We calculate in chiral perturbation theory the parity-violating two-pion exchange nucleon-nucleon potentials at leading one-loop order. At a distance of $r=m_{\pi }^{-1}\simeq 1.4$ fm they amount to about $\pm 16\%$ of the parity-violating $1\pi$ exchange potential. We evaluate also the parity-violating effects arising from $2\pi$ exchange with excitation of virtual $\Delta (1232)$ isobars. These come out to be relatively small in comparison with those from diagrams with only nucleon intermediate states. The reason for this behavior, which is opposite that of the parity-conserving case, is the blocking of the dominant isoscalar central channel by CP invariance. Furthermore, we calculate the $T$ matrix related to the iteration of the parity-violating $1\pi$ exchange with the parity-conserving one. The analytical results presented in this work can be easily implemented into calculations of parity-violating nuclear observables.

We show that the differential cross section $d\sigma /\mathit{dt}$ of the $\gamma p\to \varphi p$ reaction at threshold is finite and its value is crucial to the mechanism of ϕ-meson photoproduction and for the models of $\varphi N$ interaction.

A dispersive-optical-model analysis of $p+$${}^{40,42,44,48}\mathrm{Ca}$ and $n+$${}^{40}\mathrm{Ca}$ interactions has been carried out. The real and imaginary potentials have been constrained by fitting elastic-scattering data, total and reaction cross sections, and level properties of valence hole states deduced from $(e,e^{\text{'}}p)$ data. The resulting surface imaginary potential increases with asymmetry for protons, implying that in heavier Ca isotopes, protons experience stronger long-range correlations. Presently, there is not enough data for neutrons to determine their asymmetry dependence. Global optical-model fits usually assume that the neutron asymmetry dependence is equal in magnitude, but opposite in sign, to that for protons. Such a dependence was found to give unphysical results for heavy Ca isotopes. The dispersive optical model is shown to be a useful tool for data-driven extrapolations to the drip lines. Neutron and proton data at larger asymmetries are needed to achieve more reliable extrapolations. The present analysis predicts ${}^{60}\mathrm{Ca}$ and ${}^{70}\mathrm{Ca}$ to be bound, while the intermediate isotopes are not.

High-spin states of ${}^{191,193}\mathrm{Au}$ and ${}^{192}\mathrm{Pt}$ have been populated in the ${}^{186}\mathrm{W}$(${}^{11}\mathrm{B}$, xn) and ${}^{186}\mathrm{W}$(${}^{11}\mathrm{B}$, p4n) reactions, respectively, at a beam energy of 68 MeV and their γ decay was studied using the YRAST Ball detector array at the Wright Nuclear Structure Laboratory at Yale University. The level scheme of ${}^{193}\mathrm{Au}$ has been extended up to $I^{\pi }=55/2^{+}$. New transitions were observed also in ${}^{191}\mathrm{Au}$ and ${}^{192}\mathrm{Pt}$. Particle-plus-Triaxial-Rotor (PTR) and Total Routhian Surface (TRS) calculations were performed to determine the equilibrium deformations of the Au isotopes. The predictions for oblate deformations in these nuclei are in agreement with the experimental data. Development of nonaxial shapes is discussed within the framework of the PTR model.

Lifetimes of exited states in ${}^{134}\mathrm{Pr}$ were measured by means of the recoil distance Doppler-shift and Doppler-shift attenuation techniques. The branching ratios and the electric or magnetic character of the transitions were also investigated. The experiments were performed at IReS, Strasbourg, using the EUROBALL IV spectrometer, in conjunction with the inner bismuth germanate ball and the Cologne coincidence plunger apparatus. Exited states in ${}^{134}\mathrm{Pr}$ were populated in the fusion-evaporation reaction ${}^{119}\mathrm{Sn}$(${}^{19}\mathrm{F}$, 4$n$)${}^{134}\mathrm{Pr}$. The possible chiral interpretation of twin bands was investigated in the two-quasiparticle triaxial rotor and interacting boson-fermion-fermion models. The analysis of the wave functions has shown that the possibility for the angular momenta of the proton, neutron, and core to find themselves in the favorable, almost orthogonal geometry, is present but is far from being dominant. The structure is characterized by large β and γ fluctuations. The existence of doublets of bands in ${}^{134}\mathrm{Pr}$ can be attributed to weak chirality dominated by shape fluctuations.

Exact calculations are performed for proton emission from triaxial nuclei by extending the nonadiabatic quasiparticle method to include the triaxial degree of freedom. We present for the first time a proper formalism for triaxial proton emitters, which includes the treatment of the pairing residual interaction and the coupling with the excited states of the daughter nucleus. The results for the nuclei ${}^{161}\mathrm{Re}$ and ${}^{185}\mathrm{Bi}$ are discussed. In contrast to an earlier prediction, where this problem was addressed with approximate methods, a weak dependance on triaxial deformation, especially in the nonadiabatic case, is found.

Excited states in the highly neutron deficient odd-odd nucleus ${}^{170}\mathrm{Ir}$ have been investigated. The experiment was performed using the ${}^{112}\mathrm{Sn}$(${}^{60}\mathrm{Ni}$, $\mathit{pn}$)${}^{170}\mathrm{Ir}$ reaction and employing the recoil-decay tagging technique. Gamma rays were detected using the JUROGAM γ-ray spectrometer and those belonging to ${}^{170}\mathrm{Ir}$ were selected based on recoil identification provided by the RITU gas-filled recoil separator and the GREAT spectrometer at the RITU focal plane. A partial level scheme of ${}^{170}\mathrm{Ir}$ is presented for the first time. New α-decay branches are assigned to ${}^{170}\mathrm{Ir}$ and a tentative level structure for ${}^{166}\mathrm{Re}$ is deduced from a study of the α-decay fine structure and the associated α-γ correlations.

The reaction mechanism of projectile fragmentation at intermediate energies has been investigated by observing the target dependence of the production cross sections of very neutron rich nuclei. Measurement of longitudinal momentum distributions of projectile-like fragments in a broad range of fragment mass and charge was performed using a 100 MeV/nucleon ${}^{40}\mathrm{Ar}$ beam incident on Be and Ta targets. By measurement of the fragment momentum distribution, a parabolic mass dependence of the momentum peak shift was observed in the results of both targets, and light-fragment acceleration was found only in the Be-target data. The analysis of production cross sections revealed an obvious enhancement of the target dependence except for a target size effect when the neutron excess is increased. This result implies the breakdown of factorization of production cross sections for very neutron rich nuclei near the drip line.

Within the concept of the dinuclear system (DNS), a dynamical model is proposed for describing the formation of superheavy nuclei in complete fusion reactions by incorporating the coupling of the relative motion to the nucleon transfer process. The capture of two heavy colliding nuclei, the formation of the compound nucleus, and the de-excitation process are calculated by using an empirical coupled channel model, solving a master equation numerically and applying statistical theory, respectively. Evaporation residue excitation functions in cold fusion reactions are investigated systematically and compared with available experimental data. Maximal production cross sections of superheavy nuclei in cold fusion reactions with stable neutron-rich projectiles are obtained. Isotopic trends in the production of the superheavy elements $Z=110,$ 112, 114, 116, 118, and 120 are analyzed systematically. Optimal combinations and the corresponding excitation energies are proposed.

We have studied the structure of $K^{-}\mathit{pp}$ nuclear cluster comprehensively by solving this three-body system exactly in a variational method starting from the Ansatz that the $\Lambda (1405)$ resonance $(\equiv {\Lambda }^{*})$ is a $K^{-}p$ bound state. We have found that our original prediction for the presence of $K^{-}\mathit{pp}$ as a compact bound system with $M=2322$ MeV/$c^2,B_K=48$ MeV, and $\Gamma =60$ MeV remains unchanged by varying the $\overline{K}N$ and $\mathit{NN}$ interactions widely as far as they reproduce $\Lambda (1405)$. The structure of $K^{-}\mathit{pp}$ reveals a molecular feature, namely the $K^{-}$ in ${\Lambda }^{*}$ as an “atomic center” plays a key role in producing strong covalent bonding with the other proton. We have shown that the elementary process, $p+p\to K^{+}+{\Lambda }^{*}+p$, which occurs in a short impact parameter and with a large momentum transfer ($Q~1.6$ GeV/$c$), leads to unusually large self-trapping of ${\Lambda }^{*}$ by the participating proton, because the ${\Lambda }^{*}\text{−}p$ system exists as a compact doorway state propagating to $K^{-}\mathit{pp}$ ($R_{{\Lambda }^{*}p}~1.67$ fm).

The helicity dependence of the $\overrightarrow{\gamma }\overrightarrow{d}\to {\pi }^{-}\mathit{pp},\overrightarrow{\gamma }\overrightarrow{d}\to {\pi }^{+}\mathit{nn}$, and $\overrightarrow{\gamma }\overrightarrow{d}\to {\pi }^0\mathit{np}$ reaction channels is studied for incident photon energies from threshold up to the Δ(1232) resonance with inclusion of leading $\pi \mathit{NN}$ effects. The doubly polarized total and differential cross sections for parallel and antiparallel helicity states are predicted. Then the contribution of various channels to the deuteron spin asymmetry and the double polarization $E$ asymmetry is calculated. In addition, the contribution to the Gerasimov-Drell-Hearn (GDH) integral from separate channels is evaluated by explicit integration up to a photon lab energy of 350 MeV. Sizeable effects from final-state interactions, specially for ${\pi }^0$ production, are found. The sensitivity of the results to the elementary pion photoproduction operator is also investigated. Considerable dependence of the results on the elementary amplitude is found. We expect that these results may be useful to interpret the recent measurements from LEGS@BNL, A2, and GDH@MAMI Collaborations.

The heavy-ion radiative capture reaction, ${}^{12}\mathrm{C}$(${}^{12}\mathrm{C}$,γ), has been investigated at energies both on- and off-resonance, with a particular focus on known resonances at $E_{\mathrm{c}.\mathrm{m}.}=6.0$, 6.8, 7.5, and 8.0 MeV. Gamma rays detected in a BGO scintillator array were recorded in coincidence with ${}^{24}\mathrm{Mg}$ residues at the focal plane of the DRAGON recoil separator at TRIUMF. In this manner, the relative strength of all decay pathways through excited states up to the particle threshold could be examined for the first time. Isovector $M1$ transitions are found to be a important component of the radiative capture from the $E_{\mathrm{c}.\mathrm{m}.}=6.0$ and 6.8 MeV resonances. Comparison with Monte Carlo simulations suggests that these resonances may have either $J=0$ or 2, with a preference for $J=2$. The higher energy resonances at $E_{\mathrm{c}.\mathrm{m}.}=7.5$ and 8.0 MeV have a rather different decay pattern. The former is a clear candidate for a $J=4$ resonance, whereas the latter has a dominant $J=4$ character superposed on a $J=2$ resonant component underneath. The relationship between these resonances and the well-known quasimolecular resonances as well as resonances in breakup and electrofission of ${}^{24}\mathrm{Mg}$ into two ${}^{12}\mathrm{C}$ nuclei are discussed.

The mean free paths and in-medium scattering cross sections of energetic nucleons in neutron-rich nucleonic matter are investigated using the nucleon optical potential obtained within the relativistic impulse approximation with the empirical nucleon-nucleon scattering amplitudes and the nuclear densities obtained in the relativistic mean-field model. It is found that the isospin-splitting of nucleon mean free paths, sensitive to the imaginary part of the symmetry potential, changes its sign at certain high kinetic energy. The in-medium nucleon-nucleon cross sections are analytically and numerically demonstrated to be essentially independent of the isospin asymmetry of the medium and increase linearly with density in the high-energy region where the relativistic impulse approximation is applicable.

The accuracy of the variation before (VBP) and after (VAP) particle-number projection methods, the Lipkin-Nogami (LN) prescription, and the projected Lipkin-Nogami (PLN) method have been studied using two exactly solvable models. It is shown that the VBP and the LN methods are rather dubious not only in a weak pairing regime, but also in strong pairing for the evaluation of quantities other than the ground state energy. The PLN method provides good results for the ground and the excited state energies, but it must be used with caution for the occupation probabilities and the observables that strongly depend on it. It seems that the VAP is the only suitable method for a global description of the nuclear properties.

We argue that “ridge” in two-particle correlation function associated with hard trigger at BNL Relativistic Heavy Ion Collider (RHIC) heavy ion collisions is naturally explained by an interrelation of jet quenching and hydrodynamical transverse flow. The excess particles forming the ridge are produced by QCD bremsstrahlung along the beam (and thus have wide rapidity distribution) and then boosted by transverse flow. Nontrivial correlation between directions of the jet and the radial flow is provided by jet quenching: our straightforward and basically parameter-independent calculation reproduces the angular shape, width, and other properties of the ridge.

The formation and suppression dynamics of $J/\Psi ,{\chi }_c$, and ${\Psi }^{\text{'}}$ mesons is studied within the hadron-string-dynamics (HSD) transport approach for Au+Au reactions at the top energy currently available at the BNL Relativistic Heavy Ion Collider (RHIC) of $\sqrt{s}=200$ GeV. Two prominent models, which have been discussed for more than a decade, are incorporated, i.e., the hadronic comover absorption and reformation model as well as the quark-gluon plasma (QGP) threshold scenario, and compared with available experimental data. Our studies demonstrate that both scenarios, which are compatible with experimental observation at SPS energies, fail severely at RHIC energies. This combined analysis, together with the underestimation of charm elliptic flow, proves that the dynamics of $c,\overline{c}$ quarks are dominated by partonic interactions in the strong QGP and can be neither modeled by hadronic interactions nor described appropriately by color screening alone.

Temperature-dependent isovector neutron-proton $(\mathit{np})$ pairing gap equations have been established by means of the path integral approach. These equations generalize the BCS ones for the pairing between like particles at finite temperature. The method has been numerically tested using the one-level model. It has been shown that the gap parameter ${\Delta }_{\mathit{np}}$ has a behavior analogous to that of ${\Delta }_{\mathit{nn}}$ and ${\Delta }_{\mathit{pp}}$ as a function of the temperature: one notes the presence of a critical temperature. Moreover, it has been shown that the isovector pairing effects remain beyond the critical temperature that corresponds to the pairing between like particles.

It is shown that hyperspherical harmonics can be represented in a form typical of traditional microscopic cluster models. This allows those hyperharmonics that are responsible for long-range behavior of valence nucleons in loosely bound nuclei to be selected. The hyperspherical cluster model based on such hyperharmonics is tested for ${}^5\mathrm{He}$ in a “toy model” that uses a simplified description of the ${}^4\mathrm{He}$ core. The comparison of the hyperspherical expansion to a microscopic cluster model calculation confirms the feasibility of the hyperspherical treatment of long-range behavior by basis convergence only.

Recent lattice calculations showed that heavy quarkonia will survive beyond the phase-transition temperature and will dissolve at different temperatures depending on the type of the quarkonium. In this work, we calculate the thermal width of a quarkonium at finite temperature before it dissolves into open heavy quarks. The input of the calculation are the parton quarkonium dissociation cross section to next-to-leading order in quantum chromodynamics (QCD), the quarkonium wave function in a temperature-dependent potential from lattice QCD, and a thermal distribution of partons with thermal masses. We find that for the $J/\psi$, the total thermal width above $1.4T_c$ becomes larger than 100 to 250 MeV, depending on the effective thermal masses of the quark and gluon, which we take between 400 and 600 MeV. Such a width corresponds to an effective dissociation cross section by gluons between 1.5 and 3.5 mb and by quarks 1 to 2 mb at $1.4T_c$. However, at similar temperatures, we find a much smaller thermal width and effective cross section for the $\Upsilon$.