I examine the role of final state interactions in cold nuclear matter in modifying hadron production on nuclear targets with leptonic or hadronic beams. I demonstrate the extent to which available experimental data in electron-nucleus collisions can give direct information on final state effects in hadron-nucleus and nucleus-nucleus collisions. For hadron-nucleus collisions, a theoretical estimate based on a parton energy loss model tested in lepton-nucleus collisions shows a large effect on midrapidity hadrons at fixed target experiments. At energies currently available at the BNL Relativistic Heavy Ion Collider, the effect is large for negative rapidity hadrons but mild at midrapidity. This final state cold hadron quenching needs to be taken into account in jet tomographic analysis of the medium created in nucleus-nucleus collisions.

${}^{30}\mathrm{P}$ has been studied by in-beam γ-spectroscopy following the fusion-evaporation reaction ${}^{16}\mathrm{O}$(${}^{16}\mathrm{O}$,$\mathit{pn}$) at $E_{\mathrm{lab}}=40$ MeV, using the Indian National Gamma (Clover) Array (INGA) up to moderate spins ($I=5$). Polarization measurements of seven gamma rays have been performed for the first time. To understand the underlying structure of the levels and transition mechanisms, experimental data have been compared with the results from large basis cross-shell shell model calculations. The results for the negative parity states are especially important in this respect. Positive parity states indicate an onset of collectivity, whereas the negative parity states are members of ν-π multiplets.

Near-barrier fusion excitation functions for the ${}^{14}\mathrm{C}$ and ${}^{18}\mathrm{O}+{}^{208}\mathrm{Pb}$ reactions have been analyzed in the framework of the barrier-passing model using different forms of the nuclear potential and the phenomenology of a fluctuating barrier. The best-fit fusion potentials were used to estimate cluster decay probabilities from the corresponding ground states of Ra and Th (i.e., for the inverse decay process). The analysis supports the “α-decay-like” scenario for carbon and oxygen emission from these nuclei.

The elastic scattering of light halo nuclei in the field of heavy targets has been studied for collision energies below the Coulomb barrier. Based on the assumption that the neutron halo follows the projectile adiabatically along its classical trajectory, a dynamic polarization potential is derived which describes both the (electrical) polarization as well as the breakup of the projectile in the field of the target. Detailed computations have been carried out for the elastic scattering of ${}^6\mathrm{He}+{}^{209}\mathrm{Bi}$ at energies between 14.7 MeV and 19.1 MeV near to the Coulomb barrier. It is demonstrated that the polarization of the halo nucleus leads to a clear decrease of the (elastic) scattering cross section in excellent agreement with a recent measurement by Aguilera et al. [Phys. Rev. Lett. 84, 5058 (2000)].

Excited states in ${}^{149}\mathrm{La}$, populated in the spontaneous fission of ${}^{248}\mathrm{Cm}$, were studied with the EUROGAM2 array. A new $\Delta I=2$ band found in ${}^{149}\mathrm{La}$ is interpreted as the $\alpha =-1/2$ branch of the $\pi 3/2^{-}$[402] configuration. The bandhead has spin $7/2^{-}$ because the $3/2^{-}$ and $5/2^{-}$ levels are pushed up by the Coriolis interaction. The $7/2^{-}$ level is located not higher than 30 keV above the ground state and may form a long-lived isomer if spin and parity of the g.s. is $3/2^{+}$.

The formation of superheavy nuclei via hot fusion reactions ${}^{48}\mathrm{Ca}$$+{}^A$Ra and ${}^{48}\mathrm{Ca}$$+{}^A$Th is systematically studied within the diffusion model. The effect of the isotopic composition of actinide target on the production cross section is analyzed in detail. The results show that, as a general trend, the evaporation residue cross section exponentially depends on the difference of the effective fission barrier hight and neutron separation energy in units of the temperature. By means of this exponential relationship, the possible optimal isotopic composition of the colliding nuclei can be easily figured out before the experiment.

We construct a family of equations of state within a quasiparticle model by relating pressure, energy density, baryon density, and susceptibilities adjusted to first-principles lattice QCD calculations. The relation between pressure and energy density from lattice QCD is surprisingly insensitive to details of the simulations. Effects from different lattice actions, quark masses, and lattice spacings used in the simulations show up mostly in the quark-hadron phase transition region, which we bridge over by a set of interpolations to a hadron resonance gas equation of state. Within our optimized quasiparticle model we then examine the equation of state along isentropic expansion trajectories at small net baryon densities, as relevant for experiments and hydrodynamic simulations at RHIC and LHC energies. We illustrate its impact on azimuthal flow anisotropies and on the transverse momentum spectra of various hadron species.

The lowest order constrained variational method is applied to calculate the polarized symmetrical nuclear matter properties with the modern AV${}_{18}$ potential performing microscopic calculations. Results based on the consideration of magnetic properties show no sign of phase transition to a ferromagnetic phase.

A new effective interaction PKA1 with ρ-tensor couplings for the density dependent relativistic Hartree-Fock (DDRHF) theory is presented. It is obtained by fitting selected empirical ground state and shell structure properties. It provides satisfactory descriptions of nuclear matter and the ground state properties of finite nuclei at the same quantitative level as recent DDRHF and relativistic mean field (RMF) models. Significant improvement in the single-particle spectra is also found due to the inclusion of ρ-tensor couplings. As a result, PKA1 cures a common disease of the existing DDRHF and RMF Lagrangians, namely, the artificial shells at 58 and 92, and recovers the realistic subshell closure at 64. Moreover, the proper spin-orbit splittings and well-conserved pseudospin symmetry are obtained with the new effective interaction PKA1. Due to the extra binding introduced by the ρ-tensor correlations, the balance between the nuclear attractions and the repulsions is changed, and this constitutes the physical reason for the improvement of the nuclear shell structure.

The short-lived nuclide ${}^{44}\mathrm{Ti}$ is an important nuclide for the understanding of explosive nucleosynthesis. The main production reaction, ${}^{40}\mathrm{Ca}$($\alpha ,\gamma$)${}^{44}\mathrm{Ti}$, has been studied in inverse kinematics with the recoil mass spectrometer DRAGON located at the TRIUMF-ISAC facility in Vancouver, Canada. The temperature range relevant for α-rich freeze-out during a core-collapse supernova has been covered entirely with a ${}^{40}\mathrm{Ca}$ beam of 0.60 to 1.15 MeV/nucleon. All relevant quantities for the calculation of the astrophysical reaction rate have been measured directly. Because of many previously undiscovered resonances, the reaction rate derived from the energy dependent ${}^{44}\mathrm{Ti}$ yield is higher than the one based on previous prompt γ-ray studies commonly used in supernova models. The presented new rate results in an increased ${}^{44}\mathrm{Ti}$ production in supernovae.

We investigate the consequences of a new phenomenological model prediction of strongly reduced low-energy astrophysical $S$-factors for carbon and oxygen fusion reactions on stellar burning and nucleosynthesis. The new model drastically reduces the reaction rates in stellar matter at temperatures $T\lesssim (3\text{−}10)\times {10}^8$ K, especially at densities $\rho \gtrsim {10}^9$ g cm${}^{-3}$, in a strongly screened or even pycnonuclear burning regime. We show that these modifications change the abundance of many isotopes in massive late-type stars and in particular strongly enhance the abundances of long-lived radioactive isotopes such as ${}^{26}\mathrm{Al}$ and ${}^{60}\mathrm{Fe}$. The reduced reaction rates also significantly complicate carbon ignition (shift carbon ignition to higher temperatures and densities) in massive accreting white dwarfs exploding as type Ia supernovae and in accreting neutron stars producing superbursts. This would require much higher ignition densities for white dwarf supernovae and would widen the gulf between theoretical and inferred ignition depths for superbursts.

Nucleon-nucleon scattering in spin-triplet channels is analyzed within an effective field theory where one-pion exchange is treated nonperturbatively. Justifying this requires the identification of an additional low-energy scale in the strength of that potential. Short-range interactions are organized according to the resulting power counting, in which the leading term is promoted to significantly lower order than in the usual perturbative counting. In each channel there is a critical momentum above which the waves probe the singular core of the tensor potential and the new counting is necessary. When the effects of one- and two-pion exchange have been removed using a distorted-wave Born approximation, the residual scattering in waves with $L⩽2$ is well described by the first three terms in the new counting. In contrast, the scattering in waves with $L⩾3$ is consistent with the perturbative counting, at least for energies up to 300 MeV. This pattern is in agreement with estimates of the critical momenta in these channels.

High-spin states in ${}^{126}\mathrm{Xe}$ have been populated in the ${}^{82}\mathrm{Se}$(${}^{48}\mathrm{Ca}$,4$n$)${}^{126}\mathrm{Xe}$ reaction in two experiments, one at the VIVITRON accelerator in Strasbourg using the Euroball detector array, and a subsequent one with ATLAS at Argonne using the Gammasphere Ge-detector array. Levels and assignments made previously for ${}^{126}\mathrm{Xe}$ up to $I=20$ have been confirmed and extended. Four regular bands extending to a spin of almost $I=60$, which are interpreted as two pairs of signature partners with opposite parity, are identified for the first time. The α = 0 partner of each pair is connected to the lower-lying levels, whereas the two α = 1 partners remain floating. A fractional Doppler shift analysis of transitions in the strongest populated $(\pi ,\alpha )=(-,0)$ band provides a value of ${5.2}_{0.5}^{0.4}$ b for the transition quadrupole moment, which can be related to a minimum in the potential-energy surface calculated by the ULTIMATE CRANKER cranked shell-model code at $\epsilon \approx 0.35$ and $\gamma \approx 5^{°}$. The four lowest bands calculated for this minimum compare well with the two signature pairs experimentally observed over a wide spin range. A sharp upbend at $\hslash \omega ~1170$ keV is interpreted as a crossing with a band involving the $j_{15/2}$ neutron orbital, for which pairing correlations are expected to be totally quenched. The four long bands extend to within ∼5 spin units of a crossing with an yrast line defined by calculated hyperdeformed transitions and will serve as important stepping stones into the spin region beyond 60ħ for future experiments.

The properties of Λ hypernuclei in a broad mass region are studied by using a deformed Hartree-Fock approach using realistic nucleonic Skyrme forces, pairing correlations, and a microscopically determined lambda-nucleon interaction based on Brueckner-Hartree-Fock calculations of hypernuclear matter. The results suggest that the core nuclei and the corresponding hypernuclei have similar deformations with the same sign. Some light single-Λ hypernuclei are substantially deformed and the Λ binding energy is modified by the deformation.

We investigate the role of two-quasiparticle isomeric states along the proton drip line, using configuration-constrained potential-energy-surface calculations. In contrast to even-even nuclei, odd-odd nuclei can have coexisting low-lying two-quasiparticle states. The low excitation energy and high angular momentum can lead to long-lived isomers. Also, because of the hindrance by spin selection, the probabilities of β and proton decays from high-spin isomers can be reduced significantly. The present calculations reproduce reasonably well the available data for observed isomers in such nuclei. Unobserved high-spin isomers are predicted, which could be useful for future experimental studies of exotic nuclei at and beyond the proton drip line.

We estimate the ratios of bare astrophysical $S$-factors at zero incident energy for proton- and deuteron-induced reactions in a model that assumes a compound nucleus formation probability plus a statistical decay. The obtained ratios agree well with available experimental values, as far as the reactions which have dominant $s$-wave entrance channel components are investigated. Due to its simplicity the model could be used as a guidance for predictions on reactions that have not been investigated yet.

The properties of nuclei embedded in an electron gas are studied within the relativistic mean-field approach. These studies are relevant for nuclear properties in astrophysical environments such as neutron-star crusts and supernova explosions. The electron gas is treated as a constant background in the Wigner-Seitz cell approximation. We investigate the stability of nuclei with respect to α and β decay. Furthermore, the influence of the electronic background on spontaneous fission of heavy and superheavy nuclei is analyzed. We find that the presence of the electrons leads to stabilizing effects for both α decay and spontaneous fission at high electron densities. Furthermore, the screening effect shifts the proton dripline to more proton-rich nuclei, and the stability line with respect to β-decay is shifted to more neutron-rich nuclei. Implications for the creation and survival of very heavy nuclear systems are discussed.

To describe Λ(1405) as a resonance in baryon-meson scattering, we have investigated the $q^3$-$q\overline{q}$ scattering system with the flavor-singlet $q^3(0s){}^2(0p)$ state (the ${\Lambda }^1$ pole). The scattering is treated by the quark cluster model (QCM). The ${\Lambda }^1$ pole is treated as a bound state embedded in the continuum. We have found that a peak appears below the $\mathrm{N}\overline{\mathrm{K}}$ threshold in the spin-$\frac{1}{2}$, isospin-0 channel even if the mass of the ${\Lambda }^1$ pole is above the threshold. This peak disappears when the coupling to the ${\Lambda }^1$ pole is switched off. Using the observed hadron mass in the kinetic part of QCM is also found to be important in reproducing a peak just below the $\mathrm{N}\overline{\mathrm{K}}$ threshold.

Asymmetric nuclear matter is investigated in the low-density region below the nuclear saturation density. Microscopic calculations based on the Dirac-Brueckner-Hartree-Fock (DBHF) approach with realistic nucleon-nucleon potentials are used to adjust a low-density functional. This functional is constructed on a density expansion of the relativistic mean-field theory that allows a clear interpretation of the role of the mesons in the equation of state. It is shown that a correction term should be added to the functional to take into account the effects beyond the mean field. Two functionals with different corrections are obtained and their topological properties have been studied. Those functionals converge to predict a reduction of the spinodal zone in asymmetric nuclear matter by about 15–20% and an isoscalar unstable mode closer to the constant $Z/A$ direction than the functional without correction.