Microcanonical caloric curves at constant pressure and pressure versus volume curves at constant temperature are calculated using the probability distributions of a canonical ensemble at constant pressure. It is evidenced that the constant pressure path provides a natural order parameter even for small systems. While for large systems the Coulomb interaction is destroying the liquid-gas phase transition, for smaller systems the phase transition survives. Phase diagrams of a nuclear system without Coulomb and hard-core interactions are constructed and the critical point is identified.

High-angular-momentum states in ${}^{108}\mathrm{Cd}$ were populated via the ${}^{64}\mathrm{Ni}{(}^{48}\mathrm{Ca},4n)$ reaction at a beam energy of 207 MeV. Gamma rays were detected using the Gammasphere array. A rotational band has been observed with a dynamic moment of inertia and deduced lower limit of the quadrupole moment suggesting a major-to-minor axis ratio larger than 1.8:1, placing it among the most deformed structures identified in any nucleus, to date.

The excitation function of the reaction ${}^{22}\mathrm{Ne}(\alpha ,n{)}^{25}\mathrm{Mg}$, the key neutron source in the astrophysical $s$ process in massive stars, has been determined from threshold at $E_{\alpha }=570\mathrm{}$ up to 1450 keV with an experimental sensitivity of ${10}^{-11\mathrm{}}\mathrm{b}$. For all resonances in this energy range new resonance parameters have been measured. For a possible resonance at about 635 keV a new upper limit $\omega \gamma <60\mathrm{}\mathrm{neV}$ for the strength was obtained. Based on the new data, improved reaction rates were calculated as a function of temperature. The new uncertainty limits are considerably smaller than in previous determinations, ruling out the large enhancement factors, up to 500, assumed in some stellar model calculations.

The early stages of a relativistic heavy-ion collision are examined in the framework of an effective classical SU(3) Yang-Mills theory in the transverse plane. We compute the initial energy and number distributions, per unit rapidity, at midrapidity, of gluons produced in high-energy heavy-ion collisions. We discuss the phenomenological implications of our results in light of the recent Relativistic Heavy-Ion Collider data.

Separated longitudinal and transverse cross sections for charged pion electroproduction from ${}^1\mathrm{H}$, ${}^2\mathrm{H}$, and ${}^3\mathrm{He}$ were measured at $Q^2=0.4\mathrm{}(\mathrm{GeV}/c{)}^2$ for two values of the invariant mass, $W=1.15\mathrm{}\mathrm{GeV}$ and $W=1.60\mathrm{}\mathrm{GeV}$, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in ${}^3\mathrm{He}$ at $W=1.60\mathrm{}\mathrm{GeV}$. The $W=1.15\mathrm{}\mathrm{GeV}$ results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.

We derive the major characteristics of inclusive and diffractive final states in deep-inelastic scattering off heavy nuclei for the high-energy (small- $x$) kinematics in which the limit of complete absorption is reached for the dominant hadronic fluctuations in the virtual photon (the black-body limit of the process). Both the longitudinal and transverse distributions of the leading hadrons are found to be strikingly different from the corresponding ones within the leading-twist approximation, and hence provide unambiguous signals for the onset of the black-body limit.

A new $\alpha$-cluster wave function is proposed which is of the $\alpha$-particle condensate type. Applications to ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ show that states of low density close to the 3 and 4 $\alpha$-particle thresholds in both nuclei are possibly of this kind. It is conjectured that all self-conjugate $4n$ nuclei may show similar features.

Recent results from Au+Au collisions at BNL RHIC energy hint at explosive hadron production at the QCD transition rather than soft hydrodynamic evolution. We speculate that this is due to a rapid variation of the effective potential for QCD close to $T_c$. Performing real-time lattice simulations of an effective theory we show that the fast evolution of the potential leads to “explosive” spinodal decomposition rather than bubble nucleation or critical slowing down.

We estimate the dipole radiation emitted in fusion processes. We show that a classical bremsstrahlung approach can account for both the preequilibrium and the thermal photon emission. We give an absolute evaluation of the preequilibrium component due to the charge asymmetry in the entrance channel, and we study the energy and mass dependence in order to optimize the observation. This dynamical dipole radiation could be a relevant cooling mechanism in the fusion path. We stress the interest in experiments with the new available radioactive beams.

We report first results on elliptic flow of identified particles at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=130\mathrm{}\mathrm{GeV}$ using the STAR TPC at RHIC. The elliptic flow as a function of transverse momentum and centrality differs significantly for particles of different masses. This dependence can be accounted for in hydrodynamic models, indicating that the system created shows a behavior consistent with collective hydrodynamical flow. The fit to the data with a simple model gives information on the temperature and flow velocities at freeze-out.

We apply the ab initio no-core nuclear shell model to solve the six-nucleon systems, ${}^6\mathrm{Li}$ and ${}^6\mathrm{He}$, interacting by realistic nucleon-nucleon ( $\mathrm{NN}$) potentials. In particular, we present the first results for $A=6\mathrm{}$ with the nonlocal CD-Bonn $\mathrm{NN}$ potential. The resulting ${}^6\mathrm{Li}$ binding energy $-29.3\mathrm{}\left(6\right)\mathrm{MeV}$ and the excitation spectra improve the agreement between the theory and experiment compared to results with local $\mathrm{NN}$ potentials, but the need for the inclusion of a real three-body interaction and/or further improvement of the $\mathrm{NN}$ forces remains. We predict properties of the ${}^6\mathrm{He}$ dipole modes, a subject of current controversy.

The intrinsic quadrupole moment $Q_0$ of superdeformed rotational bands in $A\sim 150$ nuclei depends on the associated single-particle configuration. We have derived an empirical formula based on the additivity of effective quadrupole moments of single-particle orbitals that describes existing measurements from ${}^{142}\mathrm{Sm}$ to ${}^{152}\mathrm{Dy}$. To further test the formula, the predicted $Q_0$ moments for two superdeformed bands in ${}^{146}\mathrm{Gd}$ of $14.05e\mathrm{b}$ were confronted with a new measurement yielding $13.9\pm 0.4e\mathrm{b}$ and $13.9\pm 0.3e\mathrm{b}$, respectively. This excellent agreement provides empirical evidence of extreme single-particle behavior in highly deformed, collective systems.

We analyze the recent experimental data on photofissility for ${}^{237}\mathrm{Np}$, ${}^{238}\mathrm{U}$, and ${}^{232}\mathrm{Th}$ at incident photon energies above $200\mathrm{MeV}$. For this analysis, we developed a Monte Carlo algorithm for the nuclear evaporation process in photonuclear reactions. This code is used in association with the multicollisional model for the photon-induced intranuclear cascade process. Our results show a good quantitative and qualitative agreement with the experimental data. It is shown that the emission of protons and alpha particles at the evaporation stage is an important component for the nonsaturation of actinide photofissility up to, at least, 1 GeV.

Given a single $j$-shell Hamiltonian, the algebraic conditions for conservation of seniority are derived from a quasispin tensor decomposition of the two-nucleon interaction. This makes it possible to construct useful solvable and partially solvable shell-model Hamiltonians with eigenstates classified by a spectrum generating algebra. Applications are made to the low-lying energy levels of the $N=50\mathrm{}$ nuclear isotones.

Measurements of the ${}^2\mathrm{H}\left(\overrightarrow{e}{,e}^{\prime }p\right)n$ reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, $f_{\mathrm{LT}}$ and $f_{\mathrm{LT}}^{\prime }$, and the transverse-transverse, $f_{\mathrm{TT}}$, interference responses at a missing momentum of $210\mathrm{MeV}/c$ were simultaneously extracted in the dip region at $Q^2=0.15(\mathrm{GeV}/c{)}^2$. In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.

We examine a quantum phase transition in $\gamma$-soft nuclei, where the O(6) limit is simultaneously a dynamical symmetry of the U(6) group of the interacting boson model and a critical point of a prolate-oblate phase transition. This is the only example of phase transitional behavior that can be described analytically for a finite $s,d$ boson system.

The energy derived from the CN cycle at low stellar temperatures is regulated by the ${}^{14}\mathrm{N}(p,\gamma {)}^{15}\mathrm{O}$ reaction. A previous direct measurement of this reaction has been interpreted as showing evidence for a subthreshold resonance which makes a major contribution to the reaction rate at low temperatures. This resonance, at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=-504\mathrm{}\mathrm{keV}$ would correspond to the known $E_x=6793\mathrm{}-\mathrm{keV}$ state in ${}^{15}\mathrm{O}$. We have measured a mean lifetime of ${1.60}_{-0.72\mathrm{}}^{+0.75\mathrm{}}\mathrm{fs}$ $(90\%\mathrm{C}.\mathrm{L}.\mathrm{})$ for this state using the Doppler-shift attenuation method. This lifetime is a factor of 15 longer than that inferred from the $(p,\gamma )$ data and implies that the contribution of the subthreshold resonance is negligible.

We introduce generalized quark and gluon distributions in the deuteron, which can be measured in exclusive processes like deeply virtual Compton scattering and meson electroproduction. We discuss the basic properties of these distributions and point out how they probe the interplay of nucleon and parton degrees of freedom in the deuteron wave function.

Stimulated gluon emission and thermal absorption, in addition to induced radiation, are considered for an energetic parton propagating inside a quark-gluon plasma. In the presence of thermal gluons, stimulated emission reduces, while absorption increases, the parton's energy. The net effect is a reduction of the parton energy loss. Though decreasing asymptotically as $T/E$ with the parton energy, the relative reduction is found to be important for intermediate energies. The modified energy dependence of the energy loss will affect the shape of suppression of moderately high $p_T$ hadrons due to jet quenching in high-energy heavy-ion collisions.

Spins and parities of high spin states above the particle-binding threshold in ${}^{24}\mathrm{Mg}$ were determined with a basis expansion technique using triple and quadruple angular correlations between $\alpha$ particles and $\gamma$ rays. The first unambiguous identification of a ${10}^{+}$ state is reported. Located at 19.2(1) MeV, this state decays predominantly by $\alpha$ emission, although a candidate $\gamma$-decay branch with a 5.927 MeV transition connecting this ${10}^{+}$ level to the rotational $8^{+}$ state at 13.2 MeV was identified as well. The corresponding $\gamma -\alpha$ branching ratio is $7\left(3\right)\times {10}^{-4\mathrm{}}$.