Cross sections were measured for the near-threshold electrodisintegration of ${}^3\mathrm{He}$ at momentum transfer values of $q=2.4,$ $4.4,$ and $4.7{\mathrm{fm}}^{-1}.$ From these and prior measurements the transverse and longitudinal response functions $R_T$ and $R_L$ were deduced. Comparisons are made against previously published and new nonrelativistic $A=3\mathrm{}$ calculations using the best available nucleon-nucleon NN potentials. In general, for $q<\mathrm{}2\mathrm{}{\mathrm{fm}}^{-1}$ these calculations accurately predict the threshold electrodisintegration of ${}^3\mathrm{He}.$ Agreement at increasing q demands consideration of two-body terms, but discrepancies still appear at the highest momentum transfers probed, perhaps due to the neglect of relativistic dynamics, or to the underestimation of high-momentum wave-function components.

We address the problem of a possible nonlocality in the nucleon-nucleon interaction and its consequences for the description of the three-nucleon bound states ${}^3\mathrm{H}$ and ${}^3\mathrm{He}.$ A nucleon-nucleon potential model is constructed, which respects the local behavior of traditional nucleon-nucleon interactions at longer ranges but exhibits a nonlocality at shorter distances. It provides for an accurate fit of all existing nucleon-nucleon data and takes into account breaking of charge independence and charge symmetry. With this interaction model the ${}^3\mathrm{H}$ and ${}^3\mathrm{He}$ binding energies can be described simultaneously in perfect agreement with experimental data. No three-nucleon force is needed as in the case of purely local nucleon-nucleon potentials.

Intermediate energy Coulomb excitation at 100 MeV/nucleon was used to probe the low-lying level structure of both ${}^{18}\mathrm{O}$ and ${}^{20}\mathrm{O}$ in the region between 1 and 8 MeV. Discrete $1^{-}$ states with energies of 5.35(10) and 6.85(5) MeV were observed in ${}^{20}\mathrm{O}.$ The strong direct excitation and subsequent $\gamma$-ray decay of these states, along with $B\left(E\lambda \right)$ predictions for ${}^{18,20}\mathrm{O}$ levels in this energy region, established their dipole character. The extracted $B\left(E1\mathrm{}\right)\mathrm{}\uparrow$ values of ${0.062\left(16\right)e}^2{\mathrm{fm}}^2$ and ${0.035\left(9\right)e}^2{\mathrm{fm}}^2$ for the 5.35- and 6.85-MeV states, respectively, are significantly larger than shell model calculations, though modification of the single-particle energies, in particular, the $p-\mathrm{sd}$ shell gap, improves the agreement. The summed $B\left(E1\mathrm{}\right)\mathrm{}\uparrow$ value for these levels (in Weisskopf units) is consistent with that for other nuclei that have been discussed recently in the literature as potential Pygmy dipole resonance hosts.

The excited states of a ${}^{78}\mathrm{Se}$ nucleus were studied via a multiple Coulomb excitation experiment. A natural lead target was irradiated by the ${}^{78}\mathrm{Se}$ beam and $\gamma$ rays in coincidence with the scattered projectiles were collected. Resulting yields were used as an input for the least squares analysis code GOSIA. Four known excited states were observed and nine matrix elements including three diagonal ones were derived from this analysis. The deformation parameter $〈Q^2〉$ was deduced by a sum rule. The results showed good agreement with the calculation by the asymmetric rotor model with triaxial deformation parameter $\gamma \simeq 23°–28°.$ The quadrupole moments of the $2_1^{+}$ and $2_2^{+}$ states analyzed by this model suggested that both levels had the same intrinsic state.

We consider a soluble model of multifragmentation which is similar in spirit to many models that have been used to fit intermediate energy heavy-ion collision data. We draw a $p-V$ diagram for the model and compare with a $p-V$ diagram obtained from a mean-field theory. We investigate the question of chemical instability in the multifragmentation model. Phase transitions in the model are discussed.

We apply continuum percolation to proton-proton collisions and look for the possible threshold to phase transition from confined nuclear matter to quark-gluon plasma. Making the assumption that $J/\psi$ suppression is a good signal to the transition, we discuss this phenomenon for $\mathrm{pp}$ collisions, in the framework of a dual model with strings.

The ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction plays a central role in the evaluation of solar neutrino fluxes. We report on a new precision measurement of the cross section of this reaction, following our previous experiment with an implanted ${}^7\mathrm{Be}$ target, a raster-scanned beam, and the elimination of backscattering losses. The new measurement incorporates a higher activity ${}^7\mathrm{Be}$ target and a number of improvements in design and procedure. The cross section at a selected energy $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=850\mathrm{}\mathrm{keV}$ (where c.m. stands for center of mass) was measured several times under varying experimental conditions, yielding a value of $S_{17}{(E}_{\mathrm{c}.\mathrm{m}.\mathrm{}}=850\mathrm{}\mathrm{keV})=24.0\mathrm{}\pm 0.5\mathrm{eV}\mathrm{}\mathrm{b},$ to serve as a benchmark. Measurements were carried out at lower energies as well. Due to the precise knowledge of the implanted ${}^7\mathrm{Be}$ density profile, it was possible to reconstitute both the off- and on-resonance parts of the cross section and to obtain from the entire set of measurements an extrapolated value of $S_{17}\mathrm{}\left(0\right)=21.2\mathrm{}\pm 0.7\mathrm{eV}\mathrm{}\mathrm{b},$ using the cluster model of Descouvemont and Baye.

The energy per particle of zero-temperature neutron matter is investigated, with particular emphasis on the role of the $\mathit{L}\cdot \mathit{S}$ interaction. An analysis of the importance of explicit spin-orbit correlations in the description of the system is carried out by the auxiliary field diffusion Monte Carlo method. The improved nodal structure of the guiding function, constructed by explicitly considering these correlations, lowers the energy. The proposed spin-backflow orbitals can also be conveniently used in the Green’s function Monte Carlo calculations of light nuclei.

We derive an analytical expression for the quenching factor in the strong quenching limit where the $p_T$ spectrum of hard partons is dominated by surface emission. We explore the phenomenological consequences of different scaling laws for the energy loss and calculate the additional suppression of the away-side jet.

Asymptotic normalization coefficients (ANCs) for ${}^8{\overrightarrow{\mathrm{Li}}}^7\mathrm{Li}+n$ have been extracted from the neutron transfer reaction ${}^{13}\mathrm{C}{(}^7\mathrm{Li}{,}^8\mathrm{Li}{)}^{12}\mathrm{C}$ at 63 MeV. These are related to the ANCs in ${}^8{\overrightarrow{\mathrm{B}}}^7\mathrm{Be}+p$ using charge symmetry. We extract ANCs for ${}^8\mathrm{B}$ which are in very good agreement with those inferred from proton transfer and breakup experiments. We have also separated the contributions from the $p_{1/2}$ and $p_{3/2}$ components in the transfer. We find the astrophysical factor for the ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction to be $S_{17}\mathrm{}\left(0\right)=17.6\mathrm{}\pm 1.7\mathrm{eV}\mathrm{}\mathrm{b}.$ This is the first time that the rate of a direct capture reaction of astrophysical interest has been determined through a measurement of the ANCs in the mirror system.

We have made new, improved measurements of the ${}^{28–30}\mathrm{Si}$ $(n,\gamma )$ cross sections and have done a resonance analysis of these data including previous total cross sections. Together with the calculated contributions due to direct capture, we calculated the astrophysical $(n,\gamma )$ reaction rates and investigated the s-process abundances of the Si isotopes. Measured isotopic anomalies of intermediate and heavy elements in SiC grains from meteorites appear to be attributable to the s-process in asymptotic giant branch (AGB) stars. But the Si isotopic ratios in these grains are substantially different than s-process models predict. Therefore, recent papers have invoked galactic chemical evolution or other effects to explain the Si isotope ratios in these grains. Our new reaction rates are significantly different than previous rates, and s-process calculations using these rates lead to much larger isotopic shifts in ${}^{30}\mathrm{Si}.$ However, these exploratory calculations demonstrate that even with these substantially different rates the large observed variation in SiC grain from AGB stars cannot be explained by standard s-process models.

The influence of the magnetic moment interaction of nucleons on nucleon-deuteron elastic scattering and breakup cross sections and on elastic scattering polarization observables has been studied. Among the numerous elastic scattering observables only the vector analyzing powers were found to show a significant effect, and of opposite sign for the proton-deuteron and neutron-deuteron systems. This finding results in an even larger discrepancy than the one previously established between neutron-deuteron data and theoretical calculations. For the breakup reaction the largest effect was found for the final-state-interaction cross sections. The consequences of this observation on previous determinations of the ${}^1{S}_0$ scattering lengths from breakup data are discussed.

We apply the point form of relativistic quantum mechanics to develop a Poincaré invariant coupled-channel formalism for two-particle systems interacting via one-particle exchange. This approach takes the exchange particle explicitly into account and leads to a generalized eigenvalue equation for the Bakamjian-Thomas type mass operator of the system. The coupling of the exchange particle is derived from quantum field theory. As an illustrative example we consider vector mesons within the chiral constituent quark model in which the hyperfine interaction between the confined quark-antiquark pair is generated by Goldstone-boson exchange. We study the effect of retardation in the Goldstone-boson exchange by comparing with the commonly used instantaneous approximation. As a nice physical feature we find that the problem of a too large ρ-ω splitting can nearly be avoided by taking the dynamics of the exchange meson explicitly into account.

For even-even nuclei, it is shown that the predicted $B\left(E2\mathrm{}\right)\mathrm{}$ values from the odd spin states of the quasi-$\gamma$ band in a $\gamma$-soft nucleus to the yrast band are quite similar to those predicted for the one-phonon wobbling mode of a rigidly triaxial nucleus. This suggests that the observation of wobbling points to axial asymmetry, but not necessarily to rigid triaxiality. However, another observable that does distinguish $\gamma$-soft from $\gamma$-rigid structure is identified.

New levels in the neutron-rich ${}^{113}\mathrm{Ru}$ nucleus have been identified by analyzing $\gamma -\gamma -\gamma$ coincidence events following the spontaneous fission of ${}^{252}\mathrm{Cf}$ with the Gammasphere detector array. A rotational band going up to 3.6 MeV is identified and is proposed to be built on the intruder $\nu {\mathrm{h}}_{11/2}$ orbital going up to $\mathrm{}(31/2)\mathrm{}ħ.$ A few states of a possible signature partner are also observed.

The electric quadrupole moment Q for the ground state of ${}^{17}\mathrm{B}$ was determined by the $\beta$-NMR method applied to spin-polarized projectile fragments. From the measured quadrupole coupling constant, $|{eqQ/h(}^{17}\mathrm{B}\mathrm{in}\mathrm{}\mathrm{Mg})|=137.4\mathrm{}\pm 4.5\mathrm{kHz},$ for ${}^{17}\mathrm{B}$ in a Mg single crystal stopper the Q moment was deduced as $|{Q(}^{17}\mathrm{B})|=38.6\mathrm{}\pm 1.5\mathrm{mb}.$ As was the case in the previous ${}^{15}\mathrm{B}$ result, the obtained Q moment is very close to that for the $N=8\mathrm{}$ isotope ${}^{13}\mathrm{B},$ in sharp contrast to the results of conventional shell-model calculations using constant effective charges. Comparison of the shell-model calculations indicates substantial reduction of the $E2\mathrm{}$ effective charges for isotopes with large $\left(N-Z\right)/A$ ratios. The results were well accounted for in terms of $\left(N-Z\right)/A$ dependent $E2\mathrm{}$ polarization charges as predicted by Bohr and Mottelson and by incorporating the decoupling feature of loosely bound particles.

We present the evidence for the existence of a universal scaling behavior of the production of ${\pi }^0$ at all transverse momenta in heavy-ion collisions at all centralities and all collision energies. The corresponding scaling behavior of the quarks is then derived just before the quarks recombine with antiquarks to form the pions. The degradation effect of the dense medium on the quark $p_T$ is derived from the scaling distribution. In the recombination model it is then possible to calculate the $p_T$ distributions of the produced proton and kaon, which are scaling also. Experimentally verifiable predictions are made. Implications of the existence of the scaling behavior are discussed.

Within an effective Lagrangian model, we present calculations for cross sections of the dilepton production in proton-proton and proton-neutron collisions at laboratory kinetic energies in 1–5 GeV range. Production amplitudes include contributions from the nucleon-nucleon bremsstrahlung as well as from the mechanism of excitation, propagation, and radiative decay of $\Delta \mathrm{}\left(1232\right)\mathrm{}$ and $N^{*}\mathrm{}\left(1520\right)\mathrm{}$ intermediate baryonic resonances. It is found that the delta isobar terms dominate the cross sections in the entire considered beam energy range. Our calculations are able to explain the data of the DLS Collaboration on the dilepton production in proton-proton collisions for beam energies below 1.3 GeV. However, for incident energies higher than this the inclusion of contributions from other dilepton sources such as Dalitz decay of ${\pi }^0$ and $\eta$ mesons, and direct decay of ${\rho }^0$ and $\omega$ mesons is necessary to describe the data.

The ${}^6\mathrm{Li}(p,\alpha {)}^3\mathrm{He}$ reaction has been studied from $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=2.4\mathrm{}\mathrm{MeV}$ down to astrophysical energies by means of the indirect Trojan horse method applied to the ${}^2\mathrm{H}{(}^6\mathrm{Li},\alpha$ ${}^3\mathrm{He})$ n three-body reaction performed at an incident energy of 25 MeV. Coincidence spectra measured in a kinematically complete experiment show the presence of the quasifree ${}^6\mathrm{Li}-p$ process. The excitation function for this process was extracted from the three-body reaction cross section at low neutron momentum and compared with the behavior of the free two-body reaction cross section.

The ${}^{14}\mathrm{N}(p,\gamma {)}^{15}\mathrm{O}$ reaction, which controls energy production in the CNO cycle, has contributions from both resonance and direct captures to the ground and excited states. The overall normalization of the direct captures is defined by the corresponding asymptotic normalization coefficients (ANCs). Especially important is the ANC for the subthreshold state in ${}^{15}\mathrm{O}$ at $-0.504\mathrm{keV}$ since direct capture through this state dominates the reaction rate at stellar energies. In order to determine the ANCs for ${}^{14}\mathrm{N}+p^{15}\mathrm{O},$ the ${}^{14}\mathrm{N}{(}^3\mathrm{He}{,d)}^{15}\mathrm{O}$ proton transfer reaction has been measured at an incident energy of 26.3 MeV. Angular distributions for proton transfer to the ground and five excited states were obtained. ANCs were then extracted from comparison to both distorted-wave Born approximation and coupled-channels Born approximation calculations. Using these ANCs, we calculated the astrophysical factor and reaction rates for ${}^{14}\mathrm{N}(p,\gamma {)}^{15}\mathrm{O}.$ Our analysis favors a low value for the astrophysical factor.