A 120 MeV ${}^{15}\mathrm{O}$ radioactive ion beam with an intensity on target of $4.5\times {10}^4$ pps has been developed at the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. This beam has been used to study the level structure of ${}^{16}\mathrm{F}$ at low energies via the $p$(${}^{15}\mathrm{O}$, $p$) reaction using the thick target inverse kinematics method on a polyethylene target. The experimental excitation function was analyzed using $R$-matrix calculations. Significantly improved values for the level widths of the four low-lying states in ${}^{16}\mathrm{F}$ are reported. Good agreement with the theoretical spectroscopic factors is also obtained.

A new method is presented for determining event-by-event fluctuations of elliptic flow, $v_2$, using first-order event planes. By studying the event-by-event distributions of $v_2$ observables and first-order event-plane observables, average flow $\langle v_2\rangle$ and event-by-event flow fluctuations can be separately determined, making appropriate allowance for the effects of finite multiplicity and nonflow. The method has been tested with Monte Carlo simulations. The connection between flow fluctuations and fluctuations of the initial-state participant eccentricity is discussed.

Using the light-cone QCD dipole formalism we investigate manifestations of color transparency (CT) and coherence length (CL) effects in electroproduction of longitudinally ($L$) and transversally ($T$) polarized vector mesons. Motivated by forthcoming data from the HERMES experiment we predict both the $A$ and $Q^2$ dependence of the $L/T$ ratios for ${\rho }^0$ mesons produced coherently and incoherently off nuclei. For an incoherent reaction the CT and CL effects add up and result in a monotonic $A$ dependence of the $L/T$ ratio at different values of $Q^2$. In contrast, for a coherent process the contraction of the CL with $Q^2$ causes an effect opposite to that of CT and we expect quite a nontrivial $A$ dependence.

We have determined the spins $J$ of resonances in the ${}^{147}\mathrm{Sm}$($n,\gamma$) reaction by measuring multiplicities of $\gamma$-ray cascades following neutron capture. Using this technique, we were able to determine $J$ values for all but 14 of the 141 known resonances below $E_n=1$ keV, including 41 firm $J$ assignments for resonances whose spins previously were either unknown or tentative. These new spin assignments, together with previously determined resonance parameters, allowed us to extract level spacings ($D_{0,3}=11.76\pm 0.93$ and $D_{0,4}=11.21\pm 0.85$ eV) and neutron strength functions (${10}^4{S}_{0,3}=4.70\pm 0.91$ and ${10}^4{S}_{0,4}=4.93\pm 0.92$) for $J=3$ and 4 resonances, respectively. Furthermore, cumulative numbers of resonances and cumulative reduced neutron widths as functions of resonance energy indicate that very few resonances of either spin have been missed below $E_n=700$ eV. This conclusion is strengthened by the facts that, over this energy range, Wigner distributions calculated using these $D_0$ values agree with the measured nearest-neighbor level spacings to within the experimental uncertainties, and that the ${\Delta }_3$ values calculated from the data also agree with the expected values. Because a nonstatistical effect recently was reported near $E_n=350$ eV from an analysis of ${}^{147}\mathrm{Sm}$($n,\alpha$) data, we divided the data into two regions; $0<E_n<350$ eV and $350<E_n<700$ eV. Using neutron widths from a previous measurement (corrected for new unresolved doublets identified in this work) and published techniques for correcting for missed resonances and for testing whether data are consistent with a Porter-Thomas distribution, we found that the ${\Gamma }_n^0$ distribution for resonances below 350 eV is consistent with the expected Porter-Thomas distribution. However, we found that ${\Gamma }_n^0$ data in the $350<E_n<700$ eV region are inconsistent with a Porter-Thomas distribution, but in good agreement with a ${\chi }^2$ distribution having $\nu ⩾2$ We discuss possible explanations for these observed nonstatistical effects and their possible relation to similar effects previously observed in other nuclides.

Excitation functions for the above-barrier fusion cross sections are measured for the first time for the ${}^7\mathrm{Li}+{}^{28}\mathrm{Si}$ system by two methods—the characteristic γ-ray method and the evaporation α measurement method—in the energy range $E_{\mathrm{lab}}=11.5\text{−}26$ MeV. Experimental results are consistent and agree with each other, and the one-dimensional Barrier Penetration Model (BPM) predictions describe the data well up to twice the Coulomb barrier, but they overestimate the data by about 15–20% at higher energies.

We present results from large-scale shell model calculations of even and odd tin isotopes from ${}^{134}\mathrm{Sn}$ to ${}^{142}\mathrm{Sn}$ with a shell model space defined by the $1f_{7/2}$, $2p_{3/2}$, $0h_{9/2}$, $2p_{1/2}$, $1f_{5/2}$, and $0i_{13/2}$ single-particle orbits. An effective two-body interaction based on modern nucleon-nucleon interactions is employed. The shell model results are in turn analyzed for their pairing content using a generalized seniority approach. Our results indicate that a pairing model picture captures a great deal of the structure and the correlations of the lowest lying states for even and odd isotopes.

The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is of significant importance for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars. A number of reactions using the dynamical and the statistical models of multifragmentation, and the experimental isoscaling observable, are studied to extract information on the density dependence of the symmetry energy. It is observed that the dynamical and the statistical model calculations give consistent results assuming the sequential decay effect in dynamical model to be small. A comparison with several other independent studies is also made to obtain important constraints on the form of the density dependence of the symmetry energy. The comparison rules out an extremely “stiff” and “soft” forms of the density dependence of the symmetry energy with important implications for astrophysical and nuclear physics studies.

The half-life of ${}^{18}\mathrm{Ne}$ has been determined by detecting 1042-keV γ rays in the daughter ${}^{18}\mathrm{F}$ following the superallowed-Fermi ${\beta }^{+}$ decay of samples implanted at the center of the $8\pi \gamma$-ray spectrometer, a spherical array of 20 HPGe detectors. Radioactive ${}^{18}\mathrm{Ne}$ beams were produced on-line, mass-separated, and ionized using an electron-cyclotron-resonance ionization source at the ISAC facility at TRIUMF in Vancouver, Canada. This is the first high-precision half-life measurement of a superallowed Fermi β decay to utilize both a large-scale HPGe spectrometer and the isotope separation on-line technique. The half-life of ${}^{18}\mathrm{Ne}$, 1.6656 ± 0.0019 s, deduced following a 1.4σ correction for detector pulse pile-up, is four times more precise than the previous world average. As part of an investigation into potential systematic effects, the half-life of the heavier isotope ${}^{23}\mathrm{Ne}$ was determined to be 37.11 ± 0.06 s, a factor of 2 improvement over the previous precision.

Based on a Langevin equation coupled with a statistical decay model, we have studied the effect of isospin on the evaporation residue cross section as a probe of nuclear dissipation by calculating the excess of evaporation residues over its standard statistical-model value as a function of viscosity coefficient for ${}^{194}\mathrm{Pb}$, ${}^{200}\mathrm{Pb}$, and ${}^{206}\mathrm{Pb}$ nuclei. Calculations show that a low isospin not only amplifies the dissipation effects on the excess of evaporation residues but also significantly increases the sensitivity of this excess to the nuclear viscosity coefficient. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, it had better choose those compound systems with small isospin.

New results concerning the production of neutral strange particles, $K^0$ and Λ in Ni+Ni collisions at $1.93A$ GeV, measured with the FOPI detector at GSI Darmstadt, are presented. Rapidity density distributions and Boltzmann slope parameter distributions are measured in nearly the full phase space of the reaction. The observables are compared to existing $K^{+}$ and proton data. While the $K^0$ data agree with previously reported $K^{+}$ measurements, the Λ distributions show a different behavior relative to that of protons. The strangeness balance and the production yield per participating nucleon as a function of the centrality of the reaction are discussed, for the first time at GSI Schwerionen Synchrotron (SIS) energies.

A partial-wave analysis of $NN$ elastic scattering data has been updated to include a number of recent measurements. Experiments carried out at the Cooler Synchrotron (COSY) by the EDDA Collaboration have had a significant impact above 1 GeV. Results are discussed in terms of the partial-wave and direct-reconstruction amplitudes.

Excited states in ${}^{82}\mathrm{Ge}$, populated in the spontaneous fission of ${}^{248}\mathrm{Cm}$, have been studied by means of prompt γ spectroscopy, using the EUROGAM2 multidetector array. The known level at 2287 keV is assigned spin and parity $4^{+}$. Two new excited levels in ${}^{82}\mathrm{Ge}$, with spins and parities $5,6^{+}$, are proposed at 2930 and 3228 keV. At least one of the new levels is expected to be be due to neutron excitations across the $N=50$ shell gap. Its low energy, as compared to heavier $N=50$ isotones, supports the suggestion of other works that the $N=50$ shell closure is weakening when approaching the expected double shell closure at ${}^{78}\mathrm{Ni}$.

The latest compilation gives the width of the $1/2^{+},T=3/2$ level of ${}^{11}\mathrm{B}$ as 210(20) keV. This is based in part on the value 230(65) keV obtained from fitting ${}^{10}\mathrm{Be}$($p,{\gamma }_0$)${}^{11}\mathrm{B}$ data. It has recently been claimed that these data can be adequately fitted with a width of 640 keV. We discuss this claim and refit the data. With noninterfering levels, a width of order 400 keV is found. A poorer fit in which a second $1/2^{+}$ level is included gives a width of order 600 keV.

We observed single and double proton emissions in the ${}^{14}\mathrm{O}+{}^4\mathrm{He}$ interaction by the thick target inverse kinematic (TTIK) method at initial energy for ${}^{14}\mathrm{O}$ at 32.7 MeV. We found that the protons mainly originate from the resonance excitation of states in ${}^{18}\mathrm{Ne}$. The observed states in ${}^{18}\mathrm{Ne}$ decay by protons mainly to proton unstable states in ${}^{17}\mathrm{F}$. It was found that the decay of a state in ${}^{18}\mathrm{Ne}$ at $E_{\mathrm{ex}}=8.45$ MeV demonstrates the features of a decay by a correlated proton pair. The observed properties of the ${}^{14}\mathrm{O}+{}^4\mathrm{He}$ interaction make a previous interpretation for the rate of ${}^{14}\mathrm{O}$(${}^4\mathrm{He}$, $p$)${}^{17}\mathrm{F}$ at astrophysical energies suspect. We show how the TTIK method should be modified to obtain the data of astrophysical interest.

We show that the centrality and system-size dependence of elliptic flow measured at the BNL Relativistic Heavy Ion Collider (RHIC) are fully described by a simple model based on eccentricity scaling and incomplete thermalization. We argue that the elliptic flow is at least 25% below the (ideal) “hydrodynamic limit,” even for the most central Au-Au collisions. This lack of perfect equilibration allows for estimates of the effective parton cross section in the quark-gluon plasma and of its viscosity to entropy density ratio. We also show how the initial conditions affect the transport coefficients and thermodynamic quantities extracted from the data, in particular, the viscosity and the speed of sound.

Within the context of a nonrelativistic semiclassical distorted wave (SCDW) model, we demonstrate that the experimentally observed reduction of the inclusive quasielastic ${}^{208}\mathrm{Pb}$($\overrightarrow{p},p^{\text{'}}$) analyzing power relative to the value for free $NN$ scattering, at incident laboratory kinetic energies of 290 and 200 MeV and at the centroid of the quasielastic peak, is mainly attributed to nuclear medium modifications of the $NN$ effective interaction and also nuclear distortion effects on the scattering wave functions. In addition, the SCDW model also provides a satisfactory quantitative description of the unpolarized double differential cross section.

Multinucleon transfer reactions in ${}^{40}\mathrm{Ca}+{}^{96}\mathrm{Zr}$ and ${}^{90}\mathrm{Zr}+{}^{208}\mathrm{Pb}$ have been measured at energies close to the Coulomb barrier in a high-resolution γ-particle coincidence experiment. The large-solid-angle magnetic spectrometer PRISMA coupled to the CLARA γ array has been employed. Trajectory reconstruction has been applied for the complete identification of transfer products. Mass and charge yields, total kinetic energy losses, γ transitions of the binary reaction partners, and comparison of data with semiclassical calculations are reported. Specific transitions in ${}^{95}\mathrm{Zr}$ populated in one-particle transfer channels are discussed in terms of particle-phonon couplings. The γ decays from states in ${}^{42}\mathrm{Ca}$ in the excitation energy region expected from pairing vibrations are also observed.

In a recent article, we calculated fusion cross sections for systems involving even-even nuclei based on a method that takes into account the couplings to a complete set of states for surface vibrations of the nuclear densities. The predictions were obtained without using any adjustable parameter, and are in good agreement with the experimental results for most of the systems, even at sub-barrier energies. In the present work, we extend these calculations to systems involving nuclei with odd number of protons and/or of neutrons.

Photoproduction of the cascade resonances has been investigated in the reactions $\gamma p\to K^{+}{K}^{+}(X)$ and $\gamma p\to K^{+}{K}^{+}{\pi }^{-}(X)$. The mass splitting of the ground state (${\Xi }^{-},{\Xi }^0$) doublet is measured to be $5.4\pm 1.8$ MeV/$c$${}^2$, consistent with existing measurements. The differential (total) cross sections for the ${\Xi }^{-}$ have been determined for photon beam energies from 2.75 to 3.85 (4.75) GeV and are consistent with a production mechanism of $Y^{*}\to K^{+}{\Xi }^{-}$ through a $t$-channel process. The reaction $\gamma p\to K^{+}{K}^{+}{\pi }^{-}[{\Xi }^0]$ has also been investigated to search of excited cascade resonances. No significant signal of excited cascade states other than the ${\Xi }^{-}(1530)$ is observed. The cross-section results of the ${\Xi }^{-}(1530)$ have also been obtained for photon beam energies from 3.35 to 4.75 GeV.

We perform a model-independent phenomenological analysis of experimental data on proton form factor ratio. We find that only one of the two-photon exchange amplitudes, which we call $\delta {\mathcal{G}}_M$, is responsible for the discrepancy between Rosenbluth and polarization methods. The linearity of Rosenbluth plots implies that $\delta {\mathcal{G}}_M$ is approximately linear function of ɛ. The slope of $\delta {\mathcal{G}}_M$ is extracted from experimental data and is shown to be consistent with theoretical calculations.