This paper contains new developments of the Bonaccorso-Brink reaction model for neutron transfer to continuum states in heavy-ion collisions. The spectral distributions, escape, and spreading widths of the neutron final continuum states are calculated and studied by introducing a semiclassical S matrix describing the rescattering of the neutron on the target. By comparing to previous calculations done with an optical model S matrix we suggest a method to estimate the damping of single particle states in the continuum. Our calculations for the transfer cross sections and for the single particle widths are compared to available experimental data. The results of the comparison support the interpretation of the structures in the experimental spectra up to an excitation energy as high as ${\mathit{E}}_{\mathit{x}}$∼20 MeV in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and ${\mathit{E}}_{\mathit{x}}$∼30 MeV in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ as due to the population of single particle states of high spin.

A semiclassical (WKB) method within fixed energy inverse scattering theory has been used to analyze the differential cross section from the elastic scattering of 1449 MeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions off of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ and of 1503 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions off of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. Excellent, statistically significant, fits to the ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{208}{}_{}{}^{}$Pb experimental data have been found using a McIntyre form for the scattering function but with diverse sets of parameter values. There are corresponding diverse interaction potentials. To fit the ${}_{}{}^{16}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C data, a Regge pole term was needed to supplement the McIntyre form. Inversion of those scattering functions resulted in interaction potentials that vary noticeably within the sensitive radial regions. In addition, conventional optical model potentials have been obtained with which direct solution of the Schrödinger equations result in similar excellent fits to the data. It is shown that these large ambiguities in the potentials are due, in the main, to the limited angular range of the cross-section data and although the corresponding cross-section shapes beyond the measured scattering angle range for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{208}{}_{}{}^{}$Pb collision vary over many orders of magnitude, it is unlikely that experiments can be made sensitive enough to select from among them because those cross sections are so small.

The subbarrier fusion of heavy ions is discussed when one of the nuclei is excited to a resonant state. The effect of the width of the resonant state on the barrier penetration is calculated within a schematic model. It is concluded that the width could either enhance or hinder the fusion probability, depending on the relative importance of the spreading to escape parts of the width. Application of the theory to the fusion of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ with ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at near-barrier energies is made. The resulting fusion cross section calculated with coupling to the soft giant dipole state in ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ was found to be more than an order of magnitude smaller, in the barrier region, and larger, at subbarrier energies, than the uncoupled one.

We investigate the total cross section and its target dependence for ${\mathit{K}}^{+}$-nucleus scattering using a relativistic momentum-space optical potential model which incorporates relativistically normalized wave functions, invariant two-body amplitudes, covariant kinematics, and an exact full-Fermi averaging integral. The definition of the total cross section in the presence of a Coulomb interaction is reviewed and the total cross section is calculated in a way that is consistent with what is extracted from experiment. In addition, the total cross sections for a nucleus and for the deuteron are calculated utilizing the same theory. This minimizes the dependence of the ratio of these cross sections on the details of the theory. The model dependence of the first-order optical potential calculations is investigated. The theoretical results are found to be systematically below all existing data.

We have studied in detail the electromagnetic dissociation of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ projectiles at 14.6 GeV/(c nucleon), interacting with Pb, Sn, Cu, and Al targets. Exclusive cross sections were measured for several decay channels, including final states involving the emission of protons, neutrons, and α particles. Excitation energy distributions for the 1n${+}^{27}$Si and 2p${+}^{26}$Mg decay channels were reconstructed with a resolution of 2 MeV, using a constrained kinematic fit. The energy distributions obtained for 1n${+}^{27}$Si are in good agreement with the σ(γ,n) photoneutron cross sections multiplied by the virtual photon spectrum obtained in the Weizsäcker-Williams approximation. A search for the double photon excitation process, based on the dependence of the cross sections on the target atomic number, was performed.

String fusion in hA collisions at high energies is studied as a manifestation of the simultaneous interactions of a projectile with several nucleons. It is shown that such multinucleon interactions lead to effects of leading order in the nucleus atomic number A, in spite of the fact that they come from rare nuclear configurations. In this approach, string fusion also leads to a decrease of the multiplicities, which however stay proportional to A in the central region.

The main new result of this paper is the calculation of the initial and final state interaction in a hard exclusive proton-deuteron reaction. We find that for spectator momenta ≤350 MeV/c and ${\mathit{p}}_{\mathit{t}}$∼0 the effect of initial and final state interactions can be accounted for by rescaling the cross section calculated within the plane-wave impulse approximation. We show that the strong dependence of the amplitude for NN hard scattering on the collision energy and the exclusive nature of the quasielastic large-angle pd scattering can be used to magnify the effects of short-range nucleon correlations. The feasibility to investigate in this kinematical region the role of relativistic effects in the deuteron wave function is demonstrated by comparing the predictions of different relativistic approaches. It is demonstrated also that in these kinematics the final and initial state interactions reduce sensitivity of the cross section to uncertainties in the high-momentum component of the deuteron wave function. We also find that for ${\mathit{p}}_{\mathit{z}}$∼0 and 150 MeV/c≥${\mathit{p}}_{\mathit{t}}$≥50 MeV/c initial and final state interaction strongly reduce the cross section while relativistic effects are very small. This kinematic is optimal for color-transparency studies. Binding effects due to short-range correlations in the deuteron are discussed as well.

The energy densities achieved during central collisions of large nuclei at Brookhaven’s AGS may be high enough to allow the formation of quark-gluon plasma. Calculations based on relativistic nucleation theory suggest that rare events, perhaps one in every ${10}^2$ or ${10}^3$, undergo the phase transition. Experimental ramifications may include an enhancement in the ratio of pions to baryons, a reduction in the ratio of deuterons to protons, and a larger source size as seen by hadron interferometry.

The photon-gluon fusion process into a pair of heavy quarks is studied for peripheral Pb+Pb collisions at Large Hadron Collider (LHC) energies. The double differential cross section with respect to the invariant mass and the rapidity of the produced quark pair at zero rapidity is directly proportional to the gluon distribution in the nuclear medium. Differential cross sections for the b-quark production lie well in the μb/GeV regime which will allow the deduction of the gluon distribution at low x. Rapidity cuts for the actual detectors are also considered.

The multiparticle Bose correlations of bosons emitted from dispersed thermal droplets of quark-gluon plasma are simulated by a Monte Carlo process. Multiparticle Bose correlations can offer more sensitivity to probe the granularity of the boson-emitting source than two-particle Bose correlations. A promising signal of the existence of a mixed phase of quark-gluon plasma and hadronic gas can be obtained from multiparicle observables.

Absolute ${\mathrm{\pi }}^{\pm }$p elastic scattering differential cross sections have been measured at five incident pion energies between 87 and 139 MeV. An active target of scintillator material (${\mathit{CH}}_{1.1}$) was used to detect recoil protons in coincidence with scattered pions. Pions were detected at forward angles between 27 and 98${\mathrm{°}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ where the low-energy recoil protons stop in the target. The cross sections, typically 5–10% lower than phase shift predictions for ${\mathrm{\pi }}^{+}$p and 10–20% lower for the ${\mathrm{\pi }}^{\mathrm{-}}$p cross sections, are consistent with earlier measurements by this group.

Recent works concerning QCD sum rules in nuclear matter have provided a new method for the calculation of the nucleon self-energy in matter. The results of that program depend strongly on assumptions made concerning the density dependence of four-quark condensates. If a factorization scheme is used to express the four-quark condensate values in terms of the two-quark condensates, the (Lorentz) scalar self-energy of the nucleon is small. However, if the four-quark condensates have only a weak density dependence, the nucleon scalar self-energy is large and attractive, and is in accordance with Dirac phenomenology. In this paper our goal is to show how the Nambu–Jona-Lasinio model may be used to calculate the density dependence of four-quark condensates. As an elementary example we calculate some of the contributions to a four-quark condensate containing scalar-isoscalar q¯q pairs. These calculations suggest only a very small modification of the value of the scalar-isoscalar condensate in matter relative to the value obtained in the factorization scheme. However, when we continue our study of the correlator of operators with the quantum numbers of the nucleon, we encounter some new and important terms among the four-quark condensates. These have their origin in an exchange process between diquarks in the nucleon and diquarks present in the nucleons of the nuclear medium (nuclear matter). These terms may be taken to represent the effects of ‘‘diquark condensates’’ they are present in nuclear matter. If we use the interpolating field advocated by Ioffe we obtain a correction that eliminates the problematic density dependence of the four-quark condensates described above, if nuclear matter contains a similar amount of scalar (T=0) diquarks and axial-vector (T=1) diquarks. We believe that our paper provides increased confidence in the use of QCD sum rules in the study of the properties of hadrons in matter.

A microscopic model of the electromagnetic form factor of the nucleon is developed in a hadronic framework, including pions, nucleons and the Δ-resonance explicitly. The spacelike on-shell form factors are reproduced and predictions for the half off-shell dependence are made. The impact of this off-shell dependence in the time like sector (${\mathit{q}}^2$<1 ${\mathrm{GeV}}^2$, thus including the region of vector meson dominance) is of main interest in this investigation.

Two-loop corrections with scalar and vector form factors are calculated for nuclear matter in the Walecka model. The on-shell form factors are derived from vertex corrections within the framework of the model and are highly damped at large spacelike momenta. The two-loop corrections are evaluated first by using the one-loop parameters and mean fields and then by refitting the total energy/baryon to empirical nuclear matter saturation properties. The modified two-loop corrections are significantly smaller than those computed with bare vertices. Contributions from the anomalous isoscalar form factor of the nucleon are included for the first time. The effects of the implicit density dependence of the form factors, which arise from the shift in the baryon mass, are also considered. Finally, necessary extensions of these calculations are discussed.

The electromagnetic interaction with quarks is investigated through a relativistic, electromagnetic gauge-invariant treatment. Gluon dressing of the quark-photon vertex and the quark self-energy functions is described by the inhomogeneous Bethe-Salpeter equation in the ladder approximation and the Schwinger-Dyson equation in the rainbow approximation, respectively. Results for the calculation of the quark-photon vertex are presented in both the timelike and spacelike regions of photon momentum squared; however, emphasis is placed on the spacelike region relevant to electron scattering. The treatment presented here simultaneously addresses the role of dynamically generated qq¯ vector bound states and the approach to asymptotic behavior. The resulting description is therefore applicable over the entire range of momentum transfers available in electron scattering experiments. Input parameters are limited to the model gluon two-point function, which is chosen to reflect confinement and asymptotic freedom, and are largely constrained by the obtained bound-state spectrum.

We propose a unified approach to parity nonconservation in compound nuclei in which statistical and collective properties both enter the theory and play an important role. Taking the model space to consist of 0-ħω excitations and motivating our choice of the microscopic effective interaction by the doorway picture of Auerbach, the effect of the one-body parity-violating (PV) interaction enters as a renormalization of the standard two-body PV interaction through collective $0^{\mathrm{-}}$ nuclear excitations. We present semi-quantitative numerical results and compare with previous models. For the model space chosen, the sizes of the contribution from the one- and two-body PV interactions are shown to be comparable. This contrasts to the extreme statistical model (complete mixing in a large model space containing 1-ħω as well as 0-ħω excitations), where the one-body PV interaction dominates. We also find that the dynamics of the $0^{\mathrm{-}}$ resonances and their coupling to nucleons is a more important quantitative consideration than hitherto recognized.

We detect β-delayed γ rays emitted in ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ decay and use these results plus our previous work on β-delayed proton yields to calculate B(GT) values for the ${}_{}{}^{37}{}_{}{}^{}\to _{}^{37}{}_{}{}^{}$K transitions. We compare these results to the isospin-analog B(GT) values inferred from a high-resolution ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) study. Although the new β decay and (p,n) results remove some of the previously noted discrepancies between B(GT) values measured in ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ decay and those inferred from ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) cross sections, significant discrepancies remain.

Backward ω(782)-meson production in the pd${\to }^3$Heω reaction has been measured from threshold up to an ω center-of-mass momentum of 625 MeV/c. The averaged squared amplitude rises rapidly from threshold to a maximum value of about 70 nb/sr at 180 MeV/c, decreasing thereafter. This striking behavior, which is very similar to that already observed for ${\mathrm{\pi }}^{\mathrm{-}}$p→nω, may be caused by a final-state interaction between the pions from the ω decay and the recoil nucleus.

Six superdeformed bands have been observed in ${}_{}{}^{193}{}_{}{}^{}\mathrm{Pb}$ following the ${}_{}{}^{174}{}_{}{}^{}\mathrm{Yb}$${(}^{24}$Mg,5n) reaction at a beam energy of 131 MeV. The in-beam γ rays were detected with gammasphere early implementation. Two of the bands have dynamic moments of inertia which have an anomalously low increase with rotational frequency, and are interpreted as the favored and unfavored signature components of the N=7 neutron orbital. The other four bands have increasing dynamic moments of inertia typical of superdeformed bands in the A=190 region, and are interpreted as two pairs of signature partner bands based on high-K quasineutron excitations. The effects of the intruder N=7 neutron orbital on the superdeformed rotational characteristics are discussed.

The electrofission cross section of ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ was measured in the range 80–180 MeV. A pronounced inflexion, corresponding to a sharp structure in the (γ,f) curve, shows up around 140 MeV. A photofission model, based on a photopion-deuteron reabsorption process, was worked out to explain this finding. Good agreement between calculation and experimental data was achieved.