Experimental level densities for ${}^{171,172}\mathrm{Yb},$ ${}^{166,167}\mathrm{Er},$ ${}^{161,162}\mathrm{Dy},$ and ${}^{148,149}\mathrm{Sm}$ are analyzed within the microcanonical ensemble. In the even isotopes at excitation energies $E<\mathrm{}2\mathrm{}\mathrm{MeV},$ the Helmholtz free energy F signals the transition from zero to two quasiparticles. For $E>\mathrm{}2\mathrm{}\mathrm{MeV},$ the odd and even isotopes reveal a surprisingly constant F at a critical temperature $T_c\sim 0.5\mathrm{MeV},$ indicating the continuous melting of nucleon Cooper pairs as function of excitation energy.

We develop an improved statistical multifragmentation model that provides the capability to calculate calorimetric and isotopic observables with precision. With this new model we examine the influence of nuclear isospin on the fragment elemental and isotopic distributions. We show that the proposed improvements on the model are essential for studying isospin effects in nuclear multifragmentation. In particular, these calculations show that accurate comparisons to experimental data require that the nuclear masses, free energies, and secondary decay must be handled with higher precision than many current models accord.

We demonstrate the ability of complete sets of exclusive $(\overrightarrow{p},2\mathrm{}\overrightarrow{p})$ polarization transfer observables to discriminate between different model ingredients of the relativistic distorted wave impulse approximation (DWIA). Spin observables are identified, which are sensitive to Dirac versus Schrödinger dynamical equations of motion, different distorting optical potentials, finite-range versus zero-range approximations to the DWIA, as well as medium-modified meson-nucleon coupling constants and meson masses. In particular, we consider the knockout of protons from the ${3s}_{1/2},$ ${2d}_{3/2},$ and ${2d}_{5/2}$ states in ${}^{208}\mathrm{Pb},$ at an incident laboratory kinetic energy of 202 MeV, and for coincident coplanar scattering angles (28.0°, -54.6°). The reaction kinematics are chosen so as to maximize the influence of distortion effects, while still maintaining the validity of the impulse approximation, and also avoiding complications associated with the inclusion of recoil corrections in the relativistic Dirac equation.

Spatial fluctuations as well as event-to-event fluctuations of charged particles produced in central ${}^{32}\mathrm{S}-\mathrm{A}\mathrm{g}/\mathrm{B}\mathrm{r}$ interactions at $200A\mathrm{G}\mathrm{e}\mathrm{V}/c$ are investigated by using a new technique called erraticity analysis. A general scaling law between the erraticity moments and number of phase-space intervals is observed, and the values of erraticity parameters are obtained. These parameters can serve a very useful purpose for model calculations of the multiparticle production mechanism in high-energy heavy-ion collisions that takes into account possible sources of fluctuations.

Coulomb corrections to perturbation theory for producing electron-positron pairs in ultrarelativistic heavy ion collisions are considered in a part-analytical, part-numerical approach. Production probabilities are reduced from perturbation theory with increasing charge of the colliding heavy ions, as has been previously argued in the literature. It is shown here that the reduction from perturbation theory comes from the appropriate physical spatial cutoff of the electromagnetic potentials arising from the colliding ultrarelativistic heavy ions.

Measurements of the angular distributions of target and double-spin asymmetries for the ${\Delta }^{+}\mathrm{}\left(1232\right)\mathrm{}$ in the exclusive channel $\overrightarrow{p}\left(\overrightarrow{e}{,e}^{\prime }p\right){\pi }^0$ obtained at the Jefferson Lab in the $Q^2$ range from 0.5 to $1.5{\mathrm{GeV}}^2{/c}^2$ are presented. Results of the asymmetries are compared with the unitary isobar model [D. Drechsel et al., Nucl. Phys. A645, 145 (1999)], dynamical models [T. Sato and T. S. Lee, Phys. Rev. C 54, 2660 (1996); S. S. Kamalov et al., Phys. Lett. B 27, 522 (2001)], and the effective Lagrangian theory [R. M. Davidson et al., Phys. Rev. D 43, 71 (1991)]. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly.

We demonstrate that one can use the occurrence of charge symmetry breaking as a tool to explore the $\eta$-nucleus interaction near the $\eta$ threshold. Based on indications that the cross section ratio of ${\pi }^{+}$ and ${\pi }^0$ production on nuclei deviates from the isotopic value in the vicinity of the $\eta$ production threshold, due to, e.g., ${\pi }^0-\eta$ mixing, we argue that a systematic study of this ratio as a function of the energy would allow to pin down the sign of the real part of the $\eta$-nucleus scattering length. This sign plays an important role in the context of the possible existence of $\eta$-nucleus bound states.

With the global color symmetry model being extended to finite chemical potential, we study the density dependence of the local and nonlocal scalar quark condensates in nuclear matter. The calculated results indicate that the quark condensates increase smoothly with the increasing of nuclear matter density before the critical value (about $12{\rho }_0)$ is reached. It also manifests that the chiral symmetry is restored suddenly as the density of nuclear matter reaches its critical value. Meanwhile, the nonlocal quark condensate in nuclear matter changes nonmonotonously against the space-time distance among the quarks.

Using the quark-gluon plasma motivated threshold model, where all the $J/\psi \mathrm{’}\mathrm{s}$ are suppressed above a threshold density, we have analyzed the latest version of the NA50 data on the centrality dependence of $J/\psi$ over the Drell-Yan ratio in $158\mathrm{GeV}/c$ $\mathrm{Pb}+\mathrm{Pb}$ collisions. The data are not well explained in the model, unless the threshold density is smeared to a large extent. Large smearing of the threshold density effectively excludes creation of any deconfined medium in the collision.

Three $\gamma$-decaying isomers in the $N=Z+1\mathrm{}$ nucleus ${}^{95}\mathrm{Ag}$ have been identified for the first time. The ${}^{95}\mathrm{Ag}$ nuclei were produced via the ${}^{58}\mathrm{Ni}{(}^{40}\mathrm{Ca},p2n)$ reaction and separated by using the GSI on-line mass separator. The emitted $\gamma$ rays were measured with a multi-Ge detector setup in anticoincidence with positrons. Three individual $\gamma$-decay cascades have been identified and assigned to ${}^{95}\mathrm{Ag},$ representing the depopulation of isomers at 344-, 2531-, and 4859-keV excitation energy with tentative spin-parity assignments of ${(1/2\mathrm{}}^{-}),{(23/2\mathrm{}}^{+}),$ and ${(37/2\mathrm{}}^{+}),$ respectively. The spin and parity assignments are based on a comparison with shell-model predictions employing empirical interactions.

We present calculated values of energies and widths for astrophysically interesting states at 7–8 MeV excitation energy, based—whenever possible—on information from mirror levels in ${}^{18}\mathrm{O}.$

The structure of odd-mass isotopes of Cs and Xe is described in the framework of the proton-neutron interacting boson-fermion model. The model provides a consistent description of $\beta$ decay from Cs to Xe nuclei of mass number $A=125,$ 127, and 129.

We have calculated the expected width for ${}^{12}\mathrm{O}$ sequential decay through a broad ${}^{11}\mathrm{N}\mathrm{}(\mathrm{g}.\mathrm{s}.\mathrm{})\mathrm{}$ to ${}^{10}\mathrm{C}\mathrm{}(\mathrm{g}.\mathrm{s}.\mathrm{})\mathrm{}$ and for simultaneous ${(}^2\mathrm{He})$ decay by convoluting $2p$ decay widths with the $\mathrm{pp}$ relative energy. Both widths are found to be about 60 keV.

Coherent and incoherent dipolar $\gamma$-ray emission is studied in a fully dynamical approach by means of the constrained molecular dynamics model. The study is focused on the system ${}^{40}\mathrm{Ca}{+}^{48}\mathrm{Ca}$ for which recently experimental data have been collected at 25 MeV/nucleon. The approach allows us to explain the experimental results in a self-consistent way without using statistical or hybrid models. Moreover, calculations performed at higher energy show interesting correlations between the fragment formation process, the degree of collectivity, and the coherence degree of the $\gamma$-ray emission process.

The ground state and first excited state of ${}^{15}\mathrm{F}$ were measured by the method of elastic resonance scattering in inverse kinematics. A secondary beam of 115 MeV/nucleon ${}^{14}\mathrm{O}$ was slowed down to 8 MeV/nucleon and energy bunched before stopping in a ${\mathrm{C}}_2{\mathrm{H}}_4$ target. The ${}^{15}\mathrm{F}$ excitation energy spectrum was extracted from elastically scattered protons at $0°.$ The ${1/2}^{+}$ ground state resonance of ${}^{15}\mathrm{F}$ was determined to be unbound with respect to single-proton emission by $1.51\pm 0.11\mathrm{MeV},$ corresponding to a mass excess of $16.81\pm 0.11\mathrm{MeV}.$ The ${5/2}^{+}$ first excited state resonance is unbound by $2.853\pm 0.045\mathrm{MeV}$ leading to an excitation energy of $1.34\pm 0.15\mathrm{MeV}.$ A comparison with systematics of single-nucleon separation energies and theoretical models suggests that ${}^{11}\mathrm{N}$ should be unbound by about $1.5\pm 0.15\mathrm{MeV}.$

We explore the consequences of a freeze-out criterion for heavy-ion collisions, based on pion escape probabilities from the hot and dense but rapidly expanding collision region. The influence of the expansion and the scattering rate on the escape probability is studied. The temperature dependence of this scattering rate favors a low freeze-out temperature of $\sim 100\mathrm{MeV}.$ In general, our results support freeze-out along finite four-volumes rather than sharp three-dimensional hypersurfaces, with high-$p_{\perp }$ particles decoupling earlier from smaller volumes. We compare our approach to the proposed universal freeze-out criteria using the pion phase-space density and its mean free path.

The ab initio no-core shell model (NCSM) is extended to include a realistic three-body interaction in calculations for p-shell nuclei. The NCSM formalism is reviewed and new features needed in calculations with three-body forces are discussed in detail. We present results of first applications to ${}^{6,7}\mathrm{Li},$ ${}^6\mathrm{He},$ ${}^{7,8,10}\mathrm{Be},$ ${}^{10,11,12}\mathrm{B},$ ${}^{12}\mathrm{N},$ and ${}^{10,11,12,13}\mathrm{C}$ using the Argonne ${\mathrm{V}8\mathrm{}}^{\prime }$ nucleon-nucleon (NN) potential and the Tucson-Melbourne ${\mathrm{TM}}^{\prime }\mathrm{}\left(99\right)\mathrm{}$ three-nucleon interaction (TNI). In addition to increasing the total binding energy, we observe a substantial sensitivity in the low-lying spectra to the presence of the realistic three-body force and an overall improvement in level ordering and level spacing in comparison to experiment. The greatest sensitivity occurs for states where the spin-orbit interaction strength is known to play a role. In particular, with the TNI we obtain the correct ground-state spin for ${}^{10,11,12}\mathrm{B}$ and ${}^{12}\mathrm{N},$ contrary to calculations with NN potentials only.

The neutron-deuteron $\mathrm{}\left(\mathrm{nd}\right)\mathrm{}$ doublet ${(}^2{a}_{\mathrm{nd}})$ and quartet ${(}^4{a}_{\mathrm{nd}})$ scattering lengths were calculated based on the nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ interactions CD Bonn 2000, AV18, Nijm I, II, and 93 alone and in selected combinations with the Tucson-Melbourne (TM), a modified version thereof, TM99, and the Urbana IX three-nucleon $\mathrm{}\left(3N\right)\mathrm{}$ forces. For each $\mathrm{NN}$ and $3N$ force combination the ${}^3\mathrm{H}$ binding energy was also calculated. In case of TM99 and Urbana IX the 3NF parameters were adjusted to the ${}^3\mathrm{H}$ binding energy. In no case (using $\mathrm{np}-\mathrm{nn}$ forces) the experimental value of ${}^2{a}_{\mathrm{nd}}$ was reached. We also studied the effect of the electromagnetic interactions in the form introduced in AV18. Switching them off for the various nuclear force models leads to shifts of up to $+0.04\mathrm{}\mathrm{fm}$ for ${}^2{a}_{\mathrm{nd}},$ which is significant for present day standards. The electromagnetic effects also have a noticeable effect on ${}^4{a}_{\mathrm{nd}},$ which is extremely stable under the exchange of the nuclear forces otherwise. Only if the electromagnetic interactions are included, the current nuclear forces describe the experimental value. As a consequence of the failure to reproduce ${}^2{a}_{\mathrm{nd}}$ also the newly measured coherent $\mathrm{nd}$ scattering length ${(b}_{\mathrm{nd}})$ cannot be reproduced. The current nuclear force models predict ${}^3\mathrm{H}$ binding energies and the ${}^2{a}_{\mathrm{nd}}$ values around an averaged straight line (Phillips line), but this correlation is broken visibly. This allows us to use ${}^2{a}_{\mathrm{nd}}$ and the ${}^3\mathrm{H}$ binding energy as independent low-energy observables.

The $\gamma$ rays following the $72s$ ${}^{150}\mathrm{Ho}$ $2^{-}$ Gamow-Teller $\beta$ decay have been investigated with the CLUSTER CUBE setup, an array of six EUROBALL CLUSTER Ge detectors in close cubic geometry, providing a $\gamma$ ray detection sensitivity of $2\times {10}^{-5}$ per $\beta$-parent decay for $\gamma$-ray energies up to 5 MeV. The fine structure of the Gamow-Teller resonance at 4.4-MeV excitation in ${}^{150}\mathrm{Dy}$ has been studied. The resolved levels are compared with Shell Model predictions.

Rearrangement effects in light hypernuclei are investigated in the framework of the Brueckner theory. We can estimate without detailed numerical calculations that the energy of the $\alpha$ core is reduced by more than 2.5 MeV when the $\Lambda$ adheres to ${}^4\mathrm{He}$ to form ${}_{\Lambda }^5\mathrm{He}.$ Similar assessment of rearrangement contributions is essential to deduce the strength of $\Lambda \Lambda$ interaction from experimentally observed $\Delta B_{\Lambda \Lambda }.$ The recently observed experimental value of $\sim 1\mathrm{MeV}$ for the $\Delta B_{\Lambda \Lambda }$ of ${}_{\Lambda \Lambda }^6\mathrm{He}$ suggests that the matrix element of $〈\Lambda \Lambda |v|\Lambda \Lambda 〉$ in ${}_{\Lambda \Lambda }^6\mathrm{He}$ is around $-2\mathrm{MeV}.$