Cross-section measurements on the production of ${}^{94}{\mathrm{Tc}}^m$ in the reactions ${}^{93}\mathrm{Nb}{(}^3\mathrm{He},2n),$ ${}^{92}\mathrm{Mo}(\alpha ,x),$ and ${}^{94}\mathrm{Mo}\mathrm{}(p,n)\mathrm{}$ were performed recently at Jülich in order to investigate ways of producing this radioisotope on a large scale for nuclear medical application. Those experiments also yielded the excitation functions for the reactions ${}^{93}\mathrm{Nb}{(}^3\mathrm{He}{,xn)}^{95,94,93}{\mathrm{Tc}}^{m,g}$ $\mathrm{}(x=1,2,3\mathrm{}),$ ${}^{93}\mathrm{Nb}{(}^3\mathrm{He}{,x)}^{93}{\mathrm{Mo}}^m,$ ${}^{93}\mathrm{Nb}{(}^3\mathrm{He}{,x)}^{92}{\mathrm{Nb}}^m$ and ${}^{93}\mathrm{Nb}{(}^3\mathrm{He}{,x)}^{89}{\mathrm{Zr}}^{m+g},$ ${}^{92}\mathrm{Mo}(\alpha {,xn)}^{95,94}\mathrm{Ru}$ $\mathrm{}(x=1,2\mathrm{}),$ ${}^{92}\mathrm{Mo}(\alpha {,x)}^{94}{\mathrm{Tc}}^{m,g}$, and ${}^{92}\mathrm{Mo}(\alpha {,p)}^{95}{\mathrm{Tc}}^g$ as well as ${}^{94}\mathrm{Mo}{\mathrm{}(p,xn)\mathrm{}}^{94,93}{\mathrm{Tc}}^{m,g}$ $\mathrm{}(x=1,2\mathrm{}).$ A theoretical study, employing the Hauser-Feshbach and the exciton-model formalism, was now undertaken to describe the cross sections of all those reactions. The data base was supplemented by cross sections retrieved from the literature, including the reactions ${}^{93}\mathrm{Nb}{(}^3\mathrm{He}{,4n)}^{92}\mathrm{Tc},$ ${}^{92}\mathrm{Mo}(\alpha {,p)}^{95}{\mathrm{Tc}}^m,$ ${}^{92}\mathrm{Mo}(\alpha {,x)}^{93}{\mathrm{Tc}}^{m,g},$ and ${}^{95}\mathrm{Mo}{\mathrm{}(p,n)\mathrm{}}^{95}{\mathrm{Tc}}^{m,g}.$ As the reactions investigated have many of the product nuclei in common, they permit the study of cross sections, in particular for the formation of pairs of isomeric states, as functions of projectile type and energy, with the cross sections for formation of nuclei via competing reactions posing additional constraints on the model parameters. Considering the rather large scatter among the experimental data sets, as well as the fact that attempts were made to describe simultaneously 25 excitation functions and 8 isomeric cross-section ratios $[{\sigma }^m/({\sigma }^m+{\sigma }^g\left)\right]$ with one consistent set of model parameters, the degree of agreement achieved between experimental and calculated quantities is remarkable. In ${}^3\mathrm{He}$-induced reactions, the adoption of a spin distribution of the level population in preequilibrium emission different from that at the equilibrium stage yielded some improvement in the description of the isomeric ratios for ${}^{95,94,93}\mathrm{Tc}$ production.

A relatively simple formalism for calculating the average neutron elastic angular distribution $\overline{d{\sigma }_{\mathrm{el}}}/d\Omega$ in the resonance region below several hundred keV is presented. The expression for $\overline{d{\sigma }_{\mathrm{el}}}/d\Omega$ depends mainly on the $R$-matrix parameters $S_0,$ $R^{\prime },$ $S_1,$ and $R_1^{\infty }.$ Comparisons between calculated and experimental angular distributions are presented for ${}^{103}\mathrm{Rh},$ ${}^{139}\mathrm{La},$ ${}^{232}\mathrm{Th},$ and ${}^{238}\mathrm{U}.$ A fit to ${}^{238}\mathrm{U}$ data at 75 keV led to a value of the $p$-wave strength function of $S_1=1.81\mathrm{}\pm 0.35\times {10}^{-4}.$ Except for measuring a complete set of individual $l=1\mathrm{}$ resonances, determining the $p$-wave strength function by fitting low-energy angular distributions is probably more reliable than, or competitive with, other techniques which are available. An analysis of elastic angular distributions as a function of neutron energy is also well suited to a search for intermediate structure in the $s$- or $p$-wave strength function.

We examine the sensitivity of the distorted-wave impulse approximation for single-nucleon electromagnetic knockout from valence orbitals to ambiguities in the one-body current operator. Violations of current conservation are classified as gauge ambiguities, whereas the elements of a particular class of structural differences off shell are labeled Gordon ambiguities. Gauge ambiguities in differential cross sections and longitudinal response functions are found to increase with missing momentum and to become particularly severe for low-$Q^2$ kinematical conditions that are far from quasifree but are sometimes used to investigate correlations. The azimuthal asymmetry may provide a useful experimental means for selecting a gauge. Gordon ambiguities increase with $Q^2$ and are larger for relativistic than for nonrelativistic approaches. Because ambiguities in the one-body current are at least as large as effects due to correlations and there are additional uncertainties due to two-body currents, final-state interactions, and relativistic distortion, we conclude that is unlikely that information about correlations can be extracted from single-nucleon knockout from valence orbitals at large missing momentum. On the other hand, gauge and Gordon ambiguities and uncertainties in final-state interactions have very little effect upon the helicity-dependent recoil polarization, which can be used to investigate the roles of two-body currents and/or possible medium modifications of the one-body current.

Results of recoil-corrected continuum shell model calculations are presented for ${}^4\mathrm{He}(\pi ,{\pi }^{\prime }{p)}^3\mathrm{H}.$ The extremely large values of $\sigma ({\pi }^{+},{\pi }^{+\prime }p)/\sigma ({\pi }^{-},{\pi }^{-\prime }p)$ are shown to be a result of neutron excitations which couple to outgoing proton channels. The large ratio will occur in regions where neutron excitations increase rapidly in a particular channel and, therefore, may be a signal for giant resonances.

Recent extensive measurements of total reaction cross sections $\left({\sigma }_R\right)$ for 38, 65, and 97 MeV deuterons on targets from ${}^9\mathrm{Be}$ to ${}^{208}\mathrm{Pb}$ were fitted with microscopic model calculations. Using accepted two- and three-parameter Fermi matter distributions for the targets, zero-range nucleon-nucleon forces, and eikonal orbits for the projectile, reasonable fits were obtained when the impact parameter was corrected for Coulomb force effects. Correcting the orbit for nuclear force effects worsened the fits somewhat, as did the use of finite-range nuclear forces; we argue however that it is redundant to make both of these corrections. The results were nearly independent of whether a Hulthén, Gartenhaus, or Gaussian form factor was used for the deuteron matter distribution. An attempt to fit older $d+\mathrm{Pb}$ ${\sigma }_R$ measurements near 25 MeV indicated either a failure of the model at low energies or a need for remeasurement of those data.

Angular distributions of a ${}^{208}$Pb beam on ${}^{208}$Pb thin targets at very small angles were measured. The shape of the experimental distribution is not Gaussian, indicating a plural scattering regime rather than multiple scattering. The distribution was well reproduced by a Monte Carlo simulation of the straggling process. For the first time we observed and quantified the influence of the production of electrons during the scattering. This effect was observed in the angular correlation of the scattered ${}^{208}$Pb nuclei detected in kinematic coincidence and also in the limiting angle of the ${}^{208}$Pb scattered in a ${}^{107,109}$Ag target. This effect introduces a spread in the scattered angle which is of the same order of magnitude as the angular straggling.

We investigate charm production in an equilibrated quark-gluon plasma produced in heavy-ion collisions at RHIC and LHC. Effective quark and gluon masses are introduced from thermal QCD calculations. Assuming a Bjorken-type longitudinal expansion and including the influence of temperature-dependent masses on the expansion, we determine the total number of $c\overline{c}$ pairs produced in the quark-gluon plasma phase. We calculate the charm production rate at leading order with massive gluons and quarks and compare our result to charm production by massless partons. We consider two different scenarios for the initial conditions, a parton gas with a rather long kinetic equilibration time and a minijet gas with a short equilibration time. In a parton gas, assuming $m_c=1.2\mathrm{}$ GeV, we obtain a substantial enhancement over the thermal charm rate from massless quarks and gluons, up to 4.9 secondary charm quark pairs in Au+Au collisions at RHIC and 245 charm pairs in Pb+Pb collisions at the LHC.

We examine Pb+Pb collisions at CERN SPS energy $158A$ GeV by employing the earlier developed and recently refined parton-cascade/cluster-hadronization model and its Monte Carlo implementation. This space-time model involves the dynamical interplay of perturbative QCD parton production and evolution, with nonperturbative parton-cluster formation and hadron production through cluster decays. Using computer simulations, we are able to follow the entwined time evolution of parton and hadron degrees of freedom in both position and momentum space, from the instant of nuclear overlap to the final yield of particles. We present and discuss results for the multiplicity distributions, which agree well with the measured data from the CERN SPS, including those for $K$ mesons. The transverse momentum distributions of the produced hadrons are also found to be in good agreement with the preliminary data measured by the NA49 and WA98 Collaborations for the collision of lead nuclei at the CERN SPS. The analysis of the time evolution of transverse energy deposited in the collision zone and the energy density suggests the existence of partonic matter for a time of more than 5 fm.

The effect of gluon shadowing on charm quark production in large impact parameter ultrarelativistic heavy ion collisions is investigated. Charm quark production cross sections are calculated for a range of noncentral impact parameters which can be determined from the global transverse energy distribution. We show that charm quark production is a good probe of the local parton density which determines the effectiveness of shadowing. We discuss why shadowing may have a spatial dependence and show that this spatial dependence may be detected in noncentral heavy ion collisions.

Bose-Einstein correlations are considered in the presence of $M$ independent chaotic sources and a coherent source. Our approach is an extension of the formulation in the quantum optics given by Glauber and Lachs. The generating functional (GF) of Bose-Einstein correlation (BEC) functions is derived, and higher order BEC functions are obtained from the GF. A diagrammatic representation for cumulants is made. The number $M$ is explicitly contained in our formulation, which is different from that given by Cramer et al. The possibility of estimating the number $M$ from the analysis of BEC functions and cumulants is pointed out. Moreover, source size dependence of multiplicity distributions is shown in a simplified case.

Relativistic heavy ion collisions are studied assuming that particles can be described by a hadron gas in thermal and chemical equilibrium. The exact conservation of baryon number, strangeness, and charge is explicitly taken into account. For heavy ions the effect arising from the neutron surplus becomes important and leads to a substantial increase in, e.g., the ${\pi }^{-}/{\pi }^{+}$ ratio. A method is developed which is suited to the study of small systems up to baryon number 20, which, unfortunately excludes cases like S-S.

The deuteron disintegration at high energies and large angles in the $d(p,2p)n$ reaction is calculated in kinematic conditions where the dominant contributions are due to soft rescatterings of the initial and final nucleons, which accompany the hard $\mathrm{pp}$ reaction. The eikonal approximation, which accounts for relativistic kinematics as dictated by Feynman diagrams, reveals the important role played by the initial and final state interactions in the angular and momentum dependences of the differential cross section. Based on these results, we propose a new and effective test, at moderate energies, of the physics relevant for the color transparency phenomenon in hadron-initiated exclusive hard processes.

We investigate in-medium corrections to the branching ratio in $K^{-}$ absorption at rest and their effect on the charged pion ${\pi }^{\pm }$ spectrum. The in-medium corrections are due to Pauli blocking, which arises if the Λ(1405) is assumed to be a $\overline{K}$-nucleon bound state and leads to a density- and momentum-dependent mass shift of the Λ(1405). Requiring that the optical potential and the branching ratio are derived from the same elementary $T$ matrix, we find that the in-medium–corrected, density-dependent $T$ matrix gives a better description of the $K^{-}$ absorption reaction than the free, density-independent one. This result suggests that the dominant component of the Λ(1405) wave function is the $\overline{K}N$ bound state.

Experimental evidence from coherent diffractive proton scattering has been reported for two narrow baryonic resonances that decay predominantly to strange particles. These states, with masses close to 2.0 GeV, would, if confirmed, be candidates for hidden-strangeness states with unusual internal structure. In this paper we examine the literature on strangeness photoproduction to seek additional evidence for or against these states. We find that one state is not confirmed, while for the other state there is some mild supporting evidence favoring its existence. New experiments are called for, and the expected photoproduction line shapes are calculated.

We study the short-range nucleon-nucleon interaction in a chiral constituent quark model by diagonalizing a Hamiltonian comprising a linear confinement and a Goldstone boson exchange interaction between quarks. The six-quark harmonic oscillator basis contains up to two excitation quanta. We show that the highly dominant configuration is $|s^4{p}^2\left[42{]}_O\right[51{]}_{\mathrm{FS}}〉$ due to its specific flavor-spin symmetry. Using the Born-Oppenheimer approximation we find a strong effective repulsion at zero separation between nucleons in both ${}^3{S}_1$ and ${}^1{S}_0$ channels. The symmetry structure of the highly dominant configuration implies the existence of a node in the $S$-wave relative motion wave function at short distances. The amplitude of the oscillation of the wave function at short range will be, however, strongly suppressed. We discuss the mechanism leading to the effective short-range repulsion within the chiral constituent quark model as compared to that related with the one-gluon exchange interaction.

A relativistic light front treatment of nuclei is developed by performing light front quantization for a chiral Lagrangian. The energy momentum tensor and the appropriate Hamiltonian are obtained. Three illustrations of the formalism are made. (i) Pion-nucleon scattering at tree level is shown to reproduce soft pion theorems. (ii) The one boson exchange treatment of nucleon-nucleon scattering is developed and shown (by comparison with previous results of the equal time formulation) to lead to a reasonable description of nucleon-nucleon phase shifts. (iii) The mean-field approximation is applied to infinite nuclear matter and the plus momentum distributions of that system are studied. The mesons are found to carry a significant fraction of the plus momentum, but are inaccessible to experiments.

Charged current scattering of ${\nu }_{\mu }$ on ${}^{12}\mathrm{C}$ has been studied using a ${\pi }^{+}$ decay-in-flight ${\nu }_{\mu }$ beam at the Los Alamos Meson Physics Facility. A sample of 56.8 $\pm 9.6$ events satisfying criteria for the exclusive reaction ${}^{12}{\mathrm{C}(\mathrm{\nu }}_{\mathrm{\mu }}{,\mathrm{\mu }}^{\mathrm{-}}{)}^{12}{\mathrm{N}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section $(6.6\mathrm{}\pm 1.0\pm 1.0)\times {10}^{-41}{\mathrm{cm}}^2$ agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible ${}^{12}\mathrm{N}$ states ${}^{12}\mathrm{C}({\nu }_{\mu },{\mu }^{-})X.\mathrm{}$ This flux-averaged cross section is $(11.2\mathrm{}\pm 0.3\pm 1.8)\times {10}^{-40}{\mathrm{cm}}^2,$ which is approximately half of that given by a recent continuum random-phase approximation calculation.

The existence of a nuclear electric octupole moment (EOM) requires both parity and time invariance violation. The EOM’s of odd $Z$ nuclei that are induced by a particular $T$- and $P$-odd interaction are calculated. We compare such octupole moments with the collective EOM’s that can occur in nuclei having a static octupole deformation. A nuclear EOM can induce a parity- and time-invariance-violating atomic electric dipole moment, and the magnitude of this effect is calculated. The contribution of a nuclear EOM to such a dipole moment is found, in most cases, to be smaller than that of other mechanisms of atomic electric dipole moment production.

The incoherent matrix elements of the exotic $\left({\mu }^{-}{,e}^{-}\right)$ conversion in nuclei process are studied in detail for a set of nuclei throughout the periodic table in the context of the quasiparticle random phase approximation (RPA). The contaminations, usually inserted in the $1^{-}$ RPA excitation modes (the most important incoherent $\mu \to e$ conversion channel), are removed by explicitly constructing the purely spurious center-of-mass state. We found that mostly the lowest-lying $1_1^{-}$ state is affected by the use of non-self-consistent single-particle energies and a truncated model space in the RPA. To a good approximation we can regard this state as fully spurious and treat the other states as the physical ones. The elimination of the spuriousness requires a different renormalization of the interaction. This allows us to reproduce the excitation spectrum, needed to calculate reliably the incoherent matrix elements of the $\mu \to e$ process, with realistic forces (Bonn potential) which cannot be achieved with the contaminated wave functions. We focus on the investigation of the incoherent rate of ${}^{48}\mathrm{Ti},$ from which the best upper limit for the flavor number violation has been extracted, and ${}^{208}\mathrm{Pb},$ which is currently used in the SINDRUM II experiment at PSI.

We calculate accurately the number of solar neutrino events expected as a function of solar zenith angle, with and without neutrino oscillations, for detectors at the locations of Super-Kamiokande, SNO, and the Gran Sasso National Laboratory. Using different Earth models to estimate geophysical uncertainties, and different solar models to estimate solar uncertainties, we evaluate distortions predicted by the Mikheyev-Smirnov-Wolfenstein (MSW) effect in the zenith angle distributions of solar neutrino events. The distortions are caused by oscillations and by $\nu$-$e$ interactions in the Earth that regenerate ${\nu }_e$ from ${\nu }_{\mu }$ or ${\nu }_{\tau }.$ We show that the first two moments of the zenith-angle distribution are more sensitive to the small mixing angle MSW solution than the conventionally studied day-night asymmetry. We present iso-$\sigma$ contours that illustrate the potential of Super-Kamiokande, SNO, BOREXINO, ICARUS, and HERON/HELLAZ for detecting the Earth regeneration effect at their actual locations (and at the equator). MSW solutions favored by the four pioneering solar neutrino experiments predict characteristic distortions for Super-Kamiokande, SNO, BOREXINO, and ICARUS that range from being unmeasurably small to $>5\mathrm{}\sigma$ (stat) after only a few years of observations.