A precision measurement of absolute ${\pi }^{\pm }p$ elastic differential cross sections at incident pion laboratory kinetic energies from $T_{\pi }=141.15\mathrm{}$ to 267.3 MeV is described. Data were obtained detecting the scattered pion and recoil proton in coincidence at 12 laboratory pion angles from $55°$ to $155°$ for ${\pi }^{+}p$ and six angles from $60°$ to $155°$ for ${\pi }^{-}p.\mathrm{}$ Single arm measurements were also obtained for ${\pi }^{+}p$ energies up to 218.1 MeV, with the scattered ${\pi }^{+}$ detected at six angles from $20°$ to $70°.$ A flat-walled, supercooled liquid hydrogen target and solid ${\mathrm{CH}}_2$ targets were used. The data are characterized by small uncertainties, $\sim 1–2\%$ statistical and $\sim 1–1.5\%$ normalization. The reliability of the cross section results was ensured by carrying out the measurements under a variety of experimental conditions to identify and quantify the sources of instrumental uncertainty. Our lowest- and highest-energy data are consistent with overlapping results from TRIUMF and LAMPF. In general, the Virginia Polytechnic Institute SM95 partial-wave analysis (PWA) solution describes our data well, but the older Karlsruhe-Helsinki PWA solution KH80 does not.

From an analysis of various types of data obtained in relativistic nuclear collisions, the following picture has emerged in thermal and hydrodynamical descriptions: as the fluid expands and cools, particles first undergo a chemical freeze out at $T_{\mathrm{ch}.f.\mathrm{}}\sim 160–200$ MeV, then a thermal freeze out at $T_{\mathrm{th}.f.\mathrm{}}\sim 100–140$ MeV. In this paper we show how to incorporate these separate freeze outs consistently in a hydrodynamical code via a modified equation of state (general case) or via a modified Cooper-Frye formula (particular case of $T_{\mathrm{ch}.f.\mathrm{}}$ close to $T_{\mathrm{th}.f.\mathrm{}}$ or few particle species undergoing early chemical freeze out). The modified equation of state causes faster cooling and may have sizable impact on the predicted values of observables.

We propose a method for calculating the reaction rates and transition amplitudes of generic processes taking place in a many-body system in equilibrium at temperature T. The relationship of the scattering and decay amplitudes as calculated in thermofield dynamics (TFD) to the conventional techniques is established. It is shown that in many cases the calculations are relatively easy in TFD.

Inclusive and semi-inclusive measurements are presented for antiproton $\left(\overline{p}\right)$ production in proton-nucleus collisions at the Alternating Gradient Synchrotron (AGS). The inclusive yields per event increase strongly with increasing beam energy and decrease slightly with increasing target mass. The $\overline{p}$ yield in 17.5 $\mathrm{GeV}/c$ $p+\mathrm{Au}$ collisions decreases with grey track multiplicity, $N_g,$ for $N_g>0,$ consistent with annihilation within the target nucleus. The relationship between $N_g$ and the number of scatterings of the proton in the nucleus is used to estimate the $\overline{p}$ annihilation cross section in the nuclear medium. The resulting cross section is at least a factor of 5 smaller than the free $\overline{p}-p$ annihilation cross section when assuming a small or negligible formation time. Only with a long formation time can the data be described with the free $\overline{p}-p$ annihilation cross section.

We explore skewed parton distributions for simple, model wave functions in a truncated two-body Fock space. Consideration of non-Gaussian wave functions is our main emphasis, from which we observe the distributions are bimodal (there can be two distinct peaks) in the Fock-space diagonal overlap region $(x>\mathrm{}\xi ).\mathrm{}$ We demonstrate that this behavior arises from convoluting two light-front wave functions to form the skewed parton distribution. Furthermore, the factorization Ansätze, which have been used often, are shown not to hold. At high |t|, we can write the skewed parton distribution in terms of quark distribution amplitudes and perturbative wave functions thereby providing new tests.

The energy spectra of the antimony isotope ${}^{109}\mathrm{Sb}$ in the $\mathrm{sdgh}$ shell are calculated in the nuclear shell model approach by using the CD-Bonn nucleon-nucleon interaction. The modified Drexel University parallel shell model code (DUPSM) was used for the calculations with maximum Hamiltonian dimension of 762 253 of 5.14% sparsity. The energy levels are compared to the recent experimental results. The calculations were done on the Cyborg Parallel Cluster System at Drexel University.

We point out a distinguishing difference between constituent quark models based on one-gluon exchange and one-boson exchange dynamics. In the latter, the $P_{11}$ nucleon resonance with predominantly symmetrical spatial wave function in the $N=4\mathrm{}$ band becomes strongly attracted such that it drops below some states in the $N=2\mathrm{}$ band. Calculations of strong decay widths are presented in order to establish an identification with experimental states. Our results are relevant for the interpretation of the fourth $P_{11}$ resonance that was found in the partial wave analysis of the Zagreb group and recently discussed by Capstick et al. in the framework of a model based on one-gluon exchange.

The sequence of states built on the second ${\frac{7}{2}}^{+}$ state in ${}^{121,123,125}\mathrm{I}$ are interpreted to be associated with the low-$K$ prolate $\pi g_{7/2}\left[420\right]\frac{1}{2}$ Nilsson orbital with admixtures from the nearby $\pi d_{5/2}\left[422\right]\frac{3}{2}$ and $\pi d_{5/2}\left[431\right]\frac{1}{2}$ orbitals on the basis of the particle-rotor model calculations. With the ground-state bands in these nuclei being already explained as arising from the oblate high-$K$ $g_{7/2}$ and $d_{5/2}$ proton configurations, the present work indicates the coexistence of oblate and prolate deformed bands based on the same proton configuration in ${}^{121,123,125}\mathrm{I}.$

The $\gamma$-ray decay schemes of ${}^{69}\mathrm{Se}$ and ${}^{67}\mathrm{As}$ have been considerably extended using the ${}^{40}\mathrm{Ca}{(}^{32}\mathrm{S}{,2pn)}^{69}\mathrm{Se}$ and ${}^{40}\mathrm{Ca}{(}^{32}\mathrm{S},\alpha {p)}^{67}\mathrm{As}$ reactions at 100 MeV and ${}^{40}\mathrm{Ca}{(}^{36}\mathrm{Ar},\alpha {2pn)}^{69}\mathrm{Se}$ and ${}^{40}\mathrm{Ca}{(}^{36}\mathrm{Ar},2\mathrm{}\alpha {p)}^{67}\mathrm{As}$ reactions at 145 MeV, with the aim of studying oblate bands arising from the strong coupling of a valence $g_{9/2}$ particle (or hole) to the oblate deformed ground state band of ${}^{68}\mathrm{Se}.$ A new $T_{1/2}=12\mathrm{}\pm 2\hspace{0.5em}\mathrm{ns}\hspace{0.5em}{J}^{\pi }{=9/2\mathrm{}}^{+}$ isomeric bandhead was identified in ${}^{67}\mathrm{As}.$ A transitional quadrupole moment of $Q_0=-2.7\left(6\right)\mathrm{}\hspace{0.5em}e\mathrm{b}$ was deduced for the band built on the ${9/2}^{+}$ isomer in ${}^{69}\mathrm{Se},$ corresponding to a rigid oblate deformation of ${\beta }_2=-0.4\left(1\right),$ consistent with theoretical predictions. However, it appears that the relevant oblate configurations in ${}^{69}\mathrm{Se}$ and ${}^{67}\mathrm{As}$ are not nearly so favored as they are in ${}^{68}\mathrm{Se},$ and are rapidly crossed by prolate configurations that form the high spin yrast lines.

The second-forbidden electron-capture (EC) transition ${}^{123}\mathrm{Te}{(1/2\mathrm{}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}{)}^{123}\mathrm{Sb}{(7/2\mathrm{}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+})$ is analyzed in the framework of the proton-neutron quasiparticle random-phase approximation (pn-QRPA) and by using the quasiparticle-phonon coupling scheme. The quality of the model used to construct the phonon wave functions is supported by the analysis of the calculated $\mathrm{ft}$ values for $\beta$-decay transitions feeding states in ${}^{122}\mathrm{Te}.$ The initial state $J_i^{\pi }{=1/2\mathrm{}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}$ is represented as a pure one-quasineutron state in the ${2s}_{1/2}$ orbital and the final state $J_f^{\pi }{=7/2\mathrm{}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}$ is constructed by diagonalizing the quasiparticle-phonon coupling Hamiltonian in a basis consisting of a quasiproton state and quasineutron states coupled to pn-QRPA phonons. The influence of high-lying single-particle orbitals, in contributing to the nuclear transition matrix element, is discussed. The obtained theoretical result for the considered second-forbidden EC transition is in good agreement with the data.

Unpolarized cross sections and vector target analyzing powers for the ${}^7\mathrm{Li}\to ({\pi }^{+},{\pi }^{{+}^{\prime }}p)$ proton knockout reaction were measured using a vector polarized ${}^7\mathrm{LiH}$ target and a 240 MeV ${\pi }^{+}$ beam at the $\pi M1\mathrm{}$ channel of PSI. Typical target polarizations were >30% for ${}^7\mathrm{Li}.$ Coincident ${\pi }^{+}-p$ data are presented for three emitted pion angles (60°, 85°, and 108°). For each ${\pi }^{+}$ angle coincident data with adequate statistics were obtained for three proton angles near the quasifree ${\pi }^{+}-p$ angle. The ${\pi }^{+}$ angles were chosen to emphasize and isolate contributions to the target analyzing powers from the two-body π-nucleon interaction with a polarized nucleon whose polarization resulted from either the target polarization or from the distortion-induced effective polarization. The data are compared with factorized-amplitude distorted-wave impulse approximation (DWIA) calculations. The unpolarized cross sections are rather well described by these calculations. However, for all three angles the target analyzing powers are substantially reduced from predictions of conventional DWIA calculations. This result suggests a rather strong spin dependence in the Δ-nucleus spreading potential.

The ${}^2\mathrm{H}{(e,e}^{\prime }{\pi }^{+})$ reaction in parallel kinematics has been investigated using a dynamical model of pion electroproduction on the nucleon. A unitary $\pi \mathrm{NN}$ model has been used in order to examine the effects due to the final two-nucleon interactions, pion rescattering from the second nucleon, and intermediate $\mathrm{NN}$ and $N\Delta$ interactions. It has been found that these $\pi \mathrm{NN}$ mechanisms are small, but they can have significant contributions to the ${}^2\mathrm{H}{(e,e}^{\prime }{\pi }^{+})$ cross sections through their interference with the dominant impulse term. For the longitudinal cross sections, the effects due to the interference between the pion pole term and other production mechanisms are also found to be very large. Our findings clearly indicate that these interference effects must be accounted for in any attempt to determine from the ${}^2\mathrm{H}{(e,e}^{\prime }{\pi }^{+})$ data whether the pion form factor and/or $\pi \mathrm{NN}$ vertex of the pion pole term are modified in the nuclear medium.

We apply the perturbative chiral quark model (PCQM) at one loop to analyze the electromagnetic structure of nucleons. This model is based on an effective Lagrangian, where baryons are described by relativistic valence quarks and a perturbative cloud of Goldstone bosons. Including the electromagnetic interaction we first develop the formalism up to one loop in the Goldstone boson fluctuation relying on renormalization by use of counterterms. Local gauge invariance is satisfied both on the Lagrangian level and also for the relevant baryon matrix elements in the Breit frame. We apply the formalism to obtain analytical expressions for the nucleon charge and magnetic form factors, which are expressed in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). A detailed numerical analysis of the nucleon magnetic moments, charge and magnetic radii, and also the momentum dependence of form factors is presented.

We have made high-resolution measurements of the neutron capture and total cross sections for ${}^{116}\mathrm{Sn}$ and the neutron capture cross section for ${}^{120}\mathrm{Sn}$ from 50 eV to 500 keV at the Oak Ridge Electron Linear Accelerator (ORELA). There have been no previously reported high-resolution measurements of these cross sections in this energy range. We performed an $\mathcal{R}$-matrix analysis of our new data as well as previous total cross section data for ${}^{120}\mathrm{Sn}$ to extract parameters for 216 resonances in ${}^{117}\mathrm{Sn}$ between 100 eV and 30 keV, and 187 resonances in ${}^{121}\mathrm{Sn}$ between 350 eV and 55 keV. These resonance parameters were used to calculate the average radiation widths, average level spacings, and strength functions for s- and p-wave neutron resonances. The ${}^{116,120}\mathrm{Sn}(n,\gamma )$ astrophysical reaction rates were determined, to approximately 3% accuracy across the entire range of temperatures needed by the latest stellar models of the s process, from these resonance parameters together with our neutron capture measurements in the unresolved region. At the canonical s-process temperature of $kT=30\mathrm{}\hspace{0.5em}\mathrm{keV},$ our ${}^{116}\mathrm{Sn}(n,\gamma )$ rate agrees to within the experimental uncertainties with the most recent high-precision measurement, and our ${}^{120}\mathrm{Sn}(n,\gamma )$ rate resolves the discrepancy between two recent high-precision measurements. However, our measurements show that the most recently recommended reaction rates (which are based on extrapolations from previous measurements at higher energies) at $kT=6\mathrm{}–8\hspace{0.5em}\mathrm{keV},$ where most of the neutron exposure occurs in stellar s-process models, are too high by approximately 10–20 %. We discuss the astrophysical impact of our new rates.

We have calculated energies and widths of the three lowest $T=\frac{3}{2}$ states in ${}^{11}\mathrm{B},$ ${}^{11}\mathrm{C},$ and ${}^{11}\mathrm{N}.$ Comparison with data on known levels suggests that the ${\frac{1}{2}}^{+},T=\frac{3}{2}$ states in ${}^{11}\mathrm{B}$ and ${}^{11}\mathrm{C}$ have been misidentified. Our calculations for ${}^{11}\mathrm{N}$ are in agreement with measurements.

Giant resonances in ${}^{16}\mathrm{O}$ have been studied with inelastic scattering of 240 MeV α particles at small angles. Isoscalar $E0,$ $E1,$ and $E2\mathrm{}$ strength corresponding to $48\pm 10\%,$ $32\pm 7\%,$ and $53\pm 10\%,$ of the respective energy-weighted sum rule was identified between $E_x=11\mathrm{}–40\mathrm{MeV}$ with centroids of $21.13\pm 0.49,$ $21.67\pm 0.61,$ and $19.76\pm 0.22\mathrm{MeV}$ and root-mean-square widths of $8.76\pm 1.82,$ $7.10\pm 0.52,$ and $5.11\pm 0.17\mathrm{MeV},$ respectively. Elastic scattering and inelastic scattering to states at 6.13, 6.92, and 11.52 MeV were measured from ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=2.5\mathrm{}°$ to 11.5°.

We measured the average electronic charge $〈q〉$ of heavy ions with atomic numbers $Z=89\mathrm{}$ through 116 traversing dilute hydrogen gas with velocities ranging from 1 to 2.6 times the Bohr velocity. We observe a strong linear dependence of the average charge on the velocity of the ions, and only a weak dependence on their atomic number Z. A more detailed examination of the experimental results shows that the $〈q〉$ values reflect the influence of the $5f$ electron shell on the properties of these elements.

The role of anharmonic effects on the excitation of the double giant dipole resonance is investigated in a simple macroscopic model. Perturbation theory is used to find energies and wave functions of the anharmonic oscillator. The cross sections for the electromagnetic excitation of the one- and two-phonon giant dipole resonances in energetic heavy-ion collisions are then evaluated through a semiclassical coupled-channel calculation. It is argued that the variations of the strength of the anharmonic potential should be combined with appropriate changes in the oscillator frequency, in order to keep the giant dipole resonance energy consistent with the experimental value. When this is taken into account, the effects of anharmonicities on the double giant dipole resonance excitation probabilities are small and cannot account for the well-known discrepancy between theory and experiment.

At ultrarelativistic energies the minijet production in heavy-ion collisions becomes sensitive to semihard parton rescatterings in the initial stages of the process. As a result global characteristics of the event, like the initial minijet density, become rather insensitive on the infrared cutoff that separates hard and soft interactions. This allows to define a nearly parameter-free saturation cutoff at which the initial conditions may be computed. As an application we study the centrality dependence of the charged particle multiplicity, which is compared with present BNL Relativistic Heavy-Ion Collider data and predicted at higher energies.

Spectroscopic amplitudes play an important role in nuclear capture reactions. These amplitudes are shown to include both single-particle and polarization effects: the former through their spatial dependence and the latter through their normalization (the spectroscopic factors). Coupled-channels equations are developed for the spectroscopic amplitudes. These equations serve as a convenient starting point for the derivation of several approximations: Hartree, Hartree-Fock, and two different single-particle models. The single-particle models include antisymmetry in different ways, but both miss many-body effects. Therefore, cross sections calculated with either of these models need to be multiplied by the spectroscopic factor.