The spin-flavor structure of certain nucleon-nucleon scattering observables derived from the large-$N_c$ limit of QCD in the kinematical regime where time-dependent mean-field theory is valid is discussed. In a previous work [T.D. Cohen and B.A. Gelman, Phys. Lett. B 540, 227 (2002)], this regime was taken to be where the external momentum was of the order of $N_c$ which precluded the study of differential cross sections in elastic scattering. Here it is shown that the regime extends down to the order of $N_c^{1/2}$ which includes the higher end of the elastic regime. The prediction is that in the large-$N_c$ limit, observables describable via mean-field theory are unchanged when both the spin and isospin of either nucleon are flipped. This prediction is tested for proton-proton and neutron-proton elastic scattering data and found to fail badly. We argue that this failure can be traced to a lack of a clear separation of scales between momentum of the order of $N_c^{1/2}$ and $N_c^1$ when $N_c$ is as small as three. The situation is compounded by an anomalously low particle production threshold due to approximate chiral symmetry.

The excitation region in ${}^{12}\mathrm{C}$ below $E_x=45\mathrm{}\mathrm{MeV}$ was studied using 240 MeV α-particle scattering. Elastic scattering was measured from ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=3.8\mathrm{}°$ to 49.4° and density dependant folding optical model parameters were obtained. Inelastic scattering to the 4.44 MeV $2^{+},$ 7.65 MeV $0^{+},$ 9.64 MeV $3^{-},$ 10.3 MeV $0^{+},$ and 10.84 MeV $1^{-}$ states was measured and $B\left(\mathrm{EL}\right)\mathrm{}$ values obtained. Inelastic scattering exciting ${}^{12}\mathrm{C}$ to $10\mathrm{MeV}<~E_x<~12.5\mathrm{MeV}$ was measured from $1.4°<~{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~10°$ and to $12.5\mathrm{MeV}<~E_x<~45\mathrm{MeV}$ from $1.4°<~{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<~16°$ and $E0,$ $E1,$ $E2,$ and $E3\mathrm{}$ strength distributions were obtained. Strength was identified corresponding to 27±5, 78±9, and 51±7% of the isoscalar $E0,$ $E1,$ and $E2\mathrm{}$ energy weighted sum rule (EWSR), respectively, with centroids of 21.9±0.3, 27.5±0.4, and 22.6±0.5 MeV and rms widths of 4.8±0.5, 7.6±0.6, and 6.8±0.6 MeV. Less than 7% of the $E3\mathrm{}$ EWSR strength was identified.

We have measured the probability of double K-shell vacancy production in the electron capture decay of ${}^{54}\mathrm{Mn}$ to the 835-keV level of ${}^{54}\mathrm{Cr}.$ The probability was deduced from the number of triple coincidences among the Cr hypersatellite and satellite x rays emitted in filling the double vacancy and the 835-keV $\gamma$ ray. The probability of double K-shell vacancy production per K-shell electron capture ${(P}_{\mathrm{KK}})$ was found to be ${(2.3\mathrm{}}_{-0.5}^{+0.8\mathrm{}})\times {10}^{-4}.$ Comparisons to previous experimental results and theoretical calculations are discussed.

Reduced electric quadrupole decay strengths, $B\left(E2\mathrm{}\right),$ of even ${}^{110-120}\mathrm{Cd}$ isotopes have been calculated using a recently developed theoretical framework suited for dynamical microscopic description of two-phonon-like states and their energy splitting due to interaction with low-lying one-phonon states. This model starts from a realistic single-particle valence space and a microscopic many-body Hamiltonian, which is used to generate the one-phonon states by the use of the Quasiparticle Random-Phase Approximation. The anharmonic vibrational effects, contained in the calculated energies and $B\left(E2\mathrm{}\right)\mathrm{}$ values, have been studied along the ${}^{110-120}\mathrm{Cd}$ chain of isotopes. Comparison of the calculated energies and $B\left(E2\mathrm{}\right)\mathrm{}$ values with data points to mixing between anharmonic vibrations and deformed intruder degrees of freedom.

The liquid-gas phase transition and associated instability in two component systems are investigated using a mean field theory. The importance of the roles of both the Coulomb force and the symmetry energy terms are studied. The addition of the Coulomb terms brings asymmetry into a mean field interaction and thus results in important differences with previous approaches, which did not include such terms. The asymmetric Coulomb effects modify the chemical instability and mechanical instability domains shifting many features, such as the line of equal concentration and the contact line of chemical and mechanical instability boundary, away from proton fraction point $y=1/2\mathrm{}$ to a value closer to the valley of $\beta$ stability. Thus, isospin fractionization is somewhat moderated by the presence of the Coulomb force. These features and characteristics of phase transition away from $\beta$ stability are discussed in detail.

Fusionlike events in ${}^{58}\mathrm{Ni}{+}^{12}\mathrm{C}$ at 34.5 MeV/nucleon are isolated by use of the statistical discriminant analysis method applied to a set of 20 global variables in complete events with at least 90% of the total charge of the system. Two-fragment reduced-velocity correlation functions are measured for the emission of intermediate mass fragments (IMF’s) and compared to many-body trajectory calculations. Alpha particle emission sequence has been deduced as a function of excitation energy. At the highest excitations, $\alpha$ particles are emitted simultaneously with IMF’s on a time scale of about $200–300\mathrm{fm}/c.\mathrm{}$ In less excited events, they are emitted on a longer time scale. This hybrid deexcitation mechanism, sequential and prompt, is corroborated by comparing the charge of the heaviest and the second heaviest fragments to predictions of GEMINI and SMM simulations.

The decay of ${}^{56}{\mathrm{Ni}}^{*},$ formed in ${}^{32}\mathrm{S}{+}^{24}\mathrm{Mg}$ reaction at the incident energies $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=51.6\mathrm{}$ and 60.5 MeV (where c.m. is the center of mass), is calculated as a cluster decay process within the preformed cluster-decay model of Gupta et al. [Phys. Rev. C 65, 024601 (2002)] reformulated for hot compound systems. Interestingly enough, the cluster decay process is shown to contain the complete structure of both the measured fragment cross sections and total kinetic energies (TKEs). The observed deformed shapes of the exit channel fragments are simulated by introducing the neck-length parameter at the scission configuration, which nearly coincides with the ${}^{56}\mathrm{Ni}$ saddle configuration. This is the only parameter of the model, which, though, is also defined in terms of the binding energy of the hot compound system and the ground-state binding energies of the various emitted fragments. For the temperature effects included in shell corrections only, the normalized $\alpha$-nucleus s-wave cross sections calculated for nuclear shapes with outgoing fragments separated within nuclear proximity limit (here $\sim 0.3\mathrm{fm})$ can be compared with the experimental data, and the TKEs are found to be in reasonably good agreement with experiments for the angular momentum effects added in the sticking limit for the moment of inertia. The incident energy effects are also shown in predicting different separation distances and angular momentum values for the best fit. Also, some light particle production (other than the evaporation residue, not treated here) is predicted at these energies and, interestingly, ${}^4\mathrm{He},$ which belongs to evaporation residue, is found missing as a dynamical cluster-decay fragment. Similar results are obtained for temperature effects included in all the terms of the potential energy. The non-$\alpha$ fragments are now equally important, and hence present a more realistic situation with respect to experiments.

This paper constructs relativistic quantum mechanical models of particles satisfying cluster properties and the spectral condition which do not conserve particle number. The treatment of particle production is limited to systems with a bounded number of bare-particle degrees of freedom. This paper focuses on the realization of cluster properties in these theories.

We discuss the spin dependence of the effective two-body interactions appropriate for three-body computations. The only reasonable choice seems to be the fine and hyperfine interactions known for atomic electrons interacting with the nucleus. One exception is the nucleon-nucleon interaction imposing a different type of symmetry. We use the two-neutron halo nucleus ${}^{11}\mathrm{Li}$ as an illustration. We demonstrate that models with the wrong spin dependence are basically without predictive power. The Pauli forbidden core and valence states must be consistently treated.

To explore the effects of higher order coupling on the barrier distribution, we have measured the quasielastic excitation function for ${}^{12}\mathrm{C}{+}^{142}\mathrm{Nd}$ around the nominal Coulomb barrier from 44 to 58 MeV in steps of 1 MeV. Theoretical coupled channel calculations with one and two phonon states were performed using the code ECIS94. The analysis showed that the second order coupling effects explained the barrier distribution profile and excitation function more appropriately than the first order couplings.

We examine flavor SU(3) breaking effects on meson-baryon scattering amplitudes in the chiral unitary model. It turns out that the SU(3) breaking, which appears in the leading quark mass term in the chiral expansion, cannot explain the channel dependence of the subtraction parameters of the model, which are crucial for reproducing the observed scattering amplitudes and resonance properties.

Using relations between wave functions obtained in the framework of the relativistic mean field theory, we investigate the effects of pseudospin and spin symmetry breaking on the single nucleon wave functions in spherical nuclei. In our analysis, we apply both relativistic and nonrelativistic self-consistent models as well as the harmonic oscillator model.

Using an isospin-dependent transport model, we study isospin effects on two-nucleon correlation functions in heavy-ion collisions induced by neutron-rich nuclei at intermediate energies. We find that these correlation functions are sensitive to the density dependence of nuclear symmetry energy, but not to the incompressibility of symmetric nuclear matter and the medium dependence of nucleon-nucleon cross sections. This sensitivity is mainly due to effects of nuclear symmetry energy on the emission times of neutrons and protons as well as their relative emission sequence. We also study the variations of the symmetry energy effects on nucleon-nucleon correlations with respect to the impact parameter, incident energy, and mass number of heavy-ion collisions.

A schematic model of overdamped motion is presented which permits one to calculate the mean first passage time for nuclear fission. Its asymptotic value may exceed considerably the lifetime suggested by Kramers rate formula, which applies only to very special, favorable potentials and temperatures. The additional time obtained in the more general case is seen to allow for a considerable increment in the emission of light particles.

We consider a soluble model of multifragmentation which is similar in spirit to many models which have been used to fit intermediate energy heavy ion collision data. In this model, $c_v$ is always positive but for finite nuclei $c_p$ can be negative for some temperatures and pressures. Furthermore, negative values of $c_p$ can be obtained in canonical treatment. One does not need to use the microcanonical ensemble. Negative values for $c_p$ can persist for systems as large as 200 particles but this depends upon parameters used in the model calculation. As expected, negative specific heats are absent in the thermodynamic limit.

We study the propagation properties of the $\rho$ vector in a dense and hot pion medium. We introduce a finite value of the chemical potential associated with a conserved pion number and argue that such description is valid during the hadronic phase of a relativistic heavy-ion collision, between chemical and thermal freeze-out, where the strong interaction drives pion number to a fixed value. By invoking vector dominance and $\rho$ saturation, we also study the finite pion density effects into the low mass dilepton production rate. We find that the distribution moderately widens and the position of the peak shifts toward larger values of the pair invariant mass, at the same time that the height of the peak decreases when the value of the chemical potential grows. We conclude by arguing that for the description of the dilepton spectra at ultrarelativistic energies, such as those of Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC), the proper treatment of the large pion density might be a more important effect to consider than the influence of a finite baryon density.

In this work we study the warm equation of state of asymmetric nuclear matter in the quark-meson coupling model which incorporates explicitly quark degrees of freedom, with quarks coupled to scalar, vector, and isovector mesons. Mechanical and chemical instabilities are discussed as a function of density and isospin asymmetry. The binodal section, essential in the study of the liquid-gas phase transition is also constructed and discussed. The main results for the equation of state are compared with two common parametrizations used in the nonlinear Walecka model and the differences are outlined.

We calculate a $\Lambda \Lambda$ pairing gap in binary mixed matter of nucleons and $\Lambda$ hyperons within the relativistic Hartree-Bogoliubov model. $\Lambda$ hyperons to be paired up are immersed in background nucleons in a normal state. The gap is calculated with a one-boson-exchange interaction obtained from a relativistic Lagrangian. It is found that at background density ${\rho }_N=2.5\mathrm{}{\rho }_0$ the $\Lambda \Lambda$ pairing gap is very small, and that a denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density. An effect of weaker $\Lambda \Lambda$ attraction on the gap is also examined in connection with the revised information of the $\Lambda \Lambda$ interaction.