Using a standard beam attenuation technique, proton total reaction cross sections (${\mathrm{\sigma }}_{\mathit{R}}$) for ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ have been measured at seven incident energies from 23 to 48 MeV to an absolute accuracy of 1 to 3%. The results have been compared both with nonrelativistic optical model predictions using global parameters and a relativistic optical model using a standard mixture of potential terms. Nuclear trans- parency calculations have also been made for these nuclei using all published data below 100 MeV.

Double-differential cross sections for proton and deuteron production in fast neutron induced reactions on carbon are reported for three incident neutron energies: 42.5, 62.7, and 72.8 MeV. Angular distributions were measured at laboratory angles between 20° and 160°. Procedures for data taking and data reduction are presented. Energy-differential cross sections and total cross sections are also reported. Experimental cross sections are compared with existing data and with theoretical calculations in the frame of the intranuclear cascade model.

We have used γ-ray tagging to identify a secondary isomeric beam of the short-lived, high-spin isomer ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}_{}^{\mathit{m}}{}_{}{}^{}$ (${\mathit{E}}_{\mathit{x}}$=1.1 MeV, ${\mathit{J}}^{\mathrm{\pi }}$=$5^{+}$) produced at the K1200 cyclotron at the National Superconducting Cyclotron Laboratory. Elastic scattering of p${+}^{18}$${\mathrm{F}}^{\mathit{m}}$ at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≊20 MeV was observed using the characteristic γ decays of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}_{}^{\mathit{m}}{}_{}{}^{}$ (${\mathit{T}}_{1/2}$=163 ns) to identify the state of the projectile after the scattering, thus minimizing the probability of excitation of the beam and, hence, nonelastic scattering.

Angular distributions of differential cross section and vector analyzing power have been measured for the ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$${(}^6$Li→${,}^7$Li${)}^{25}$Mg reaction at 60 MeV bombarding energy. Finite-range distorted-wave Born approximation calculations were found to reproduce much of the structure of the data, although the predictions were approximately 3° out of phase with the data. Finite-range coupled-channels Born approximation calculations including inelastic excitations in ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, using coupling schemes derived from elastic scattering analyses, modified the predictions only slightly and did not remove the phase discrepancy.

The average multiplicities of intermediate mass fragments (IMFs) for central heavy-ion collisions in the (nearly) symmetric entrance channels ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$${+}^{27}$Al, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{45}$Sc, ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$${+}^{93}$Nb, and ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$${+}^{139}$La, are systematically studied over a wide range of intermediate beam energies. Cuts on experimental variables commonly assumed to be correlated with the impact parameter are used to select the most central collisions. The results for six different centrality variables are compared, and the extent to which measurements of the multiplicities of IMFs in small impact parameter collisions are affected by the variable used to select the central events is discussed. General methods for locating such ‘‘autocorrelations’’ are described. The two centrality observables that are the least autocorrelated with the number of intermediate mass fragments are identified, and these variables are used to select the most central collisions. The entrance channel mass and beam energy dependence of the experimental IMF multiplicities are presented and compared to a variety of model predictions. The models picturing the disassembly as a sequential binary process always underpredict the experimental IMF multiplicities. A generally more accurate reproduction of these multiplicities is provided by several similar chemical equilibrium models commonly assumed to be the theoretical description of multifragmentation.

In an effort to study the effect of the entrance channel mass asymmetry on the fusion process at near-barrier energies, we have measured the fusion cross section and its distribution according to the different evaporation residues for the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{142}$Ce, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{138}$Ba, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$${+}^{122}$Sn systems. All these systems lead to the same compound nucleus ${}_{}{}^{170}{}_{}{}^{}\mathrm{Hf}$. The measurements were performed using a delayed x-ray technique. For the last two systems we have also measured the fission cross sections in the same bombarding energy range. This experimental information can be used to restrict the free parameters of the statistical model used to account for the relative yield. A constrained and realistic statistical decay model is useful in reducing the uncertainties in the determination of the spin distribution from measurements of gamma multiplicities for these systems. The excitation function for the fusion cross section can be described using a schematic coupled channels calculation with realistic coupling strengths. Our results show no umambiguous effect that can be associated with the entrance channel mass asymmetry.

In this paper, we present the measured differential cross sections for the transition between the 1/$2^{\mathrm{-}}$${,}^{13}$C(g.s.) and the 1/$2^{+}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$(2.34 MeV) state, excited in the (p,n) reaction at ${\mathit{E}}_{\mathit{p}}$=160 MeV and at ${\mathit{E}}_{\mathit{p}}$=186 MeV. The ΔL=1, ΔS=1, ΔJ=$0^{\mathrm{-}}$ contribution in the 1/$2^{\mathrm{-}}$→1/$2^{+}$ transition, which provides direct information on pionlike transitions, was the main motivation of these studies.

Projectilelike residue yields and momentum distributions from the reaction of 70 MeV/nucleon ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ with ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ at 0° were studied. The data is compared with a model developed originally for higher energies (>200 MeV/nucleon), data from prior experiments performed at both higher and lower bombarding energies, and a semiempirical parametrization derived from high energy systematics.

Angular distributions of differential cross section and the analyzing powers ${\mathit{iT}}_{11}$, ${\mathit{T}}_{20}$, and ${}_{}{}^{\mathit{T}}{}_{}{}^{}$${\mathit{T}}_{20}$ have been measured for the elastic scattering of polarized ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ by ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ at an incident energy of 70.5 MeV. These data have been compared with the results of coupled-channels (CC) calculations with central interaction and coupling potentials generated using the cluster-folding (CF) method. The significance of spin-dependent potentials and the D-state admixture in the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ground state wave function are discussed.

We present the experimental results on multifractal structure of medium energy particles in 800-GeV proton-AgBr interactions. We observe a power-law dependence of the multiplicity moments on mean multiplicity in varying bin widths of the angular distribution. The experimental values of generalized dimensions are determined from the slopes for two different categories of interactions in different multiplicity regions. The observed behavior of generalized dimensions ${\mathit{D}}_{\mathit{q}}$ and of the related singularity spectrum shows a consistent departure from randomness and is a typical multifractal. The observations support a possible cascading mechanism in the emission process of target fragmented medium energy protons. The inhomogeneity of the probability distribution measured by the difference 1-${\mathit{D}}_{\mathit{q}}$ decreases with increase in the average multiparticle density.

A microscopic model for the NN¯→ππ process is presented in the meson exchange framework, which in the pseudophysical region agrees with available quasiempirical information. The scalar (σ) and vector (ρ) piece of correlated two-pion exchange in the pion-nucleon interaction is then derived via dispersion integrals over the unitarity cut. Inherent ambiguities in the method and implications for the description of pion-nucleon scattering data are discussed.

We propose a model that provides a unified description of the nuclear equation of state and fragmentations. The equation of state is evaluated in the Bragg-Williams as well as in the Bethe-Peierls approximations and compared with that in the mean field theory with Skyrme interactions. The model shows a liquid-gas type phase transition. The nuclear fragment distributions are studied for different densities at finite temperatures. Power law behavior for fragments is observed at the critical point. The study of the fragment distribution and the second moment ${\mathit{S}}_2$ shows that the thermal critical point coincides with the percolation point at the critical density. High temperature behavior of the model shows characteristics of chemical equilibrium.

We study the effects of medium modifications on the contribution of relativistic two-body meson exchange and isobar currents and real-pion production currents to the transverse response function of nuclei. In particular the consequences of rescattering of the Δ isobar, effective masses, and realistic momentum distributions are considered. It is found that the two-body isobar and real-pion production current account for most of the observed strength in the dip region. Our results do not support a large modification of the Δ-isobar mass. We compare our model with the Δ-hole model and in doing so confirm the microscopic picture of several of its phenomenological ingredients. Finally, the use of more realistic momentum distributions, obtained from relativistic mean field single-particle wave functions gives rise to results that are not much different from those obtained in the Fermi-gas model and compare fairly well with the data.

It is discussed how the introduction of a nonlocal potential in the relative coordinate of a nuclear collision described by a simple model Hamiltonian can also account for an enhancement in the nuclear fusion cross section. The interplay between this effect and the channel coupling interaction is studied in this simple model and their different contributions to the fusion cross sections are analyzed.

We examine a symmetrical form of spin-dependent sum rules, together with an improved treatment of errors, in an analysis of 0${\mathit{f}}_{7/2}$ proton transfer on ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$. A spin distribution proportional to (2J’+1), where J’ is the final state spin, emerges as a likely candidate for high-excitation energy spectroscopic strength. The consequences for sum-rule analyses are discussed.

The optical model potentials for nucleon-nucleus elastic scattering at 65 meV are calculated for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ in first-order multiple scattering theory, following the prescription of the spectator expansion, where the only inputs are the free nucleon-nucleon (NN) potentials, the nuclear densities, and the nuclear mean field as derived from microscopic nuclear structure calculations. These potentials are used to predict differential cross sections, analyzing powers, and spin rotation functions for neutron and proton scattering at 65 MeV projectile energy and compared with available experimental data. The theoretical curves are in very good agreement with the data. The modification of the propagator due to the coupling of the struck nucleon to the residual nucleus is seen to be significant at this energy and invariably improves the congruence of theoretical prediction and measurement.

We use the Boltzmann-Uehling-Uhlenbeck model with a momentum-dependent nuclear mean field to simulate the dynamical evolution of heavy ion collisions. We reexamine the azimuthal anisotropy observable, proposed as sensitive to the equation of state of nuclear matter. We obtain that this sensitivity is maximal when the azimuthal anisotropy is calculated for nuclear composite fragments, in agreement with some previous calculations. As a test case we concentrate on semicentral ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$${+}^{197}$Au collisions at 400A MeV.

We present results on rapidity and transverse momentum distributions of inclusive charm quark production in hadronic and heavy-ion collisions at RHIC and LHC energies, including the next-to-leading order O(${\mathrm{\alpha }}_{\mathit{s}}^3$), radiative corrections, and the nuclear shadowing effect. We determine the hadronic and the effective (in-medium) K factor for the differential and total inclusive charm cross sections. We find the fraction of central and inelastic events that contain at least one charm quark pair at LHC energies and obtain the effective A dependence of the inclusive charm production in proton-nucleus and nucleus-nucleus collisions at RHIC and in nucleus-nucleus collisions at the LHC. We discuss theoretical uncertainties inherent in our calculation. In particular, we show how different extrapolations of gluon density in a nucleon and in a nucleus to the low-x region introduce large theoretical uncertainty in the calculation of charm production at LHC energies.

We consider the production of strange particles in relativistic nucleus-nucleus collisions. We employ a quark-gluon plasma (QGP) formalism, incorporating the production of the (anti)quarks in the plasma during equilibration by the gluon field. We assume generally accepted T(${\mathrm{\mu }}_{\mathit{q}}$=0) and ${\mathrm{\mu }}_{\mathit{q}}$(T=0) values to construct a phase curve, defining an approximate lower limit of the ideal QGP phase. We express the strange particle ratios as function of ${\mathrm{\mu }}_{\mathit{q}}$ and T along this curve and predict quantitatively their minimum QGP values. We analyze the NA36 and WA85 CERN experiments and obtain the quarkchemical potentials, ${\mathrm{\mu }}_{\mathit{q}}$, ${\mathrm{\mu }}_{\mathit{s}}$ and the chemical equilibration, ${\gamma }_{\mathit{s}}$. The gluon sector, providing the q¯’s, is necessary for the correct and consistent estimation of these quantities and prediction of all strange particle ratios. We put forward that the values of T, ${\mathrm{\mu }}_{\mathit{q}}$, ${\mathrm{\mu }}_{\mathit{s}}$, and ${\gamma }_{\mathit{s}}$ are the only significant quantities determining a possible phase transition, not the magnitude of any strange particle ratio, as previously proclaimed. We find that the 200 GeV/nucleon ${}_{}{}^{32}{}_{}{}^{}\mathrm{induced}$ interactions at midrapidity may have approached the ideal QGP phase to within about 60%.

To determine the impact parameter of heavy-ion collisions from the observables is of crucial importance for comparing the experimental results with theory. For central collisions all methods which rely on a single observable have failed. We propose to determine the impact parameter by a neural network. We find that a combination of three observables allows the determining of the impact parameter four times more accurate than a single observable. We investigate in detail which combination of observables provides the best results.