Two-pion correlations in $\sqrt{s_{\mathrm{NN}}}=130\mathrm{}\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC have been measured over a broad range of pair transverse momentum $k_T$ by the PHENIX experiment at RHIC. The $k_T$ dependent transverse radii are similar to results from heavy-ion collisions at $\sqrt{s_{\mathrm{NN}}}=4.1\mathrm{}$, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii $\left(R_{\mathrm{out}}{/R}_{\mathrm{side}}\right)$ is consistent with unity and independent of $k_T$.

Transverse momentum spectra of electrons from $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=130\mathrm{}\mathrm{GeV}$ have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal ${\mathrm{dN}}_e/dy$ for $p_T>0.8\mathrm{}\mathrm{GeV}/c$ is $0.025\pm 0.004\left(\mathrm{stat}\right)\pm 0.010\left(\mathrm{syst}\right)$ in central collisions, and the corresponding charm cross section is $380\pm 60\left(\mathrm{stat}\right)\pm 200\left(\mathrm{syst}\right)\mu \mathrm{b}$ per binary nucleon-nucleon collision.

The $\mathrm{pp}\to \mathrm{pp}{\pi }^{+}{\pi }^{-}$ reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal $\mathrm{pp}\to {\mathrm{pp}}^{*}\left(1440\right)\to \mathrm{pp}\sigma =pp({\pi }^{+}{\pi }^{-}{)}_{I=\ell =0\mathrm{}}$ as the dominant process as well as significant contributions from $p^{*}\to {\Delta }^{++}{\pi }^{-}\to p\sigma$. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance $\left(3\sigma \right)$ are found.

High energy heavy-ion collisions are proposed as a novel means to constrain stringently the high density (HD) behavior of nuclear symmetry energy. Within an isospin-dependent hadronic transport model, it is shown for the first time that the isospin asymmetry of the HD nuclear matter formed in high energy heavy-ion collisions is uniquely determined by the HD behavior of the nuclear symmetry energy. Experimental signatures in two sensitive probes, i.e., ${\pi }^{-}$ to ${\pi }^{+}$ ratio and neutron-proton differential collective flow, are also investigated.

We measured the strength of the $0_{\mathrm{gs}}^{+}\to 2_1^{+}$ excitations in the radioactive mirror nuclei ${}^{32}\mathrm{Ar}$ and ${}^{32}\mathrm{Si}$ using the techniques of intermediate-energy Coulomb excitation for ${}^{32}\mathrm{Ar}$ and inelastic proton scattering in inverse kinematics for ${}^{32}\mathrm{Si}$. The ${}^{32}\mathrm{Ar}$ measurement, taken together with previously existing Coulomb excitation data for ${}^{32}\mathrm{Si}$, yields the isoscalar and isovector multipole matrix elements for the $0_1^{+}\to 2_1^{+}$ transition between $T=2\mathrm{}$ states in the $A=32\mathrm{}$ system. The proton scattering measurement for ${}^{32}\mathrm{Si}$, when combined with the Coulomb excitation data for this nucleus, yields a ratio of neutron and proton matrix elements, $M_n{/M}_p$, for ${}^{32}\mathrm{Si}$.

Results for the cross section and average angular momentum for complete fusion at energies around the Coulomb barrier are presented for ${}^7\mathrm{Li}$ with ${}^{165}\mathrm{Ho}$. Comparison of the cross sections with a one-dimensional barrier penetration model, using a potential consistent with the measured elastic scattering, showed a reduction above the barrier and an enhancement below it. An increase in the measured average angular momentum, $〈\ell 〉$, above the barrier and its consistency with that obtained from the fusion excitation function for weakly bound nuclei, is reported. These results together with a reanalysis of existing data conclusively demonstrate that the effect of breakup on fusion is coherent, like coupling to any nonelastic channel.

The hypernuclei ${}_{\Lambda }^4\mathrm{He}$ and ${}_{\Lambda }^4\mathrm{H}$ provide important information on the hyperon-nucleon interaction. We present accurate Faddeev-Yakubovsky calculations for the $\Lambda$ separation energies of the $0^{+}$ ground and the $1^{+}$ excited states based on the Nijmegen SC YN interactions. We explicitly take the $\Sigma$ admixture into account. Mass differences of the baryons and the charge dependence of the interaction are considered. The results show that the Nijmegen models cannot predict all separation energies simultaneously hinting to failures of the current interaction models. It is pointed out that the differences of the $\Lambda$ separation energies of ${}_{\Lambda }^4\mathrm{He}$ and ${}_{\Lambda }^4\mathrm{H}$ are interesting observables to probe the YN interaction models.

Measuring Compton scattered photons and recoil neutrons in coincidence, quasifree Compton scattering by the neutron has been investigated at MAMI (Mainz) at ${\theta }_{\gamma }^{\mathrm{lab}}=136\mathrm{}°$ in an energy range from 200 to 400 MeV. From the data a polarizability difference of ${\alpha }_n-{\beta }_n=9.8\mathrm{}\pm 3.6\left(\mathrm{stat}{)}_{-1.1\mathrm{}}^{+2.1\mathrm{}}\right(\mathrm{syst})\pm 2.2(\mathrm{model})$ in units of ${10}^{-4\mathrm{}}{\mathrm{fm}}^3$ has been determined. In combination with the polarizability sum ${\alpha }_n+{\beta }_n=15.2\mathrm{}\pm 0.5$ deduced from photoabsorption data, the first precise results for the neutron electric and magnetic polarizabilities, ${\alpha }_n=12.5\mathrm{}\pm 1.8\left(\mathrm{stat}{)}_{-0.6\mathrm{}}^{+1.1\mathrm{}}\right(\mathrm{syst})\pm 1.1(\mathrm{model})$ and ${\beta }_n=2.7\mathrm{}\mp 1.8\left(\mathrm{stat}{)}_{-1.1\mathrm{}}^{+0.6\mathrm{}}\right(\mathrm{syst})\mp 1.1(\mathrm{model})$, are obtained.

We present a qualitative improvement of the ab initio no-core shell model (NCSM) approach by implementing three-body interaction capability for $p$-shell nuclei. We report the first calculations using three-body effective interactions derived from realistic nucleon-nucleon potentials for ${}^6\mathrm{Li}$, ${}^8\mathrm{Be}$, and ${}^{10}\mathrm{B}$ and demonstrate that the use of three-body effective interactions speeds up the convergence of the NCSM approach. For ${}^{10}\mathrm{B}$, we predict $J^{\pi }{T=1\mathrm{}}^{+}0$ ground state, contrary to the experimental observation of $3^{+}0$, when the $\mathrm{AV}{8}^{\prime }$ potential is used, indicating the need for true three-body forces.

The latest generation $\gamma$-ray detection system, GAMMASPHERE, coupled with the Microball charged-particle detector, has made possible a new class of nuclear lifetime measurement. For the first time differential lifetime measurements free from common systematic errors for over 15 different nuclei ( $>30\mathrm{}$ rotational bands in various isotopes of Ce, Pr, Nd, Pm, and Sm) have been extracted at high spin within a single experiment. This comprehensive study establishes the effective single-particle transition quadrupole moments in the $A\sim 135$ light rare-earth region. Detailed comparisons are made with theoretical calculations using the self-consistent cranked mean-field theory which convincingly demonstrates the validity of the additivity of single-particle quadrupole moments in this mass region.

The longitudinal momentum $\left(P_{\Vert }\right)$ distributions of one- and two-neutron removal fragments ( ${}^{21,22}\mathrm{O}$) of ${}^{23}\mathrm{O}$ from the reaction with a C target at 72 $A$ MeV have been measured for the first time using a new direct time-of-flight method with nearly full acceptance for the breakup fragments. The unexpectedly narrow width of ${}^{21}\mathrm{O}$ ( $115\pm 34\mathrm{MeV}/c$ in FWHM) is consistent with two neutrons occupying the ${2s}_{1/2}$ orbital in ${}^{23}\mathrm{O}$. This indicates modification of core ( ${}^{22}\mathrm{O}$) structure for neutron halolike $\mathrm{sd}$ shell nuclei near the drip line. This also suggests the lowering of the s orbital providing a justification for the $N=16\mathrm{}$ magic number.

We investigate a reformulation of the dynamics of interacting fermion systems in terms of a stochastic extension of time-dependent Hartree-Fock equations. From a path-integral representation of the evolution operator, we show that the exact $N$-body state can be interpreted as a coherent average over Slater determinants evolving in a random mean-field. The imaginary time propagation is also presented and gives a similar scheme which converges to the exact ground state. In addition, the growth of statistical errors is examined to show the stability of this stochastic formulation.

We have made the first clear measurements of rotational damping widths in nuclei. In a mixture of three Yb nuclei, these widths are $300\pm 60\mathrm{keV}$ between 1.2 and 1.5 MeV $\gamma$-ray energy $\left[\sim \right(37–57\left)ħ\right]$. Compound damping and motional narrowing are discussed in connection with these results.

We derive the quantum kinetic equation for a pure gluon plasma, applying the background field and closed-time-path method. The derivation is more general and transparent than earlier works. A term in the equation is found which, as in the classical case, corresponds to the color charge precession for partons moving in the gauge field.

Quark matter at astrophysical densities may contain stable vortices due to the spontaneous breaking of hypercharge symmetry by kaon condensation. We argue that these vortices could be both charged and electrically superconducting. Current carrying loops (vortons) could be long-lived and play a role in the magnetic and transport properties of this matter. We provide a scenario for vorton formation in protoneutron stars.

The transverse mass spectra of $\Omega$, $J/\psi$, and ${\psi }^{\prime }$ in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $158A\mathrm{GeV}$ are studied within a hydrodynamical model of the quark-gluon-plasma expansion and hadronization. The model reproduces the existing data with the common hadronization parameters: temperature ${T=T}_H\cong 170\mathrm{MeV}$ and average collective transverse velocity ${\overline{v}}_T\cong 0.2$.

Photon energy spectra up to the kinematic limit have been measured in 190 MeV proton reactions with light and heavy nuclei to investigate the influence of the multiple-scattering process on the photon production. Relative to the predictions of models based on a quasifree production mechanism, a strong suppression of bremsstrahlung is observed in the low-energy region of the photon spectrum. We attribute this effect to the interference of photon amplitudes due to multiple scattering of nucleons in the nuclear medium.

We observed well-separated $1s$ and $2p$ ${\pi }^{-}$ states in ${}^{205}\mathrm{Pb}$ in the ${}^{206}\mathrm{Pb}\left({d,}^3\mathrm{He}\right)$ reaction at $T_d=604.3\mathrm{}\mathrm{MeV}$. The binding energies and the widths determined are $B_{1s}=6.762\mathrm{}\pm 0.061\mathrm{MeV}$, ${\Gamma }_{1s}={0.764}_{-0.154\mathrm{}}^{+0.171\mathrm{}}\mathrm{MeV}$, $B_{2p}=5.110\mathrm{}\pm 0.045\mathrm{MeV}$, and ${\Gamma }_{2p}{=0.321\mathrm{}}_{-0.062\mathrm{}}^{+0.060\mathrm{}}\mathrm{MeV}$. They are used to deduce the real and imaginary strengths of the $s$-wave part of the pion-nucleus interaction, which translates into a positive mass shift of ${\pi }^{-}$ in ${}^{205}\mathrm{Pb}$.

We have determined the energy of the $J^{\pi }{=1/2\mathrm{}}^{+}$, $T=3/2\mathrm{}$ resonance in ${}^{32}\mathrm{S}(p,p)$ to be $E_p=3374.7\mathrm{}\pm 0.8\mathrm{keV}$. This disagrees with the previously accepted value of $E_p=3370\mathrm{}\pm 1\mathrm{keV}$ by Abbondanno et al. [Nuovo Cimento 70A, 391 (1970)] and solves a problem raised by recent observations of unexpected deviations from the isobaric multiplet mass equation. This resonance is also important in calibrating the $\beta$-delayed proton spectra from ${}^{33}\mathrm{Ar}$ and ${}^{32}\mathrm{Ar}$, and our findings may modify previous conclusions.

Self-consistent quantum approaches are used to study the instabilities of finite nuclear systems. The frequencies of multipole density fluctuations are determined as a function of dilution and temperature for several isotopes. The spinodal region of the phase diagrams is determined, and it appears that instabilities are reduced by finite size effects. The role of surface and volume instabilities is discussed. It is indicated that the important chemical effects associated with mechanical disruption may lead to isospin fractionation.