The level structure of ${}^{22}\mathrm{M}\mathrm{g}$ has been studied with high-sensitivity $\gamma$-ray spectroscopy techniques. A complete level scheme is derived incorporating all subthreshold states and all levels in the energy region relevant for novae burning. The excitation energy of the most important astrophysical resonance is measured with improved accuracy and found to differ from previous values. Combining the present result with a recent resonance energy measurement of this state leads to a derived ${}^{22}\mathrm{M}\mathrm{g}$ mass excess of $-400.5(13)\mathrm{k}\mathrm{e}\mathrm{V}$.

Unambiguous values of the spin and magnetic moment of ${}^{31}\mathrm{M}\mathrm{g}$ are obtained by combining the results of a hyperfine-structure measurement and a $\beta$-NMR measurement, both performed with an optically polarized ion beam. With a measured nuclear $g$ factor and spin $I=1/2$, the magnetic moment $\mu ({}^{31}\mathrm{M}\mathrm{g})=-0.88355(15){\mu }_N$ is deduced. A revised level scheme of ${}^{31}\mathrm{M}\mathrm{g}$ ($Z=12$, $N=19$) with ground state spin/parity $I^{\pi }=1/2^{+}$ is presented, revealing the coexistence of 1p-1h and 2p-2h intruder states below 500 keV. Advanced shell-model calculations and the Nilsson model suggest that the $I^{\pi }=1/2^{+}$ ground state is a strongly prolate deformed intruder state. This result plays a key role for the understanding of nuclear structure changes due to the disappearance of the $N=20$ shell gap in neutron-rich nuclei.

We compare elliptic flow evolution from ideal hydrodynamics and covariant parton transport theory, and show that, for conditions expected at RHIC, dissipation significantly reduces elliptic flow even for extreme parton cross sections and/or densities ${\sigma }_{gg}\times dN/d\eta (b=0)\sim 45\mathrm{m}\mathrm{b}\times 1000$. The difference between transport and hydrodynamic elliptic flow is established rather early during the evolution of the system, but the buildup of elliptic flow is insensitive to the choice of the initial (formation or thermalization) time in both models.

We investigate the transition from the nucleon-meson to the quark-gluon description of the strong interaction using the photon energy dependence of the $d(\gamma ,p)n$ differential cross section for photon energies above 0.5 GeV and center-of-mass proton angles between 30° and 150°. A possible signature for this transition is the onset of cross-section $s^{-11}$ scaling with the total energy squared, $s$, at some proton transverse momentum $P_T$. The results show that the scaling has been reached for proton transverse momentum above about $1.1\mathrm{G}\mathrm{e}\mathrm{V}/c$. This may indicate that the quark-gluon regime is reached above this momentum.

The ${}^3\mathrm{H}\mathrm{e}({}^4\mathrm{H}\mathrm{e},\gamma ){}^7\mathrm{B}\mathrm{e}$ reaction plays an important role in determining the high energy solar neutrino flux and in understanding the abundances of primordial ${}^7\mathrm{L}\mathrm{i}$. This Letter reports a new precision measurement of the cross sections of this direct capture reaction, determined by measuring the ensuing ${}^7\mathrm{B}\mathrm{e}$ activity in the region of $E_{\mathrm{c}.\mathrm{m}.}=420$ to 950 keV. Various recent theoretical fits to our data result in a consistent extrapolated value of $S_{34}(0)=0.53(2)(1)\mathrm{k}\mathrm{e}\mathrm{V}\mathrm{b}$.

We perform molecular dynamics simulations of screening by bound target electrons in low energy nuclear reactions. Quantum effects corresponding to the Pauli and Heisenberg principles are enforced by constraints. We show that the enhancement of the average cross section and of its variance is due to the perturbations induced by the electrons. This gives a correlation between the maximum amplitudes of the internuclear oscillational motion and the enhancement factor. It suggests that the chaotic behavior of the electronic motion affects the magnitude of the enhancement factor.

We calculate and resum a perturbative expansion of nuclear enhanced power corrections to the structure functions measured in deeply inelastic scattering of leptons on a nuclear target. Our results for the Bjorken $x$, $Q^2$ and $A$ dependence of nuclear shadowing in $F_2^A(x,Q^2)$ and the nuclear modification to $F_L^A(x,Q^2)$, obtained in terms of the QCD factorization approach, are consistent with the existing data. We demonstrate that the low $Q^2$ behavior of these data and the measured large longitudinal structure function point to a critical role for the power corrections when compared to other theoretical approaches.

The ${}^5\mathrm{H}$ system was produced in the ${}^3\mathrm{H}(t,p){}^5\mathrm{H}$ reaction studied with a 58 MeV tritium beam at small c.m. angles. High statistics data were used to reconstruct the energy and angular correlations between the ${}^5\mathrm{H}$ decay fragments. A broad structure in the ${}^5\mathrm{H}$ missing mass spectrum showing up above 2.5 MeV was identified as a mixture of the $3/2^{+}$ and $5/2^{+}$ states. The data also present evidence that the $1/2^{+}$ ground state of ${}^5\mathrm{H}$ is located at about 2 MeV.

Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions to those in $p+p$ at the same energy. The elliptic anisotropy $v_2$ is found to reach its maximum at $p_t\sim 3\mathrm{G}\mathrm{e}\mathrm{V}/c$, then decrease slowly and remain significant up to $p_t\approx 7–10\mathrm{G}\mathrm{e}\mathrm{V}/c$. Stronger suppression is found in the back-to-back high-$p_t$ particle correlations for particles emitted out of plane compared to those emitted in plane. The centrality dependence of $v_2$ at intermediate $p_t$ is compared to simple models based on jet quenching.

We report on a study of the transverse momentum dependence of nuclear modification factors $R_{d\mathrm{A}\mathrm{u}}$ for charged hadrons produced in $\mathrm{\text{deuteron}}+\mathrm{\text{gold}}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$, as a function of collision centrality and of the pseudorapidity ($\eta =0$, 1, 2.2, 3.2) of the produced hadrons. We find a significant and systematic decrease of $R_{d\mathrm{A}\mathrm{u}}$ with increasing rapidity. The midrapidity enhancement and the forward rapidity suppression are more pronounced in central collisions relative to peripheral collisions. These results are relevant to the study of the possible onset of gluon saturation at energies reached at BNL RHIC.

The phase structure of a two-fluid bosonic system is investigated. The proton-neutron interacting boson model possesses a rich phase structure involving three control parameters and multiple order parameters. The surfaces of quantum phase transition between spherical, axially symmetric deformed, and ${\mathrm{S}\mathrm{U}}_{\pi \nu }^{*}(3)$ triaxial phases are determined.

The ${}_{\Lambda }{}^{3,4}\mathrm{H}$ and ${}_{\Lambda }{}^4\mathrm{H}$ hypernuclear bound states have been observed for the first time in kaon electroproduction on ${}^{3,4}\mathrm{H}\mathrm{e}$ targets. The production cross sections have been determined at $Q^2=0.35{\mathrm{G}\mathrm{e}\mathrm{V}}^2$ and $W=1.91\mathrm{G}\mathrm{e}\mathrm{V}$. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the ${}^{3,4}\mathrm{H}\mathrm{e}(e,e^{\prime }{K}^{+}){}_{\Lambda }{}^{3,4}\mathrm{H}$ processes to the elementary cross section ${}^1\mathrm{H}(e,éK^{+})\Lambda$ on the free proton, measured during the same experiment.

Using effective field theory we derive inequalities for light nuclei in the Wigner symmetry limit. This is the limit where isospin and spin degrees of freedom can be interchanged. We prove that the energy of any three-nucleon state is bounded below by the average energy of the lowest two-nucleon and four-nucleon states. We show how this is modified by lowest-order terms breaking Wigner symmetry and prove general energy convexity results for $\mathrm{S}\mathrm{U}(N)$. We also discuss the inclusion of Wigner-symmetric three- and four-nucleon force terms.

In nucleus-nucleus collisions, high-$p_T$ partons interact with a dense medium, which possesses strong collective flow components. Here, we demonstrate that the resulting medium-induced gluon radiation does not depend solely on the energy density of the medium, but also on the collective flow. Both components can be disentangled by the measurement of particle production associated with high-$p_T$ trigger particles, jetlike correlations, and jets. In particular, we show that flow effects lead to a characteristic breaking of the rotational symmetry of the average jet energy and jet multiplicity distribution in the $\eta \times \varphi$ plane. We argue that data on the medium-induced broadening of jetlike particle correlations in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at the Relativistic Heavy-Ion Collider may provide evidence for a significant distortion of parton fragmentation due to the longitudinal collective flow.

We study the gauge field fluctuations in dense quark matter and determine the temperature of the induced first-order phase transition to the color-superconducting phase in weak coupling. We find that the local approximation of the coupling between the gauge potential and the order parameter, employed in the Ginzburg-Landau theory, has to be modified by restoring the full momentum dependence of the polarization function of gluons in the superconducting phase.

The asymptotic spectra and scaling properties of a mixed-symmetry Hamiltonian, which exhibits a second-order phase transition in its macroscopic limit, are examined for a system of $N$ interacting bosons. A second interacting boson-model Hamiltonian, which exhibits a first-order phase transition, is also considered. The latter shows many parallel characteristics and some notable differences, leaving it open to question as to the nature of its asymptotic critical-point properties.

Peripheral and semiperipheral collisions have been studied in the system ${}^{93}\mathrm{N}\mathrm{b}+{}^{93}\mathrm{N}\mathrm{b}$ at $38A\mathrm{M}\mathrm{e}\mathrm{V}$. The evaporative and midvelocity components of the light charged particle and intermediate mass fragment emissions have been carefully disentangled. In this way it was possible to obtain the average amount not only of charge and mass, but also of energy, pertaining to the midvelocity emission, as a function of an impact parameter estimator. This emission has a very important role in the overall balance of the reaction, as it accounts for a large fraction of the emitted mass and for more than half of the dissipated energy. As such, it may give precious clues on the microscopic mechanism of energy transport from the interaction zone toward the target and projectile remnants.

We have observed two $\gamma$-ray transitions in ${}_{\Lambda }{}^{16}\mathrm{O}$ from the 6.6 MeV excited $1_2^{-}$ state to both ground-state spin-doublet members ($1_1^{-},0^{-}$) by the ($K^{-},{\pi }^{-}\gamma$) reaction. We have obtained the ground-state doublet spacing to be $26.4\pm 1.6(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.5(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\mathrm{k}\mathrm{e}\mathrm{V}$ and the excitation energy of the $1_2^{-}$ state to be $6561.7\pm 1.1(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 1.7(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\mathrm{k}\mathrm{e}\mathrm{V}$. The ground-state doublet spacing provides a small but nonzero strength of the tensor interaction between a $\Lambda$ and a nucleon. This is the first experimental result on the $\Lambda N$ tensor interaction.

Following the heavy-ion fusion-evaporation reaction ${}^{32}\mathrm{S}+{}^{24}\mathrm{M}\mathrm{g}$ at 95 MeV beam energy the lifetimes of analogue states in the $T_z=\pm 1/2$ $A=51$ mirror nuclei ${}^{51}\mathrm{F}\mathrm{e}$ and ${}^{51}\mathrm{M}\mathrm{n}$ have been measured using the Cologne plunger device coupled to the GASP $\gamma$-ray spectrometer. The deduced $B(E2;27/2^{-}\to 23/2^{-})$ values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, ${\epsilon }_p$ and ${\epsilon }_n$, in the $fp$ shell. A comparison between the experimental results and several different large-scale shell-model calculations yields ${\epsilon }_p\sim 1.15e$ and ${\epsilon }_n\sim 0.80e$.

The $C2/M1$ ratio of the electromagnetic $N\to \Delta (1232)$ transition, which is important for determining the geometric shape of the nucleon, is shown to be related to the neutron elastic form factor ratio $G_C^n/G_M^n$. The proposed relation holds with good accuracy for the entire range of momentum transfers where data are available.