.

Background: Single-particle and collective modes of nuclear excitation compete in the isotopes of the elements ${}_{30}$Zn, ${}_{32}$Ge, ${}_{34}$Se, ${}_{36}$Kr, and ${}_{38}$Sr.

Purpose: To study the factors which determine the onset of collectivity in this region.

Methods: Data obtained from National Nuclear Data Center compilations supplemented by recent measurements of excitation energies and $B\left(E2\right)$ reduced transition probabilities between the low-lying states in these elements were examined. The data were analyzed as a function of the neutron number $N$ as well as the parameter $P=N_p{N}_n/(N_p+N_n)$ related to the number of valence protons and neutrons, $N_p$ and $N_n$, in the $28\le Z,N\le 50$ shell.

Results: The systematics of the data show variations ranging from mostly single-particle to collective excitations.

Conclusions: Collectivity sets in when the number of both protons and neutrons lie near the middle of the shell $30\le Z,N\le 50$. Backbends appear in the data showing that particles and holes in the major shell behave differently. The $2_2^{+}$ states exhibit single particle behavior. The transition probabilities of the $2_2^{+}$ states in the Kr isotopes differ significantly from the systematics.

High-spin states in ${}^{122}$Te were populated in the reaction ${}^{82}$Se(${}^{48}$Ca, ${\alpha 4n)}^{122}$Te at a beam energy of 200 MeV and $\gamma$-ray coincidences were measured with the Gammasphere spectrometer. The previously known level scheme was extended to considerably higher spin. Maximally aligned states and several high-energy transitions feeding into some of these levels were observed. In addition, seven collective high-spin bands were discovered for the first time in this nucleus. The experimental results are compared with cranked Nilsson-Strutinsky model calculations and possible configuration assignments to the new high-spin structures are discussed.

In recent years it has become conventional practice to include higher-order cylindrical harmonics in the phenomenological description of two-particle angular correlations from ultra-relativistic heavy-ion collisions. These model elements, whose dependence on relative azimuth angle has the form $\cos \left[m({\varphi }_1-{\varphi }_2)\right]$, where $m>2$, were introduced to support a hydrodynamic flow interpretation of the same-side ($|{\varphi }_1-{\varphi }_2|<\pi /2$) two-dimensional (2D) peak in the correlations. Previous studies have shown that the $m>2$ harmonics are not required by the data, that they destabilize the fitting models, and that their net effect is to decompose the same-side peak into two components, one being dependent on and the other being independent of relative pseudorapidity. Thus, we are led to question whether descriptions of angular correlation data including higher-order harmonics inform our understanding of the same-side peak or heavy-ion collisions in general. Results from analysis of two-dimensional angular correlation data from the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider show that the RHIC data do not exclude a single-Gaussian hypothesis for the same-side peak. We find that the net effect of including the $m=3$ harmonic or azimuth sextupole in the fitting model is the inclusion of small non-Gaussian dependence in the mathematical description of the same-side peak. Those non-Gaussian effects are systematically insignificant and can be accommodated by minor perturbations to the same-side 2D Gaussian peak model, which act locally at small relative azimuth. We also demonstrate that the 0%–1% 2D angular correlation data for 2.76-TeV $\text{Pb}+\text{Pb}$ collisions from ATLAS, which display an away-side double peak on azimuth, do not require a sextupole, and exclude a positive same-side sextupole.

We calculate the shear $\eta \left(T\right)$ and bulk viscosities $\zeta \left(T\right)$ as well as the electric conductivity ${\sigma }_e\left(T\right)$ and heat conductivity $\kappa \left(T\right)$ within the Nambu–Jona-Lasinio model for three flavors as a function of temperature as well as the entropy density $s\left(T\right)$, pressure $P\left(T\right)$, and speed of sound $c_s^2\left(T\right)$. We compare the results with other models such as the Polyakov–Nambu–Jona-Lasinio (PNJL) model and the dynamical quasiparticle model (DQPM) and confront these results with lattice QCD data whenever available. We find the NJL model to have a limited predictive power for the thermodynamic variables and various transport coefficients above the critical temperature, whereas the PNJL model and DQPM show acceptable results for the quantities of interest.

We investigate near-threshold production of quarkonium resonances in cold nuclear matter through a phenomenologically motivated scaling theory with two exponents, which are fixed by existing data on near-threshold $J/\psi$ production in proton-nucleus collisions. Interestingly, it seems possible to extend one of the exponents to the production of other mesons in cold nuclear matter. The scaling theory can be tested and refined in experiments at the upcoming high-intensity Facility for Antiproton and Ion Research (FAIR) accelerator complex at GSI.

The low-lying level schemes and electromagnetic transitions of ${}^{109}$Te, ${}^{109}$I, and the neighboring even-even nucleus ${}^{108}$Te are calculated within the framework of the $SD$-pair approximation of the nuclear shell model. Good agreement is obtained between the calculated results and experimental data. The favored components of low-lying bands are discussed in the collective nucleon-pair subspace. The weak-coupling picture shown in these nuclei and its relationship with residual quadrupole-quadrupole interaction between valence protons and neutrons are analyzed.

We investigate the applicability of a random-matrix model to the description of noncollective excitations in heavy-ion reactions around the Coulomb barrier. To this end, we study fusion in the reaction ${}^{16}$O + ${}^{208}$Pb, taking account of the known noncollective excitations in the ${}^{208}$Pb nucleus. We show that the random-matrix model for the corresponding couplings reproduces reasonably well the exact calculations, obtained using empirical deformation parameters. This implies that the model may provide a powerful method for systems in which the noncollective couplings are not so well known.

We investigate the possibility of selecting heavy ion collision events with certain features in the initial state (event engineering). Anisotropic flow measurements in heavy ion reactions have confirmed the almost ideal fluid dynamical behavior of the hot and dense quark-gluon plasma state. As a consequence, it is intriguing to pursue the idea of selecting collisions with a certain special initial geometry, e.g., a large ellipsoidal or triangular deformation, by classifying events by the value of their final observed flow coefficients. This procedure could be especially interesting for azimuthally dependent jet energy loss studies. We investigate the correlation between initial state features and final state momentum space anisotropies within an event-by-event hybrid approach. We find that the finite particle number and hadronic rescattering of the final state leads to large event-by-event fluctuations in the observables that could be used to characterize the features of the initial state. This makes event engineering by final state selection difficult.

In the study of hadron production in Au-Au collisions at the BNL Relativistic Heavy-Ion Collider (RHIC), minijets play an important role in generating shower partons in the intermediate $p_T$ region. Momentum degradation of the hard and semihard partons as they traverse the inhomogeneous medium at various azimuthal angles results in a complicated convolution of geometrical, nuclear, and dynamical factors that cannot usually be described in a transparent way. In this work a compact formula is found that represents the inclusive distributions of minijets of any parton type at the surface of the medium for any collision centrality. They take into account the contributions from all initiating partons created at any point in the medium. By comparing with the case of no energy loss, a ratio has been determined that is analogous to the nuclear modification factor for minijets. Phenomenological reality of such distributions is examined by calculating the hadronization of the minijets in the recombination model. Good fits of the data on pion, kaon and proton production throughout the intermediate $p_T$ region have been obtained by adjusting the parameters controlling the magnitude of the thermal partons and the degradation rates of the semihard partons. The result gives support to the minijet spectra at any centrality on the one hand, and the hadronization procedure used on the other. An important property made manifest in this study is that quarks and gluons must not lose energy in the same way because the partons form mesons and baryons differently by recombination and the momenta of quarks and gluons must be degraded at different rates in order to reproduce the experimental pion and proton spectra. This is a feature that renders invalid the notion of parton-hadron duality or other hadronization schemes based on similar ideas.

The low-lying dipole strength of the open-shell nucleus ${}^{94}$Mo was studied via the nuclear resonance fluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity $\gamma$-ray Source (HI$\gamma$S) facility. In total, 83 excited states were identified. Exploiting polarized quasi-monoenergetic photons at HI$\gamma$S, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HI$\gamma$S measurements at five energy settings. Mean branching ratios to the ground state and first excited $2_1^{+}$ state were extracted from the measurements with quasi-monoenergetic photons and compared to $\gamma$-cascade simulations within the statistical model. The experimentally deduced mean branching ratios exhibit a resonance-like maximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.

The bound states of ${}^{12}$Be have been studied through a ${}^{11}$Be${(d,p)}^{12}$Be transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of ${}^{11}$Be was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in ${}^{12}$Be. The gamma-ray detection enabled a clear identification of the four known bound states in ${}^{12}$Be, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from distorted wave Born approximation (DWBA) calculations and have been compared to previous experimental and theoretical results.

Two new rotational bands of distinct character have been identified in ${}^{164}\mathrm{Hf}$. They are suggested to correspond to the long-anticipated triaxial strongly deformed (TSD) bands predicted by theoretical studies. The bands have been linked to known states, and the level spins and energies could be determined. The bands are also substantially stronger in intensity and are located at lower spins than the previously observed TSD bands in ${}^{168}\mathrm{Hf}$, hereby making ${}^{164}\mathrm{Hf}$ the best even-even system so far for the study of TSD structures in the $A\sim 160$ mass region. Cranking calculations based on the modified-oscillator model suggest that the bands are associated with four-quasiparticle configurations that involve high-$j$ intruder ${\left(i_{13/2}\right)}^2$ proton orbitals.