We describe a double-scattering experiment with a novel tagged neutron beam to measure differential cross sections for $np$ backscattering to better than $\pm 2\%$ absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle dependence constrain the charged pion-nucleon coupling constant, but existing data show serious discrepancies among themselves and with energy-dependent partial-wave analyses. The present results are in good accord with the partial-wave analyses, but deviate systematically from other recent measurements.

The ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction regulates the rate of energy generation in the stellar CN cycle. Because discrepancies have been found in the analysis and interpretation of previous capture data, we have measured the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ excitation function for energies in the range $E_p^{\mathrm{l}\mathrm{a}\mathrm{b}}=155–524\mathrm{k}\mathrm{e}\mathrm{V}$. Fits of these data using $R$-matrix theory yield a value for the $S$ factor at zero energy of $1.68\pm 0.09(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.16(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\mathrm{k}\mathrm{e}\mathrm{V}\mathrm{b}$, which is significantly smaller than the previous result. The corresponding reduction in the stellar reaction rate for ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ has a number of interesting consequences, including an impact on estimates for the age of the Galaxy derived from globular clusters.

The PHENIX experiment has measured midrapidity transverse momentum spectra ($0.4<p_T<4.0\mathrm{G}\mathrm{e}\mathrm{V}/c$) of single electrons as a function of centrality in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$. Contributions from photon conversions and Dalitz decays of light neutral mesons are measured by introducing a thin (1.7% $X_0$) converter into the PHENIX acceptance and are statistically removed. The subtracted nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons containing heavy quarks, mainly charm at lower $p_T$. For all centralities, the charm production cross section is found to scale with the nuclear overlap function, $T_{AA}$. For minimum-bias collisions the charm cross section per binary collision is $N_{c\overline{c}}/T_{AA}=622\pm 57(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 160(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\mu \mathrm{b}$.

We have studied the ${}^2\mathrm{H}({}^8\mathrm{L}\mathrm{i},p){}^9\mathrm{L}\mathrm{i}$ reaction to obtain information on the spins, parities, and single-neutron spectroscopic factors for states in ${}^9\mathrm{L}\mathrm{i}$, using a radioactive ${}^8\mathrm{L}\mathrm{i}$ beam. The deduced properties of the lowest three states are compared to the predictions of a number of calculations for the structure of ${}^9\mathrm{L}\mathrm{i}$. The results of ab initio quantum Monte Carlo calculations are in good agreement with the observed properties.

The nonmesonic weak decay of polarized $\Lambda$ hypernuclei is studied for the first time by taking into account, with a Monte Carlo intranuclear cascade code, the nucleon final state interactions. A one-meson-exchange model is employed to describe the $\overrightarrow{\Lambda }N\to nN$ processes in a finite nucleus framework. The relationship between the intrinsic $\Lambda$ asymmetry parameter $a_{\Lambda }$ and the asymmetry $a_{\Lambda }^{\mathrm{M}}$ accessible in experiments is discussed. A strong dependence of $a_{\Lambda }^{\mathrm{M}}$ on nucleon final state interactions and detection threshold is obtained. Our results for $a_{\Lambda }^{\mathrm{M}}$ are consistent with ${}_{\Lambda }{}^{11}\overrightarrow{\mathrm{B}}$ and ${}_{\Lambda }{}^{12}\overrightarrow{\mathrm{C}}$ data but disagree with observations in ${}_{\Lambda }{}^5\overrightarrow{\mathrm{H}}\mathrm{e}$.

Transport coefficients of gluon plasma are calculated for an SU(3) pure gauge model by lattice QCD simulations on ${16}^3\times 8$ and ${24}^3\times 8$ lattices. Simulations are carried out at slightly above the deconfinement transition temperature $T_c$, where a new state of matter is currently being pursued in BNL RHIC experiments. Our results show that the ratio of the shear viscosity to the entropy is less than one and the bulk viscosity is consistent with zero in the region $1.4\le T/T_c\le 1.8$.

A relativistic coupled-channels theory for the calculation of dissociation cross sections of halo nuclei is developed. A comparison with nonrelativistic models is done for the dissociation of ${}^8\mathrm{B}$ projectiles. It is shown that neglecting relativistic effects leads to sizable inaccuracies in the extraction of the astrophysical $S$ factor for the $\mathrm{\text{proton}}+\mathrm{\text{beryllium}}$ radiative capture reaction.

A measurement of the analyzing power $A_y$ of the $\overrightarrow{p}d\to (pp)+n$ reaction was carried out at the ANKE spectrometer at COSY at beam energies of 0.5 and 0.8 GeV by detection of a fast forward proton pair of small excitation energy $E_{pp}<3\mathrm{M}\mathrm{e}\mathrm{V}$. The $S$-wave dominance in the fast diproton is experimentally demonstrated in this reaction. While at $T_p=0.8\mathrm{G}\mathrm{e}\mathrm{V}$ the measured analyzing power almost vanishes, it rises to nearly unity at $T_p=0.5\mathrm{G}\mathrm{e}\mathrm{V}$ for neutrons emitted at ${\theta }_n^{\mathrm{c}.\mathrm{m}.}=167°$. The results are compared with a model taking into account one-nucleon exchange, single scattering, and $\Delta (1232)$ excitation in the intermediate state. The model describes fairly well the unpolarized cross section obtained earlier and the analyzing power at 0.8 GeV; it fails to reproduce $A_y$ at 0.5 GeV.

Long-standing anomalies in $K^{+}$-nucleus integral cross sections could be resolved by extending the impulse-approximation $t\rho$ optical-potential framework to incorporate $K^{+}$ absorption on pairs of nucleons. Substantially improved fits to the data at $p_{\mathrm{l}\mathrm{a}\mathrm{b}}\sim 500–700\mathrm{M}\mathrm{e}\mathrm{V}/c$ are obtained. An upper bound on the absorption cross section per nucleon is derived, ${\sigma }_{\mathrm{a}\mathrm{b}\mathrm{s}}^{(K^{+})}/A\sim 3.5\mathrm{m}\mathrm{b}$. We conjecture that the underlying microscopic absorption process is $K^{+}nN\to {\Theta }^{+}N$, where ${\Theta }^{+}(1540)$ is the newly discovered exotic $Y=2$, $I=0$, $Z=1$ pentaquark baryon, and estimate that $\sigma (K^{+}d\to {\Theta }^{+}p)$ is a fraction of millibarn. Comments are made on ${\Theta }^{+}$ production reactions on nuclei.

Hydrodynamical modeling of heavy-ion collisions at RHIC suggests that the quark-gluon plasma (QGP) “thermalizes” in a remarkably short time scale, about $0.6\mathrm{f}\mathrm{m}/c$. We argue that this should be viewed as indicating fast isotropization, but not necessarily complete thermalization, of the nonequilibrium QGP. Non-Abelian plasma instabilities can drive local isotropization of an anisotropic QGP on a time scale which is faster than ordinary perturbative scattering processes. As a result, we argue that theoretical expectations based on weak-coupling analysis are not necessarily in conflict with hydrodynamic modeling of the early part of RHIC collisions, provided one recognizes the key role of non-Abelian plasma instabilities.

Polarization observables in the ${}^4\mathrm{H}\mathrm{e}(\overrightarrow{e},e^{\prime }\overrightarrow{p}){}^3\mathrm{H}$ reaction are calculated using accurate three- and four-nucleon bound-state wave functions, a realistic model for the nuclear electromagnetic current operator, and a treatment of final-state interactions with an optical potential. In contrast to earlier studies, no significant discrepancies are found between theory and experiment both for the ratio of transverse to longitudinal polarization transfers and for the induced polarization, when free-nucleon electromagnetic form factors are used in the current operator. The present results challenge the current interpretation of the experimental data in terms of medium-modified form factors.

Midrapidity open charm spectra from direct reconstruction of $D^0(\overline{D^0})\to K^{\mp }{\pi }^{\pm }$ in $d+\mathrm{A}\mathrm{u}$ collisions and indirect electron-positron measurements via charm semileptonic decays in $p+p$ and $d+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$ are reported. The $D^0(\overline{D^0})$ spectrum covers a transverse momentum ($p_T$) range of $0.1<p_T<3\mathrm{G}\mathrm{e}\mathrm{V}/c$, whereas the electron spectra cover a range of $1<p_T<4\mathrm{G}\mathrm{e}\mathrm{V}/c$. The electron spectra show approximate binary collision scaling between $p+p$ and $d+\mathrm{A}\mathrm{u}$ collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at midrapidity for open charm production from $d+\mathrm{A}\mathrm{u}$ collisions at BNL RHIC is $d{\sigma }_{c\overline{c}}^{NN}/dy=0.30\pm 0.04(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.09(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\mathrm{m}\mathrm{b}$. The results are compared to theoretical calculations. Implications for charmonium results in $A+A$ collisions are discussed.

Prompt-fission-neutron multiplicities were measured for ${}^{238}\mathrm{U}(n,f)$ and ${}^{235}\mathrm{U}(n,f)$ from 0.4 to 200 MeV. The data are of great importance in connection with accelerator-coupled nuclear reactor systems incinerating actinides. We report that fission induced by 200 MeV neutrons produces $\approx 10$ more prompt neutrons than fission induced by reactor neutrons. Most neutrons are evaporated from the fission fragments and the prefission compound nucleus, as the preequilibrium emission of energetic neutrons accounts for a maximum of 15% of the prompt neutrons at 200 MeV.

In order to produce a neutron-rich $\Lambda$ hypernucleus for the first time, we carried out an experiment by utilizing the $({\pi }^{-},K^{+})$ double charge-exchange reaction on a ${}^{10}\mathrm{B}$ target. We observed the production of a ${}_{\Lambda }{}^{10}\mathrm{L}\mathrm{i}$ hypernucleus. The cross section for the $\Lambda$ bound region was found to be $11.3\pm 1.9\mathrm{n}\mathrm{b}/\mathrm{s}\mathrm{r}$ with the $1.2\mathrm{G}\mathrm{e}\mathrm{V}/c$ incident momentum, which is compared with the ${}_{\Lambda }{}^{10}\mathrm{B}$ hypernucleus production cross section, $7.8\pm 0.3\mu \mathrm{b}/\mathrm{s}\mathrm{r}$, in the $({\pi }^{+},K^{+})$ reaction with a $1.05\mathrm{G}\mathrm{e}\mathrm{V}/c$ incident momentum beam.

Emission of ${\pi }^{\pm }$, $K^{\pm }$, $\varphi$, and $\Lambda$ was measured in near-central $\mathrm{C}+\mathrm{C}$ and $\mathrm{S}\mathrm{i}+\mathrm{S}\mathrm{i}$ collisions at $158A\mathrm{G}\mathrm{e}\mathrm{V}$ beam energy. Together with earlier data for $p+p$, $\mathrm{S}+\mathrm{S}$, and $\mathrm{P}\mathrm{b}+\mathrm{P}\mathrm{b}$, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as the onset of the formation of coherent systems of increasing size.

A new version of the nuclear shell model unifies the consideration of the discrete spectrum, where the results reproduce the standard shell model, and continuum. The ingredients of the method are the non-Hermitian effective Hamiltonian, energy-dependent one-body and two-body decay amplitudes, and self-consistent treatment of thresholds. The results for helium and oxygen isotope chains reproduce the data well.

We have developed a new method to study the order-to-chaos transition in rotational nuclei. Correlations between successive $\gamma$ rays are used to determine the average complexity of the intermediate levels and thereby the ratio of the interaction potential between levels to the level spacing. The measured ratios, 0.15 to 1.5, span the range from nearly fully ordered to nearly fully chaotic.

We calculate the energy spectrum for ${}^8\mathrm{B}$ dissociation on a Pb target to all orders in the Coulomb and nuclear fields, and show that the slope of $S_{17}(E)$ obtained in previous analyses of Coulomb dissociation data is too steep, due to deficiencies in the conventional first-order analysis that was used. With a more complete theory that avoids the far-field approximation and includes $E2$, nuclear and dynamical projectile polarization, the disagreement between indirect and direct methods for determining the $S_{17}(E)$ slope and the extrapolated $S_{17}(0)$ values is reduced significantly.

Charged-particle pseudorapidity densities are presented for the $d+\mathrm{A}\mathrm{u}$ reaction at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$ with $-4.2\le \eta \le 4.2$. The results, from the BRAHMS experiment at BNL Relativistic Heavy-Ion Collider, are shown for minimum-bias events and 0%–30%, 30%–60%, and 60%–80% centrality classes. Models incorporating both soft physics and hard, perturbative QCD-based scattering physics agree well with the experimental results. The data do not support predictions based on strong-coupling, semiclassical QCD. In the deuteron-fragmentation region the central 200 GeV data show behavior similar to full-overlap $d+\mathrm{A}\mathrm{u}$ results at $\sqrt{s_{NN}}=19.4\mathrm{G}\mathrm{e}\mathrm{V}$.

With an isospin- and momentum-dependent transport model, we find that the degree of isospin diffusion in heavy-ion collisions at intermediate energies is affected by both the stiffness of the nuclear symmetry energy and the momentum dependence of the nucleon potential. Using a momentum dependence derived from the Gogny effective interaction, recent experimental data from NSCL-MSU on isospin diffusion are shown to be consistent with a nuclear symmetry energy given by $E_{\mathrm{s}\mathrm{y}\mathrm{m}}(\rho )\approx 31.6(\rho /{\rho }_0{)}^{1.05}$ at subnormal densities. This leads to a significantly constrained value of about $-550\mathrm{M}\mathrm{e}\mathrm{V}$ for the isospin-dependent part of the isobaric incompressibility of isospin asymmetric nuclear matter.