Partition functions, multiplicity distributions, and isospin fluctuations are calculated for canonical ensembles in which additive quantum numbers as well as total isospin are strictly conserved. When properly accounting for Bose-Einstein symmetrization, the multiplicity distributions of neutral pions in a hadronic gas are significantly broader as compared to the nondegenerate case. Inclusion of resonances compensates for this broadening effect. Recursion relations are derived, which allow calculation of exact results with modest computer time.

New experimental data on ${}^{73}\mathrm{As}$ were used to test the predictions of the U(6/12) supersymmetry scheme in its vibrational limit. A reasonable description of the energies and branching ratios of the low-lying states was obtained using the U(6/12) model. A comparison with former interacting boson-fermion model results is also discussed.

We present a hydrodynamic assessment of preliminary particle spectra observed in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{}\mathrm{GeV}.$ The hadronic part of the underlying equation of state is based on explicit conservation of (measured) particle ratios throughout the resonance gas stage after chemical freezeout by employing chemical potentials for stable mesons, nucleons, and antinucleons. We find that under these conditions the data (in particular, the proton spectra) favor a low freezeout temperature of around $\sim 100\mathrm{MeV}.$ Furthermore, we show that through inclusion of a moderate prehydrodynamic transverse flow field the shape of the spectra improves with respect to the data. The effect of the initial transverse boost on elliptic flow and the freezeout geometry of the system is also discussed.

We study the production of dileptons in relativistic nucleon-nucleon collisions. Additionally, to the traditional dilepton production channels [vector meson decays, meson and $\Delta \mathrm{}\left(1232\right)\mathrm{}$ Dalitz decays], we included in our model as new dilepton sources the Dalitz decay of higher unflavored baryon resonances with $\mathrm{spin}<~5/2$ and $\mathrm{mass}<~2.25{\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{c}}^2.$ The contributions of these new channels are estimated, using experimental information about the $N\gamma$ decays of the resonances and have large uncertainties. The obtained dilepton spectra are compared to the experimental data by the DiLepton Spectrometer (DLS, Lawrence Berkeley National Laboratory). Predictions for the High Acceptance Di-Electron Spectrometer (HADES) of the Heavy Ion Synchrotron SIS at GSI, Darmstadt are also discussed. In spite of the large uncertainties of the higher resonance Dalitz decay contributions, we are able to draw the conclusion that these contributions are negligible compared to the other dilepton sources and do not influence the detectability of the $\phi$ and $\omega$ vector meson peaks.

We study pion absorption on ${}^3\mathrm{He}$ employing trinucleon wave functions calculated from modern realistic $\mathrm{NN}$ interactions (Paris, CD-Bonn). Even though the use of genuine trinucleon wave functions leads to a significant improvement over older calculations with regard to both cross section and polarization data, there are hints that polarization data with quasifree kinematics cannot be described by just two-nucleon absorption mechanisms.

The study of Coulomb excitation of ${}^{11}\mathrm{Be}$ to the first excited state in intermediate energy collisions with heavy targets is presented. The existing experimental data are reanalyzed by including the probability of projectile survival into the calculation of Coulomb excitation cross sections. The survival probabilities are calculated using a recently developed global optical model potential tailored in line with the double folding model. The extracted $B\left(E1\mathrm{}\right)\mathrm{}$ values for the transition ${\frac{1}{2}}^{+}\to {\frac{1}{2}}^{-}$ in ${}^{11}\mathrm{Be}$ are found to be slightly larger than those obtained so far using the $b_0$ recipe in Coulomb excitation theory.

Invariant mass distributions of the hadronic decay products from resonances formed in relativistic heavy-ion collision (RHIC) experiments are investigated with a view to disentangle the effects of thermal motion and the phase space of decay products from those of intrinsic changes in the structure of resonances at the freeze-out conditions. Analytic results of peak mass shifts for the cases of both equal and unequal mass decay products are derived. The shift is expressed in terms of the peak mass and width of the vacuum or medium-modified spectral functions and temperature. Examples of expected shifts in meson (e.g., $\rho ,$ $\omega ,$ and $\sigma )$ and baryon (e.g., $\Delta )$ resonances that are helpful to interpret recent RHIC measurements at BNL are provided. Although significant downward mass shifts are caused by widened widths of the $\rho$ meson in medium, a downward shift of at least 50 MeV in its intrinsic mass is required to account for the reported downward shift of 60–70 MeV in the peak of the $\rho$ invariant mass distribution. An observed downward shift from the vacuum peak value of the $\Delta$ distinctively signals a significant downward shift in its intrinsic peak mass, since unlike for the $\rho$ meson, phase space functions produce an upward shift for the $\Delta$ isobar.

We investigate the influence of new Jefferson Lab polarization-transfer ${(C}_{x^{\prime }}$ and $C_{z^{\prime }})$ and recoil polarization ${(P}_y)$ measurements in multipole fits to the single-pion photoproduction database. Results are compared to those found with the addition of a double-polarization quantity associated with the Gerasimov–Drell-Hearn sum rule.

Asymmetric nuclear matter at subsaturation densities is shown to present only one type of instability. The associated order parameter is dominated by the isoscalar density and so the transition is of liquid-gas type. The instability goes in the direction of a restoration of the isospin symmetry leading to a fractionation phenomenon. These conclusions are model independent since they can be related to the general form of the asymmetry energy. They are illustrated using density functional approaches.

New aspects of quenching of Gamow-Teller (GT) transitions and magnetic moments are investigated for p-shell nuclei using an improved shell-model Hamiltonian with enhanced spin-flip proton-neutron interaction and modified single-particle energies. The present shell-model Hamiltonian thus obtained is used in the configuration space up to (2–3)ħω excitations, and GT transitions and magnetic moments are calculated with bare g factors and bare axial-vector coupling constant. Manifestation of variable quenching due to changing gap between ${0p}_{3/2}$ and ${0p}_{1/2}$ is presented in GT transitions such as ${}^{12}{\overrightarrow{\mathrm{C}}}^{12}\mathrm{N},$ ${}^{11}{\overrightarrow{\mathrm{B}}}^{11}\mathrm{Be},$ and ${}^9{\overrightarrow{\mathrm{Li}}}^9\mathrm{Be}.$ A similar effect is shown for magnetic moments. Better agreement with experimental values is obtained systematically by using the present Hamiltonian for GT transitions and magnetic moments in most of p-shell nuclei, as well as for energy levels. Thus, the shell structure is changing from nucleus to nucleus in an orderly way (i.e., shell evolution), the inclusion of which leads us to an improved description of the GT and magnetic properties. It is stressed that the anomalous shell structure of exotic nuclei and the GT/magnetic properties of stable and exotic nuclei are linked through the same underlying mechanism.

The results of extensive coupled-reaction-channel calculations are compared with the cross section and new analyzing power data for the ${}^{12}\mathrm{C}{(}^6\mathrm{Li}{,d)}^{16}\mathrm{O}$ reaction leading to the 0.0-MeV $0^{+},$ 6.13-MeV $3^{-},$ 6.92-MeV $2^{+},$ 8.87-MeV $2^{-},$ and 10.35-MeV $4^{+}$ states of ${}^{16}\mathrm{O}$ at ${}^6\mathrm{Li}$ bombarding energies of 34 and 50 MeV. All the analyzing power data at both energies and all the cross section data at 50 MeV, with the exception of that for the ${}^{12}\mathrm{C}{(}^6\mathrm{Li}{,d)}^{16}\mathrm{O}$ transition to the 0.0-MeV $0^{+}$ state of ${}^{16}\mathrm{O}$ are presented here for the first time. These results suggest that there are significant multistep contributions to transfers leading to the $0^{+}$ and $3^{-}$ states, while those leading to the $2^{+}$ and $4^{+}$ states may be reasonably well described by simple direct $\alpha$ transfer. The importance of multistep effects is found to increase with increasing bombarding energy.

Several approximations are commonly made when studying transfer reactions with ${}^8\mathrm{B},$ in particular, those used for extracting astrophysical information. We study the influence of the spin and deformation of the ${}^7\mathrm{Be}$ nucleus on the asymptotic normalization coefficients extracted from the reaction ${}^{14}\mathrm{N}{(}^7\mathrm{Be}{,}^8\mathrm{B}{)}^{13}\mathrm{C}$ and find that it has little influence in the value of the extracted astrophysical S-factor $S_{17}\mathrm{}\left(0\right).$ We also discuss the weak continuum effects found for this reaction under the light of new breakup calculations.

We explore how nuclear modifications to the nucleon parton distributions affect production of high-$p_T$ hadrons in heavy ion collisions. We perform a leading order calculation of the high-$p_T$ charged pion, kaon, and proton spectra using standard fragmentation functions and shadowing parametrizations. We also consider alternate models of shadowing. Near midrapidity, shadowing is a small effect and cannot explain the large observed suppression of high-$p_T$ hadrons. We also consider the isospin difference between protons and nuclei and find that it is also a small effect on high-$p_T$ hadron production.

A second-order extrapolation method is presented for shell model calculations, where shell model energies of truncated spaces are well described as a function of energy variance by quadratic curves, and exact shell model energies can be obtained by the extrapolation. This new extrapolation can give more precise energy than those of first-order extrapolation method. It is also clarified that first-order extrapolation gives a lower limit of shell model energy. In addition to the energy, we derive the second-order extrapolation formula for expectation values of other observables.

It is shown that when fusion is initiated at relatively larger distances due to the presence of rotational couplings, the Businaro-Gallone barrier shifts towards higher mass asymmetry, thus favoring further mass equilibration towards symmetric configurations. This leads to the occurrence of preequilibrium fission events for all systems which affect the fission fragment angular distributions at subbarrier energies. The fission fragment angular distributions calculated as an admixture of compound nuclear and preequilibrium components explains quite well the energy dependence of the angular anisotropies for many systems around the actinide regions irrespective of the entrance channel mass asymmetries at energies both well below and above the Coulomb barrier. From the fits to the angular distributions, K-equilibration time is deduced to be $\sim 6\times {10}^{-20}$ s for a temperature $\sim 1\mathrm{MeV}.$

Angular distributions of oxygen produced in the breakup of ${}^{17}\mathrm{F}$ incident on a ${}^{208}\mathrm{Pb}$ target have been measured at angles from $75°$ to $113°$ and $39°$ to $79°$ for beam energies of 98 and 120 MeV, respectively. The data are dominated by the proton stripping mechanism and are well reproduced by dynamical calculations. The measured breakup cross section is approximately a factor of 3 less than that of fusion at 98 MeV. The influence of breakup on fusion is discussed.

As a first result of two new partial-wave analyses, one of the $\mathrm{pp}$ and another one of the $\mathrm{np}$ scattering data below 500 MeV, we report a study of the long-range chiral two-pion exchange interaction which contains the chiral coupling constants $c_1,$ $c_3,$ and $c_4.$ By using as input a theoretical value for $c_1$ we are able to determine in $\mathrm{pp}$ as well as in $\mathrm{np}$ scattering accurate values for $c_3$ and $c_4.$ The values determined from the $\mathrm{pp}$ data and independently from the $\mathrm{np}$ data are in very good agreement, indicating the correctness of the chiral two-pion exchange interaction. The weighted averages are $c_3=-4.78\left(10\right)/\mathrm{GeV}$ and $c_4=3.96\mathrm{}\left(22\right)/\mathrm{GeV},$ where the errors are statistical. The value of $c_3$ is best determined from the $\mathrm{pp}$ data and that of $c_4$ from the $\mathrm{np}$ data.

Trial wave functions including angular momentum projection and deformation with central Jastrow and linear-type correlations are calculated to study the ground state rotational band of the ${}^{20}\mathrm{Ne},$ ${}^{24}\mathrm{Mg},$ ${}^{28}\mathrm{Si},$ ${}^{32}\mathrm{S},$ and ${}^{36}\mathrm{Ar}$ nuclei and the ground state of ${}^{40}\mathrm{Ca}.$ A systematic analysis of the competition among different correlation mechanisms on the binding energy and other properties such as the root mean square radius and the transition amplitudes of the rotational band is carried out. The one- and two-body radial densities and the momentum distribution are obtained. All the calculations have been performed by means of the variational Monte Carlo method.