Using resonant laser ionization, $\beta$-decay studies, and for the first time mass measurements, three $\beta$-decaying states have been unambiguously identified in ${}^{70}\mathrm{Cu}$. A mass excess of $-62976.1(1.6)\mathrm{keV}$ and a half-life of 44.5(2) s for the $(6^{-})$ ground state have been determined. The level energies of the $(3^{-})$ isomer at 101.1(3) keV with $T_{1/2}=33(2)\mathrm{s}$ and the $1^{+}$ isomer at 242.4(3) keV with $T_{1/2}=6.6(2)\mathrm{s}$ are confirmed by high-precision mass measurements. The low-lying levels of ${}^{70}\mathrm{Cu}$ populated in the decay of ${}^{70}\mathrm{Ni}$ and in transfer reactions compare well with large-scale shell-model calculations, and the wave functions appear to be dominated by one proton–one neutron configurations outside the closed $Z=28$ shell and $N=40$ subshell. This does not apply to the $1^{+}$ state at 1980 keV which exhibits a particular feeding and deexcitation pattern not reproduced by the shell-model calculations.

We report results on $\rho (770{)}^0\to {\pi }^{+}{\pi }^{-}$ production at midrapidity in $p+p$ and peripheral $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$. This is the first direct measurement of $\rho (770{)}^0\to {\pi }^{+}{\pi }^{-}$ in heavy-ion collisions. The measured ${\rho }^0$ peak in the invariant mass distribution is shifted by $\sim 40\mathrm{M}\mathrm{e}\mathrm{V}/c^2$ in minimum bias $p+p$ interactions and $\sim 70\mathrm{M}\mathrm{e}\mathrm{V}/c^2$ in peripheral $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions. The ${\rho }^0$ mass shift is dependent on transverse momentum and multiplicity. The modification of the ${\rho }^0$ meson mass, width, and shape due to phase space and dynamical effects are discussed.

We calculate the modification of the effective interaction of particles on the Fermi surface due to polarization contributions, with particular attention to spin-dependent forces. In addition to the standard spin-spin, tensor, and spin-orbit forces, spin nonconserving effective interactions are induced by screening in the particle-hole channels. Furthermore, a novel long-wavelength tensor force is generated. We compute the polarization contributions to second order in the low-momentum interaction $V_{\mathrm{l}\mathrm{o}\mathrm{w}k}$ and find that the medium-induced spin-orbit interaction leads to a reduction of the ${}^{3}P_2$ pairing gap for neutrons in the interior of neutron stars.

Detailed studies of the azimuthal dependence of the mean fragment and flow energies in the $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ and $\mathrm{X}\mathrm{e}+\mathrm{C}\mathrm{s}\mathrm{I}$ systems are reported as a function of incident energy and centrality. Comparisons between data and model calculations show that the flow energy values along different azimuthal directions could be viewed as snapshots of the fireball expansion with different exposure times. For the same number of participating nucleons more transversally elongated participant shapes from the heavier system produce less collective transverse energy. Good agreement with Boltzmann-Uehling-Uhlenbeck calculations is obtained for a soft nuclear equation of state.

We present fission-barrier-height calculations for nuclei throughout the periodic table based on a realistic macroscopic-microscopic model. Compared to other calculations (i) we use a deformation space of a sufficiently high dimension, sampled densely enough to describe the relevant topography of the fission potential, (ii) we unambiguously find the physically relevant saddle points in this space, and (iii) we formulate our model so that we obtain continuity of the potential energy at the division point between a single system and separated fission fragments or colliding nuclei, allowing us to (iv) describe both fission-barrier heights and ground-state masses throughout the periodic table.

Recent experimental characterization of the subshell closure at $N=32$ in the Ca, Ti, and Cr isotones has stimulated shell-model calculations that indicated the possibility that the $N=34$ isotones of these same elements could exhibit characteristics of a shell closure, namely, a high energy for the first excited $2^{+}$ level. To that end, we have studied the decay of ${}^{56}\mathrm{S}\mathrm{c}$ produced in fragmentation reactions and identified new $\gamma$ rays in the daughter $N=34$ isotone ${}^{56}\mathrm{T}\mathrm{i}$. The first $2^{+}$ level is found at an energy of 1127 keV, well below the expected position that would indicate the presence of an $N=34$ shell closure in ${}^{56}\mathrm{T}\mathrm{i}$.

Deeply bound $1s$ states of ${\pi }^{-}$ in ${}^{115,119,123}\mathrm{S}\mathrm{n}$ were preferentially observed using the $\mathrm{S}\mathrm{n}(d,{}^3\mathrm{H}\mathrm{e})$ pion-transfer reaction under the recoil-free condition. The $1s$ binding energies and widths were precisely determined and were used to deduce the isovector parameter of the $s$-wave pion-nucleus potential to be $b_1=-(0.115\pm 0.007)m_{\pi }^{-1}$. The observed enhancement of $|b_1|$ over the free $\pi N$ value ($b_1^{\mathrm{f}\mathrm{r}\mathrm{e}\mathrm{e}}/b_1=0.78\pm 0.05$) indicates a reduction of the chiral order parameter, $f_{\pi }^{*}(\rho {)}^2/f_{\pi }^2\approx 0.64$, at the normal nuclear density, $\rho ={\rho }_0$.

A novel mechanism of $H^0$ and strangelet production in hadronic interactions within the Gribov-Regge approach is presented. In this approach the $H^0$ is produced by the same mechanism as usual hadrons, namely, by disintegration of the remnant formed by the exchange of pomerons between the two protons. Rapidity and transverse momentum spectra of the observed hadrons are well described in this approach. In contrast to traditional distillation approaches, here the production of multiple (strange) quark bags does not require large baryon densities or a quark gluon plasma. We calculate the rapidity and transverse momentum distributions as well as the $4\pi$ multiplicity of the $H^0$ for $\sqrt{s}=17\mathrm{G}\mathrm{e}\mathrm{V}$ (Super Proton Synchrotron) and 200 GeV (Relativistic Heavy Ion Collider). In both cases the $H^0$, if it exists, should be observable by the present experiments.

After 50 years of its prediction, the highest-lying $[202]3/2$ orbit among the six Nilsson single-particle orbits originating from the $sd$ shells in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in ${}^{25}\mathrm{A}\mathrm{l}$ at excitation energies of 6–7.5 MeV in a high-resolution ${}^{25}\mathrm{M}\mathrm{g}({}^3\mathrm{H}\mathrm{e},t)$ charge-exchange reaction at $0°$ having a strong selectivity for Gamow-Teller transitions. In the comparison with the analogous $M1$ transitions in ${}^{25}\mathrm{M}\mathrm{g}$, the $J^{\pi }=3/2^{+}$ bandhead state and the excited $5/2^{+}$ and $7/2^{+}$ members were clearly assigned.

We report the first observations of the first harmonic (directed flow, $v_1$) and the fourth harmonic ($v_4$), in the azimuthal distribution of particles with respect to the reaction plane in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at the BNL Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow ($v_2$) generated at RHIC. From the correlation of $v_2$ with $v_1$ it is determined that $v_2$ is positive, or in-plane. The integrated $v_4$ is about a factor of 10 smaller than $v_2$. For the sixth ($v_6$) and eighth ($v_8$) harmonics upper limits on the magnitudes are reported.

The electric quadrupole transition from the first $2^{+}$ state to the ground $0^{+}$ state in ${}^{16}\mathrm{C}$ is studied through measurement of the lifetime by a recoil shadow method applied to inelastically scattered radioactive ${}^{16}\mathrm{C}$ nuclei. The measured mean lifetime is $77\pm 14(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 19(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\mathrm{p}\mathrm{s}$. The central value of mean lifetime corresponds to a $B(E2;2_1^{+}\to 0^{+})$ value of $0.63e^2{\mathrm{f}\mathrm{m}}^4$, or $0.26$ Weisskopf units. The transition strength is found to be anomalously small compared to the empirically predicted value.

Using symmetric ${}^{112}\mathrm{S}\mathrm{n}+{}^{112}\mathrm{S}\mathrm{n}$, ${}^{124}\mathrm{S}\mathrm{n}+{}^{124}\mathrm{S}\mathrm{n}$ collisions as references, we probe isospin diffusion in peripheral asymmetric ${}^{112}\mathrm{S}\mathrm{n}+{}^{124}\mathrm{S}\mathrm{n}$, ${}^{124}\mathrm{S}\mathrm{n}+{}^{112}\mathrm{S}\mathrm{n}$ systems at an incident energy of $E/A=50\mathrm{M}\mathrm{e}\mathrm{V}$. Isoscaling analyses imply that the quasiprojectile and quasitarget in these collisions do not achieve isospin equilibrium, permitting an assessment of isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical observables, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state.

We have measured the ${}^3\mathrm{H}\mathrm{e}(e,e^{\prime }pp)n$ reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for “fast” nucleons ($p>250\mathrm{M}\mathrm{e}\mathrm{V}/c$) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast $pp$ and $pn$ pairs are back to back with little momentum along the three-momentum transfer, indicating that they are spectators. Calculations by Sargsian and by Laget also indicate that we have measured distorted two-nucleon momentum distributions by striking one nucleon and detecting the spectator correlated pair.

Puzzling discrepancies between recent pion interferometry data on $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ reactions at $\sqrt{s}=130$ and $200A\mathrm{G}\mathrm{e}\mathrm{V}$ from RHIC and predictions based on ideal hydrodynamics are analyzed in terms of covariant parton transport theory. The discrepancies in the $R_{\mathrm{o}\mathrm{u}\mathrm{t}}/R_{\mathrm{s}\mathrm{i}\mathrm{d}\mathrm{e}}$ ratio are significantly reduced when the finite opacity of the gluon plasma is taken into account. However, the magnitude of the radii is not well accounted for.

We present STAR measurements of the azimuthal anisotropy parameter $v_2$ and the binary-collision scaled centrality ratio $R_{\mathrm{C}\mathrm{P}}$ for kaons and lambdas ($\Lambda +\overline{\Lambda }$) at midrapidity in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$. In combination, the $v_2$ and $R_{\mathrm{C}\mathrm{P}}$ particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish $p_T\approx 5\mathrm{G}\mathrm{e}\mathrm{V}/c$ as the value where the centrality dependent baryon enhancement ends. The $K_S^0$ and $\Lambda +\overline{\Lambda }$ $v_2$ values are consistent with expectations of constituent-quark-number scaling from models of hadron formation by parton coalescence or recombination.

The electric form factor of the neutron was determined from measurements of the $\overrightarrow{d}(\overrightarrow{e},e^{\prime }n)p$ reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (${}^{15}\mathrm{N}\mathrm{D}_3$) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find $G_E^n=0.0526\pm 0.0033(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.0026(\mathrm{s}\mathrm{y}\mathrm{s})$ and $0.0454\pm 0.0054\pm 0.0037$ at $Q^2=0.5$ and $1.0(\mathrm{G}\mathrm{e}\mathrm{V}/c{)}^2$, respectively.

Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-$p_T$ pions ($p_T>1\mathrm{G}\mathrm{e}\mathrm{V}/c$) have been measured close to midrapidity in $158A\mathrm{G}\mathrm{e}\mathrm{V}/c$ $\mathrm{P}\mathrm{b}+\mathrm{A}\mathrm{u}$ collisions by the CERES experiment. Elliptic flow ($v_2$) rises linearly with $p_T$ to a value of about $10\%$ at $2\mathrm{G}\mathrm{e}\mathrm{V}/c$. Beyond $p_T\approx 1.5\mathrm{G}\mathrm{e}\mathrm{V}/c$, the slope decreases considerably, possibly indicating a saturation of $v_2$ at high $p_T$. Two-pion azimuthal anisotropies for $p_T>1.2\mathrm{G}\mathrm{e}\mathrm{V}/c$ exceed the elliptic flow values by about $60\%$ in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

We investigate transverse hadron spectra from relativistic nucleus-nucleus collisions within two independent transport approaches that are based on quark, diquark, string, and hadronic degrees of freedom. Both transport models show their reliability for elementary $pp$ as well as light-ion ($\mathrm{C}+\mathrm{C}$, $\mathrm{S}\mathrm{i}+\mathrm{S}\mathrm{i}$) reactions. However, for central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ ($\mathrm{P}\mathrm{b}+\mathrm{P}\mathrm{b}$) collisions above $\sim 5A\mathrm{G}\mathrm{e}\mathrm{V}$ the measured $K^{\pm }$ transverse mass spectra have a larger inverse slope parameter than expected from the calculation. Thus, the pressure generated by hadronic interactions in the transport models above $\sim 5A\mathrm{G}\mathrm{e}\mathrm{V}$ is lower than observed in the experimental data. This finding shows that the additional pressure—as expected from lattice QCD calculations at finite quark chemical potential and temperature—is generated by strong partonic interactions in the early phase of central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ ($\mathrm{P}\mathrm{b}+\mathrm{P}\mathrm{b}$) collisions.

Chiral doublet bands based on the $\pi g_{9/2}\otimes \nu h_{11/2}$ configuration that achieve degeneracy at spin $I=17$ in the odd-odd triaxial ${}^{104}\mathrm{R}\mathrm{h}$ nucleus have been observed. Experimental verification of the interpretation has been tested against specific fingerprints of chirality in the intrinsic system.

We have measured the spin structure functions $g_1$ and $g_2$ of ${}^3\mathrm{H}\mathrm{e}$ in a double-spin experiment by inclusively scattering polarized electrons at energies ranging from 0.862 to 5.058 GeV off a polarized ${}^3\mathrm{H}\mathrm{e}$ target at a $15.5°$ scattering angle. Excitation energies covered the resonance and the onset of the deep inelastic regions. We have determined for the first time the $Q^2$ evolution of ${\Gamma }_1(Q^2)={\int }_0^1{g}_1(x,Q^2)dx$, ${\Gamma }_2(Q^2)={\int }_0^1{g}_2(x,Q^2)dx$, and $d_2(Q^2)={\int }_0^1{x}^2[2g_1(x,Q^2)+3g_2(x,Q^2)]dx$ for the neutron in the range $0.1\le Q^2\le 0.9{\mathrm{G}\mathrm{e}\mathrm{V}}^2$ with good precision. ${\Gamma }_1(Q^2)$ displays a smooth variation from high to low $Q^2$. The Burkhardt-Cottingham sum rule holds within uncertainties and $d_2$ is nonzero over the measured range.