The diffractive hadron-nucleus cross sections are evaluated in a model where the exchanged strings fuse if they are close in the impact parameter space. The resulting total diffractive cross sections are larger than in the Glauber model. The cross sections for the inelastic dissociation of the nucleus are much smaller than in Glauber-like models and reasonably agree with the experimental data.

The momentum dependence of the off-shell ρ-ω mixing amplitude is calculated through a two-quark loop diagram, using nonperturbative meson-quark vertex functions for the ρ and ω mesons, as well as nonperturbative quark propagators. Both these quantities are generated self-consistently through an interlinked Bethe-Salpeter equation (BSE) cum Schwinger- Dyson equation (SDE) approach with a 3D support for the BSE kernel with two basic constants that are prechecked against a wide cross section of both meson and baryon spectra within a common structural framework for their respective 3D BSE’s. With the precalibration, the on-shell strength works out at -2.434 δ(${\mathit{m}}_{\mathit{q}}^2$) in units of the change in ‘‘constituent mass squared,’’ which is consistent with the ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ to ${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ data for a u-d mass difference of 4 MeV, while the relative off-shell strength (0.99±0.01) lies midway between quark-loop and QCD-SR results. We also calculate the photon-mediated ρ-ω propagator whose off-shell structure has an additional pole at ${\mathit{q}}^2$=0. The implications of these results vis-a-vis related investigations are discussed.

The quark delocalization and color screening model, a quark potential model, is used for a systematic search of dibaryon candidates in the u, d, and s three flavor world. Color screening, which appears in unquenched lattice gauge calculations, and quark delocalization (which is similar to electron delocalization in molecular physics) are both included. Flavor symmetry breaking and channel coupling effects are studied. The model is constrained not only by baryon ground state properties but also by the N-N scattering phase shifts. The deuteron and zero energy dinucleon resonance are both reproduced qualitatively. The model predicts two extreme types of dibaryonic systems: ‘‘molecular’’ like the deuteron, and highly delocalized six-quark systems among which only a few narrow dibaryon resonances occur in the u, d, and s three flavor world. Possible high spin dibaryon resonances are emphasized.

The short range correlation effect on the pion propagator is studied in two ways. We emphasize the comparison between our new formalism and the old formalism. Analytical expressions for the relativistic particle-hole excitation of the pion propagator are obtained, they are used to compute the real and the imaginary part of the polarization insertion including a short range correlation effect, and a pion dispersion relation. A pole is found on the polarization insertion derived in the old formalism, this pole also truncates the dispersion relation curves. The pionic acoustic sound branch, or pion condensation is suppressed by the short range correlation in both formalisms.

The momentum-space cutoff parameter Λ of hadronic vertex functions is studied in this paper. We use a composite model where we can measure the contributions of intermediate particle propagations to Λ. We show that in many cases a composite vertex function has a much smaller cutoff than its constituent vertices, particularly when light constituents such as pions are present in the intermediate state. This suggests that composite meson-baryon-baryon vertex functions are rather soft, i.e., they have Λ considerably less than 1 GeV. We discuss the geometrical origin of this softening of form factors as well as the implications of our findings on the modeling of nuclear reactions.

The Glauber approximation is used to calculate the contribution of nucleon correlations in high-energy A(e,e’N) reactions. When the excitation energy of the residual nucleus is small, the increase of the nuclear transparency due to correlations between the struck nucleon and the other nucleons is mostly compensated by a decrease of the transparency due to the correlations between nondetected nucleons. We derive Glauber model predictions for nuclear transparency for the differential cross section when nuclear shell level excitations are measured. The role of correlations in color transparency is briefly discussed.

We employ a relativistic quark bag picture, the chromodielectric soliton model, to discuss the quarks’ symmetry structure and momentum distribution in the N-N system. Six-quark clusters are constructed in a constrained mean-field calculation. The corresponding Hamiltonian contains not only an effective interaction between the quarks and a scalar field, which is assumed to parametrize all nonperturbative effects due to the nonlinearity of QCD, but also quark-quark interactions mediated through one-gluon exchange. We also evaluate the quark light-cone distribution functions, characterizing inclusive deep-inelastic lepton scattering, for the nucleon as well as for the six-quark structures. We find a competition between a softening of the quarks’ momenta through the increase of the confinement volume, and a hardening via the admixture of higher symmetry configurations due to the color-electrostatic one-gluon exchange. These findings suggest an unexpected absence of many-nucleon, multiquark effects, even though six-quark structures should represent a nonnegligible part of the nuclear ground state.

Using the general framework of quantum field theory, we derive basic equations of quantum field kinetics. The main goal of this approach is to compute the observables associated with a quark-gluon plasma at different stages of its evolution. We start by rewriting the integral equations for the field correlators in different forms, depending on the relevant dynamical features at each different stage. Next, two versions of perturbation expansion are considered. The first is best suited for the calculation of electromagnetic emission from chaotic, but not equilibrated, strongly interacting matter. The seocnd version allows one to derive evolution equations, which are generalizations of the familiar QCD evolution equations, and provide a basis for the calculation of the initial quark and gluon distributions after the first hard interaction of the heavy ions.

The stellar (n,γ) cross section of the comparably short-lived isotope ${}_{}{}^{155}{}_{}{}^{}\mathrm{Eu}$ (${\mathit{t}}_{1/2}$=4.96 yr) has been experimentally determined relative to that of gold by means of the activation method. A sample containing only 3.4×${10}^{14}$ ${}_{}{}^{155}{}_{}{}^{}\mathrm{Eu}$ atoms was irradiated for 17 days in a quasistellar neutron spectrum corresponding to a thermal energy of kT=25 keV. The cross section obtained from the induced activity yields a value of 〈σ×v〉/${\mathit{v}}_{\mathit{T}}$=1320±80 mb at kT=30 keV. This result is of relevance for analyzing the abundance pattern in the s-process branchings at A=151, 152, and 154 with respect to the temperature during helium shell burning in low mass stars.

At very low energies of astrophysical interest, the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$(p,γ${)}^8$B reaction is almost totally peripheral. Consequently, the overall normalization of the cross section for this reaction is defined by the asymptotic normalization coefficient of the bound-state wave function of ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ in the two-body channel ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$+p. The reaction ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$${(}^3$He,d${)}^8$B is suggested as a tool to measure this asymptotic normalization coefficient thereby allowing one to define the absolute value of the astrophysical factor, ${\mathit{S}}_{17}$(0), for the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$(p,γ${)}^8$B reaction.

We have measured the coincidence d(e→,e′p) reaction in quasielastic scattering, detecting the proton in a noncoplanar geometry. The electron helicity asymmetry ${\mathrm{A}}_{\mathrm{e}}$ and the imaginary part of the longitudinal-transverse interference structure function ${\mathrm{f}}_{\mathrm{LT}}^{\prime }$ have been determined at a four-momentum transfer ${\mathrm{Q}}^2$=3.3 ${\mathrm{fm}}^{\mathrm{-}2}$. The results are compared with theoretical calculations which use realistic potentials for the NN interaction.

We have determined the spectroscopic quadrupole moment of two high-spin isomers (I=11 ħ and I=32 ħ) which have recently been identified in the doubly-odd ${}_{}{}^{214}{}_{}{}^{}\mathrm{Fr}$ nucleus. The data have been extracted from a series of former level mixing spectroscopy (LEMS) measurements which had been performed to measure quadrupole moments of high-spin isomers in ${}_{}{}^{211,212,213}{}_{}{}^{}\mathrm{Fr}$ isotopes. The quadrupole frequencies were measured in natural and enriched poly- and single-crystalline T1 at different temperatures.

We measure the mass of the lowest T=2 state in ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ by observing β-delayed protons following the superallowed ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ca}$ decay and use this result to make a precise test of the isobaric multiplet mass equation.

Reduced-velocity correlation functions between two and three intermediate mass fragments are compared for central ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Ar collisions at E/A=50 MeV. Previously published N-body Coulomb-trajectory calculations, capable of reproducing the measured two-fragment reduced velocity-correlation function, describe the measured three-fragment correlation function equally well. Moreover, ambiguities between source size and lifetime observed in the analysis of two-fragment correlations remain unresolved in the three-fragment correlation function.

Light charged particle emission has been investigated as a function of excitation energy in exclusive experiments on the decay of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ projectiles between 25A and 70A MeV. The systematics of excitation energy removed by Z=1 and Z=2 particles were deduced. The results are similar to a previous study of proton and α-particle evaporation in compound nucleus reactions at beam energies below 20A MeV, supporting the idea of a common statistical process.

Absolute cross sections of (γ,n) transitions in lead, bismuth, and terbium were measured using thermal neutron capture photons, and a high resolution neutron spectrometer. The measured (γ,n) cross sections were compared with predictions of the Direct-Semi-Direct (DSD) and the compound nucleus (CN) models, and were found to be generally underestimated by the DSD calculations and closer to the predictions of the CN models. Some of the (γ,n) cross sections in lead and bismuth were found to be comparable in magnitude to the extrapolation from the tail of the giant dipole resonance.

The reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^{16}$O,7α) has been studied over the center-of-mass energy range from 37.7 MeV to 51.4 MeV, in a search for evidence for a 7-α chain state in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. The yields of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($0_2^{+}$)${\mathrm{-}}^{12}$C($0_2^{+}$)-α and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($0_2^{+}$)${\mathrm{-}}^8$Be${\mathrm{-}}^8$Be final states agree broadly with previous measurements but contain no structure, indicating that a ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ chain state is probably not being observed. The yields for the inelastic scattering reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{16}$O decaying to other excited states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ have also been studied. They also contain no gross structure.

It has been suggested that the resonance found at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=32.5 MeV in an inelastic channel of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C corresponds to a six alpha-particle chain state. Reexamining our earlier data on this system a resonance is observed at the same energy in another outgoing channel, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^8$Be, which is not expected to resonate for such a configuration. We observe similar angular distributions but an appreciably narrower width than that measured in the inelastic channel.

In this paper the behavior of factorial moments with rapidity window size, which is usually explained in terms of ‘‘intermittency,’’ has been interpreted by simple quantum statistical properties of the emitting system using the concept of ‘‘modified two-source model’’ as recently proposed by Ghosh and Sarkar [Phys. Lett. B 278, 465 (1992)]. The analysis has been performed using our own data of ${}_{}{}^{16}{}_{}{}^{}\mathrm{Ag}$/Br and ${}_{}{}^{24}{}_{}{}^{}\mathrm{Ag}$/Br interactions at a few tens of GeV energy regime.

We use linear energy-weighted sum rules within the proton-neutron interacting boson model to deduce a relationship between magnetic dipole and magnetic octupole transition probabilities. We then obtain a first estimate of the summed magnetic octupole strength to be expected in rare-earth nuclei.