We introduce a particle-number reprojection method in the shell model Monte Carlo that enables the calculation of observables for a series of nuclei using a Monte Carlo sampling for a single nucleus. The method is applied to calculate nuclear level densities in the complete $\left({pf+g}_{9/2}\right)$-shell using a good-sign Hamiltonian. Level densities of odd- $A$ and odd-odd nuclei are reliably extracted despite an additional sign problem. Both the mass and the $T_z$ dependence of the experimental level densities are well described without any adjustable parameters. The odd-even staggering observed in the calculated backshift parameter follows the experimental data more closely than do empirical formulas.

It is shown that the concept of dynamical symmetry is enriched by increasing the order of the interactions between the constituent particles of a given many-body system. The idea is illustrated with an analysis of the interacting boson model of nuclei which shows that higher-order interactions can give rise to a rotational spectrum with O(6) dynamical symmetry.

The hypothesis of statistical production of $J/\psi$ mesons at hadronization is formulated and checked against experimental data. It explains in a natural way the observed scaling behavior of the $J/\psi$ to pion ratio at CERN SPS energies. Using the multiplicities of $J/\psi$ and $\eta$ mesons the hadronization temperature $T_H\approx 175\mathrm{MeV}$ is found, which agrees with the previous estimates of the temperature parameter based on the analysis of the hadron yield systematics.

Huge back-to-back correlations are shown to arise for thermal ensembles of bosonic states with medium-modified masses. The effect is experimentally observable in high energy heavy ion collisions.

An exclusive proton-proton bremsstrahlung measurement has been performed with polarized protons of 190 MeV. Absolute cross sections and analyzing powers have been measured with unprecedented accuracy in a large part of the phase space. The data are compared with state-of-the-art theoretical calculations including higher-order off-shell effects, like the $\Delta$ isobar and meson-exchange currents. Surprisingly, the calculations are unable to describe the data in detail.

The four-body equations of Alt, Grassberger, and Sandhas [Phys. Rev. C 1, 85 (1970)] are solved for a system of four nucleons, using realistic NN interactions in channels $j\le 2$. The results of the calculation are compared with data for the reactions $\mathrm{dd}\to \mathrm{dd}$, $\mathrm{dd}\to p^3\mathrm{H}$, and $n^3\mathrm{H}\to n^3\mathrm{H}$. The calculations indicate that the NN P waves have a strong effect on 4N observables including a $10\%$ contribution to the total $n^3\mathrm{H}\to n^3\mathrm{H}$ cross section at the peak of the low energy resonance.

The ${}^{12}\mathrm{C}(\alpha ,\gamma {)}^{16}\mathrm{O}$ reaction is crucial for the understanding of He burning in massive stars, but the low-energy cross section is highly uncertain. To address this problem we have measured at sub-Coulomb energies total cross sections for the ${}^{12}\mathrm{C}{(}^6\mathrm{Li},d{)}^{16}\mathrm{O}$ and ${}^{12}\mathrm{C}{(}^7\mathrm{Li},t{)}^{16}\mathrm{O}$ reactions to the bound $2^{+}$ and $1^{-}$ states of ${}^{16}\mathrm{O}$. The data are analyzed to obtain the reduced $\alpha$ widths of these states. Together with capture and phase-shift data, these results provide for a more accurate determination of the low-energy $12\mathrm{C}(\alpha ,\gamma {)}^{16}\mathrm{O}$ $S$ factor: $S_{E1\mathrm{}}\left(0.3\mathrm{MeV}\right)=101\mathrm{}\pm 17\mathrm{keV}\mathrm{b}$ and $S_{E2\mathrm{}}\left(0.3\mathrm{MeV}\right){=42\mathrm{}}_{-23\mathrm{}}^{+16\mathrm{}}\mathrm{keV}\mathrm{b}$ for the $E1\mathrm{}$ and $E2\mathrm{}$ multipole components of the reaction.

Results of nuclear resonance fluorescence experiments on ${}^{117}\mathrm{Sn}$ are reported. More than 50 $\gamma$ transitions with $E_{\gamma }<4\mathrm{}\mathrm{MeV}$ were detected. For the first time microscopic calculations making use of a complete configuration space for low-lying states are performed for a heavy odd-mass spherical nucleus. The theoretical predictions are in good agreement with the data. It is concluded that although the $E1\mathrm{}$ transitions are the strongest ones also $M1\mathrm{}$ and $E2\mathrm{}$ decays contribute substantially to the observed spectra. In contrast to the neighboring even ${}^{116–124}\mathrm{Sn}$ nuclei, in ${}^{117}\mathrm{Sn}$ the $1^{-}$ component of the two-phonon $[2_1^{+}\otimes 3_1^{-}]$ multiplet built on top of the ${1/2}^{+}$ ground state is proved to be fragmented.

Comparison of the heating effect produced by 8 $\mathrm{GeV}/c$ ${\pi }^{-}$ and antiproton beams incident on ${}^{197}\mathrm{Au}$ nuclei has been conducted with the Indiana silicon sphere $4\pi$ detector array. Event reconstruction indicates formation of thermal-like heavy residues with excitation energies up to 1.7 GeV. Enhanced energy deposition is observed for antiprotons relative to negative pions. For events with excitation energies that exceed 1000 MeV, there is a $50\%$ increase in cross section for the antiproton beam relative to the ${\pi }^{-}$ beam. The predominant decay mode at these high excitation energies is multifragmentation in which three or more $Z\ge 3$ fragments are emitted.

This paper reports high-accuracy cross-section data taken for identical kinematic conditions of the neutron-proton $\left(\mathrm{np}\right)$ and neutron-neutron $\left(\mathrm{nn}\right)$ final-state interactions in the ${}^2\mathrm{H}(n,nnp)$ reaction at an incident mean neutron energy of 13.0 MeV. These data were analyzed with rigorous three-nucleon calculations to determine the ${}^1{S}_0$ $\mathrm{np}$ and $\mathrm{nn}$ scattering lengths, $a_{\mathrm{np}}$ and $a_{\mathrm{nn}}$. Our results are $a_{\mathrm{nn}}=-18.7\mathrm{}\pm 0.6\mathrm{fm}$ and $a_{\mathrm{np}}=-23.5\mathrm{}\pm 0.8\mathrm{fm}$. The value obtained for $a_{\mathrm{nn}}$ in the present work is in agreement with that from ${\pi }^{-}d$ measurements but disagrees with values obtained from earlier neutron-deuteron breakup studies.

The magnetic moment of ${}^{11}\mathrm{Be}$ ( $T_{1/2}=13.8\mathrm{s}$) was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a ${}^{11}{\mathrm{Be}}^{+}$ ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal, and observation of rf resonances in the asymmetric angular distribution of the $\beta$ decay ( $\beta$-NMR). The nuclear magnetic moment $\mu {(}^{11}\mathrm{Be})=-1.6816\mathrm{}(8){\mu }_N$ provides a stringent test for theoretical models describing the structure of the $1/2^{+}$ neutron halo state.

Differential cross sections for the $\gamma p\to {\pi }^{+}n$ reaction have been measured at photon energies 1 to 2 MeV above threshold using tagged-photon beams. The electric dipole amplitude $E_{0+}$ deduced at threshold is compared to recent predictions from chiral perturbation theory. Constraints on the value of the $\pi N$ coupling constant are inferred by combining theory and experiment.

The particle-hole excitations through the $N=40\mathrm{}$ subshell around ${}^{68}\mathrm{Ni}$ have been studied by the $\beta$ decay of ${}^{69}\mathrm{Co}$ and ${}^{69}\mathrm{Ni}$. The half-life of ${}^{69}\mathrm{Co}$ was measured to be 0.22(2) s, and a new $\beta$-decaying isomer with a half-life of 3.5(5) s was identified in ${}^{69}\mathrm{Ni}$. From the decay of the ${}^{69}\mathrm{Ni}$ isomer a 9(4)% mixing of the $\pi p_{3/2}^{+1\mathrm{}}\nu p_{1/2}^{-2\mathrm{}}\nu g_{9/2}^{+2\mathrm{}}$ configuration into the ground state of ${}^{69}\mathrm{Cu}$ can be deduced. Significant polarization of the ${}^{68}\mathrm{Ni}$ core nucleus is observed with the coupling of a single nucleon, which implies a rapid decrease in the stabilizing effect of the $N=40\mathrm{}$ semimagic shell gap.

Information entropy and Zpif's law in the field of information theory have been used for studying the disassembly of nuclei in the framework of the isospin dependent lattice gas model and the molecular dynamical model. We found that the information entropy in the event space is maximum at the phase transition point and the mass of the cluster shows exactly inversely to its rank, i.e., Zpif's law appears. Both novel criteria are useful in searching the nuclear liquid gas phase transition experimentally and theoretically.

The behavior of the nuclear matter response in the region of large momentum transfer, in which plane wave impulse approximation predicts the onset of $y$ scaling, is discussed. The theoretical analysis shows that scaling violations produced by final state interactions are driven by the momentum dependence of the nucleon-nucleon scattering cross section. Their study may provide valuable information on possible modifications of nucleon-nucleon scattering in the nuclear medium.

We study the expansion dynamics of a quark-antiquark plasma droplet from an initial state with restored chiral symmetry. The calculations are made within the linear $\sigma$ model scaled with an additional scalar field representing the gluon condensate. We solve numerically the classical equations of motion for the meson fields coupled to the fluid-dynamical equations for the plasma. Strong space-time oscillations of the meson fields are observed in the course of the chiral transition. A new phenomenon, the formation and collapse of vacuum bubbles, is predicted. The particle production due to the bremsstrahlung of the meson fields is estimated.

The prospect of using $\Lambda p$ correlations to extract source sizes in relativistic heavy ion collisions is investigated. It is found that the strong interaction induces a large peak in the correlation function that provides more sensitive source size measurements than $\mathrm{pp}$ correlations under some circumstances. The prospect of using $\Lambda p$ correlations to measure the time lag between lambda and proton emissions is also studied.

Based on realistic calculations for the nonmesonic decay rate of ${}_{\Lambda }^3\mathrm{H}$ we demonstrate that, in principle, it is not possible to measure the total $n$- and $p$-induced decay rates and as a consequence ${\Gamma }_n/{\Gamma }_p$ for that lightest hypernucleus. The calculations are performed with modern $\mathrm{YN}$ forces based on various meson exchanges and taking the final state interaction among the three nucleons fully into account. Our findings might have consequences also for the interpretation of experimental ${\Gamma }_n/{\Gamma }_p$ ratios for heavier hypernuclei where severe discrepancies exist to theoretical ${\Gamma }_n/{\Gamma }_p$ ratios.

The ${}^{16}\mathrm{O}(\gamma ,pn)$ reaction was measured at $E_{\gamma }\sim 72\mathrm{MeV}$ with resolution sufficient to distinguish the low-lying states of the residual ${}^{14}\mathrm{N}$ nucleus. Cross sections averaged over the acceptance of the detector system were determined for each of the resolved states. The relative population of residual states indicates that proton-neutron pairs coupled to $(J^{\pi },T)=(0^{+},1\mathrm{})$ play a minor role in the photon absorption process compared to $(1^{+},0\mathrm{})$ pairs and that both $L=0\mathrm{}$ and $L=2\mathrm{}$ pairs participate in the reaction.