We report new measurements of the parity-violating asymmetry $A_{\mathrm{PV}}$ in elastic scattering of 3 GeV electrons off hydrogen and ${}^4\mathrm{He}$ targets with $⟨{\theta }_{\mathrm{lab}}⟩\approx 6.0°$. The ${}^4\mathrm{He}$ result is $A_{\mathrm{PV}}=\mathbf{(}+6.40\pm 0.23(\mathrm{stat})\pm 0.12(\mathrm{syst})\mathbf{)}\times {10}^{-6}$. The hydrogen result is $A_{\mathrm{PV}}=\mathbf{(}-1.58\pm 0.12(\mathrm{stat})\pm 0.04(\mathrm{syst})\mathbf{)}\times {10}^{-6}$. These results significantly improve constraints on the electric and magnetic strange form factors $G_E^s$ and $G_M^s$. We extract $G_E^s=0.002\pm 0.014\pm 0.007$ at $⟨Q^2⟩=0.077{\mathrm{GeV}}^2$, and $G_E^s+0.09G_M^s=0.007\pm 0.011\pm 0.006$ at $⟨Q^2⟩=0.109{\mathrm{GeV}}^2$, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.

The first excited $0^{+}$ state in ${}^{12}\mathrm{C}$ (Hoyle state) has been predicted to be a dilute self-bound gas of bosonic $\alpha$ particles, similar to a Bose-Einstein condensate. To clarify this conjecture, precise electron scattering data on form factors of the ground state and the transition to the Hoyle state are compared with results of the fermionic molecular dynamics model, a microscopic $\alpha$-cluster model, and an $\alpha$-cluster model with reduced degrees of freedom (in the spirit of a Bose-Einstein condensed state). The data indicate clearly a dilute density with a large spatial extension of the Hoyle state. A closer inspection of the model calculations, which reproduce the experimental findings, reveals that the term Bose-Einstein condensation of three $\alpha$ particles must not be taken too literally.

We analyze the anti–de Sitter/conformal-field-theory dual geometry of an expanding boost-invariant plasma. We show that the requirement of nonsingularity of the dual geometry for leading and subasymptotic times predicts, without any further assumptions about gauge theory dynamics, hydrodynamic expansion of the plasma with viscosity coefficient exactly matching the one obtained earlier in the static case by Policastro, Son, and Starinets.

Scenarios with dropping vector meson masses, motivated by the work of Brown and Rho, have been strongly discussed after recent NA60 Collaboration data were presented. In this Letter they are investigated within a nonequilibrium field theoretical description that includes quantum mechanical memory. Dimuon yields are calculated by application of a model for the fireball, and strong modifications are found in the comparison to quasiequilibrium calculations, which assume instantaneous adjustment of all meson properties to the surrounding medium. In addition, results for the situation of very broad excitations are presented.

A new frontier of discrete-line $\gamma$-ray spectroscopy at ultrahigh spin has been opened in the rare-earth nuclei ${}^{157,158}\mathrm{Er}$. Four rotational structures, displaying high moments of inertia, have been identified, which extend up to spin $\sim 65\hslash$ and bypass the band-terminating states in these nuclei which occur at $\sim 45\hslash$. Cranked Nilsson-Strutinsky calculations suggest that these structures arise from well-deformed triaxial configurations that lie in a valley of favored shell energy which also includes the triaxial strongly deformed bands in ${}^{161–167}\mathrm{Lu}$.

We study $(3+1)\mathrm{D}$ kinetic (Boltzmann-Vlasov) equations for relativistic plasma particles in a one dimensionally expanding geometry motivated by ultrarelativistic heavy-ion collisions. We set up local equations in terms of Yang-Mills potentials and auxiliary fields that allow simulations of hard- (expanding-) loop dynamics on a lattice. We determine numerically the evolution of plasma instabilities in the linear (Abelian) regime and also derive their late-time behavior analytically, which is consistent with recent numerical results on the evolution of the so-called melting color-glass condensate. We also find a significant delay in the onset of growth of plasma instabilities which are triggered by small rapidity fluctuations, even when the initial state is highly anisotropic.

Inelastic scattering of ${}^{40}\mathrm{Ca}$ on ${}^{40}\mathrm{Ca}$ at $50\mathrm{MeV}/\mathrm{A}$ has been measured in coincidence with protons at the GANIL facility. The SPEG spectrometer was associated with 240 CsI(Tl) scintillators of the INDRA $4\pi$ array, allowing for the measurement of complete decay events. The missing energy method was applied to these events. For events with excitation energy between 42 and 55 MeV, a direct decay branch by three protons towards the low energy states of ${}^{37}\mathrm{Cl}$ gives the first evidence for a 3-phonon state built with giant resonances.

Radiative $\alpha$-particle capture into the first excited, $J^{\pi }=0^{+}$ state of ${}^{16}\mathrm{O}$ at 6.049 MeV excitation energy has rarely been discussed as contributing to the ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction cross section due to experimental difficulties in observing this transition. We report here measurements of this radiative capture in ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ for center-of-mass energies of $E=2.22\mathrm{MeV}$ to 5.42 MeV at the DRAGON recoil separator. To determine cross sections, the acceptance of the recoil separator has been simulated in GEANT as well as measured directly. The transition strength between resonances has been identified in $R$-matrix fits as resulting both from $E2$ contributions as well as $E1$ radiative capture. Details of the extrapolation of the total cross section to low energies are then discussed [$S_{6.0}(300)={25}_{-15}^{+16}\mathrm{keV}\mathrm{b}$] showing that this transition is likely the most important cascade contribution for ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$.

Theoretical calculations predict ${}^{270}\mathrm{Hs}$ ($Z=108$, $N=162$) to be a doubly magic deformed nucleus, decaying mainly by $\alpha$-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the ${}^{26}\mathrm{Mg}+{}^{248}\mathrm{Cm}$ reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide ${}^{270}\mathrm{Hs}$, which decays by $\alpha$-particle emission with $Q_{\alpha }=9.02\pm 0.03\mathrm{MeV}$ to ${}^{266}\mathrm{Sg}$ which undergoes spontaneous fission with a half-life of ${444}_{-148}^{+444}\mathrm{ms}$. A production cross section of about 3 pb was measured for ${}^{270}\mathrm{Hs}$. Thus, ${}^{270}\mathrm{Hs}$ is the first nucleus for which experimental nuclear decay properties have become available for comparison with theoretical predictions of the $N=162$ shell stability.

The $\beta$-decay $Q_{\mathrm{EC}}$ values of the superallowed beta emitters ${}^{26}\mathrm{Al}^m$, ${}^{42}\mathrm{Sc}$, and ${}^{46}\mathrm{V}$ have been measured with a Penning trap to a relative precision of better than $8\times {10}^{-9}$. Our result for ${}^{46}\mathrm{V}$, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based $Q_{\mathrm{EC}}$ value. However, our results for ${}^{26}\mathrm{Al}^m$ and ${}^{42}\mathrm{Sc}$, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two techniques, this result demonstrates that no significant shift in the deduced value of $V_{ud}$ should be anticipated.

We study $J/\psi$ production at RHIC and LHC energies with both initial production at energies reached and the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) with regeneration. We solve the coupled set of transport equations for the $J/\psi$ distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the $J/\psi$ momentum distribution while the elliptic flow is still dominated by initial production. At energies reached at the LHC energy, almost all the initially created $J/\psi s$ are dissociated in the medium and regeneration dominates the $J/\psi$ properties.

It is shown that at a large temperature and $E\to \infty$ the QCD collisional energy loss reads $dE/dx\sim \alpha (m_D^2)T^2$. Compared to previous approaches, which led to $d{E}^B/dx\sim {\alpha }^2{T}^2\ln (ET/m_D^2)$ similar to the Bethe-Bloch formula in QED, we take into account the running of the strong coupling. As one significant consequence, due to asymptotic freedom, $dE/dx$ becomes $E$ independent for large parton energies. Some implications with regard to heavy ion collisions are pointed out.

A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range $200<E_{\gamma }<800\mathrm{MeV}$. The experiment used a $4\pi$ detection system, a circularly polarized tagged photon beam and a frozen-spin target which provided longitudinally polarized deuterons. The contribution to the Gerasimov-Drell-Hearn sum rule for the deuteron determined from the data is $407\pm 20(\mathrm{stat})\pm 24(\mathrm{syst})\mu \mathrm{b}$ for $200<E_{\gamma }<800\mathrm{MeV}$.

The successes of the nuclear shell model in explaining the stability properties of magic nuclei are challenged by the observation of rotational bands for which the sequential filling of single-particle energy levels of the spherical shell model are not respected. This Letter proposes criteria for identifying the shell-model configurations appropriate for describing such bands of states.

We show that in collisions with neutron-rich heavy ions at energies around the production threshold $K^0$ and $K^{+}$ yields probe the isospin-dependent part of the nuclear equation of state at high baryon densities. In particular, we suggest the $K^0/K^{+}$ ratio as a promising observable. Results obtained in a covariant relativistic transport approach are presented for $\mathrm{Au}+\mathrm{Au}$ collisions at $0.8–1.8A\mathrm{GeV}$. The focus is put on the equation of state influence which goes beyond the collision-cascade picture. The isovector part of the in-medium interaction affects the kaon multiplicities via two mechanisms: (i) a symmetry potential effect, i.e., a larger neutron repulsion in $n$-rich systems, and (ii) a threshold effect, due to the change in the self-energies of the particles involved in inelastic processes. Genuine relativistic contributions are revealed that could allow one to directly “measure” the Lorentz structure of the effective isovector interaction.

Elliptic flow at BNL RHIC is computed event by event with NeXSPheRIO. We show that when symmetry of the particle distribution in relation to the reaction plane is assumed, as usually done in the experimental extraction of elliptic flow, there is a disagreement between the true and reconstructed elliptic flows (15%–30% for $\eta =0$, 30% for $p_{\perp }=0.5\mathrm{GeV}$). We suggest a possible way to take into account the asymmetry and get good agreement between these elliptic flows.

Theoretical studies of the inclusive electron-nucleus cross section at beam energies up to a few GeV show that, while the region of the quasielastic peak is understood at the quantitative level, the data in the $\Delta$ production region are sizably underestimated. We analyze the uncertainty associated with the description of the nucleon structure functions $W_1$ and $W_2$ and its impact on the nuclear cross section. The results of our study suggest that the failure to reproduce the data is to be mostly ascribed to the poor knowledge of the neutron structure functions at low $Q^2$.

The reaction ${}^{13}\mathrm{C}(\alpha ,n)$ is considered to be the main source of neutrons for the $s$ process in asymptotic giant branch stars. At low energies, the cross section is dominated by the $1/2^{+}$ 6.356 MeV subthreshold resonance in ${}^{17}\mathrm{O}$ whose contribution at stellar temperatures is uncertain by a factor of 10. In this work, we performed the most precise determination of the low-energy astrophysical $S$ factor using the indirect asymptotic normalization (ANC) technique. The $\alpha$-particle ANC for the subthreshold state has been measured using the sub-Coulomb $\alpha$-transfer reaction $({}^6\mathrm{Li},d)$. Using the determined ANC, we calculated $S(0)$, which turns out to be an order of magnitude smaller than in the nuclear astrophysics compilation of reaction rates.

Models of medium-induced radiative parton energy loss account for the strong suppression of high-$p_T$ hadron spectra in $\sqrt{s_{NN}}=200\mathrm{GeV}$ Au-Au collisions at BNL RHIC in terms of a single “jet quenching parameter” $\widehat{q}$. We observe that $\widehat{q}$ can be given a model-independent, nonperturbative, quantum field theoretic definition in terms of the short-distance behavior of a particular lightlike Wilson loop. We then use the anti–de Sitter/conformal-field-theory correspondence to obtain a strong-coupling calculation of $\widehat{q}$ in hot $\mathcal{N}=4$ supersymmetric QCD, finding ${\widehat{q}}_{\mathrm{SYM}}=26.69\sqrt{{\alpha }_{\mathrm{SYM}}{N}_c}{T}^3$ in the limit in which both $N_c$ and $4\pi {\alpha }_{\mathrm{SYM}}{N}_c$ are large. Thus, at strong coupling $\widehat{q}$ is not proportional to the entropy density $s$, or to some “number density of scatterers” since, unlike the number of degrees of freedom, $\widehat{q}$ does not grow like $N_c^2$.

A concentration of electric-dipole excitations below the particle threshold, which is frequently denoted as the pygmy dipole resonance, has been studied in the semimagic nucleus ${}^{140}\mathrm{Ce}$ in ($\alpha$, ${\alpha }^{\prime }\gamma$) experiments at $E_{\alpha }=136\mathrm{MeV}$. The technique of $\alpha \mathrm{\text{−}}\gamma$ coincidence experiments allows the separation of $E1$ excitations from states of other multipolarities in the same energy region and provides an excellent energy resolution to allow a detailed analysis for each state. The experimental results show that the PDR splits into two parts with different nuclear structure: one part which is excited in ($\alpha$, ${\alpha }^{\prime }\gamma$) as well as ($\gamma$, ${\gamma }^{\prime }$) experiments and one part which is excited only in ($\gamma$, ${\gamma }^{\prime }$).