An $\alpha$-decay branch of $(1.4\pm 0.4)\times {10}^{-4}$ has been discovered in the decay of ${}^{109}\mathrm{I}$, which predominantly decays via proton emission. The measured $Q_{\alpha }$ value of $3918\pm 21\mathrm{keV}$ allows the indirect determination of the $Q$ value for proton emission from ${}^{105}\mathrm{Sb}$ of $356\pm 22\mathrm{keV}$, which is approximately of 130 keV more bound than previously reported. This result is relevant for the astrophysical rapid proton-capture process, which would terminate in the ${}^{105}\mathrm{Sn}(p,\gamma ){}^{106}\mathrm{Sb}(p,\gamma ){}^{107}\mathrm{Te}(\alpha \mathrm{\text{decay}}){}^{103}\mathrm{Sn}$ cycle at the densities expected in explosive hydrogen burning scenarios, unless unusually strong pairing effects result in a ${}^{103}\mathrm{Sn}(p,\gamma ){}^{104}\mathrm{Sb}(p,\gamma ){}^{105}\mathrm{Te}(\alpha \mathrm{\text{decay}}){}^{101}\mathrm{Sn})$ cycle.

The STAR collaboration at the BNL Relativistic Heavy-Ion Collider (RHIC) reports measurements of the inclusive yield of nonphotonic electrons, which arise dominantly from semileptonic decays of heavy flavor mesons, over a broad range of transverse momenta ($1.2<p_T<10\mathrm{GeV}/c$) in $p+p$, $d+\mathrm{Au}$, and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$. The nonphotonic electron yield exhibits an unexpectedly large suppression in central $\mathrm{Au}+\mathrm{Au}$ collisions at high $p_T$, suggesting substantial heavy-quark energy loss at RHIC. The centrality and $p_T$ dependences of the suppression provide constraints on theoretical models of suppression.

The inelastic scattering of neutrino off ${}^4\mathrm{He}$ is calculated microscopically at energies typical for core-collapse supernova environment. The calculation is carried out with the Argonne V18 nucleon-nucleon potential and the Urbana IX three-nucleon force. Full final state interaction is included via the Lorentz integral transform method. The contribution of axial meson exchange currents to the cross sections is taken into account from effective field theory of nucleons and pions to order $\mathcal{O}(Q^3)$.

A new accurate measurement of the tensor analyzing powers $T_{20}$, $T_{21}$, and $T_{22}$ in deuteron photodisintegration has been performed. Wide-aperture nonmagnetic detectors allowed broad kinematic coverage in a single set up: $E_{\gamma }=25$ to 600 MeV, and ${\theta }_p^{\mathrm{cm}}=24°$ to 48° and 70° to 102°. The new data provide a significant improvement over the few existing measurements. The angular dependency of the tensor asymmetries in deuteron photodisintegration is extracted for the first time.

One of the challenges in relating experimental measurements of the suppression in the number of $J/\psi$ mesons produced in heavy ion collisions to lattice QCD calculations is that whereas the lattice calculations treat $J/\psi$ mesons at rest, in a heavy ion collision a $c\overline{c}$ pair can have a significant velocity with respect to the hot fluid produced in the collision. The putative $J/\psi$ finds itself in a hot wind. We present the first rigorous nonperturbative calculation of the consequences of a wind velocity $v$ on the screening length $L_s$ for a heavy quark-antiquark pair in hot $\mathcal{N}=4$ supersymmetric QCD. We find $L_s(v,T)=f(v)[1-v^2{]}^{1/4}/\pi T$ with $f(v)$ only mildly dependent on $v$ and the wind direction. This $L_s(v,T)\sim L_s(0,T)/\sqrt{\gamma }$ velocity scaling, if realized in QCD, provides a significant additional source of $J/\psi$ suppression at transverse momenta which are high but within experimental reach.

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

We prove a general theorem on spectral convexity with respect to particle number for $2N$ degenerate components of fermions. The number of spatial dimensions is arbitrary, and the system may be uniform or constrained by an external potential. We assume only that the interactions are governed by an $\mathrm{SU}(2N)$-invariant two-body potential whose Fourier transform is negative definite. The convexity result implies that the ground state is in a $2N$-particle clustering phase. We discuss implications for light nuclei as well as asymmetric nuclear matter in neutron stars.

We compute the shear viscosity of weakly coupled $\mathcal{N}=4$ supersymmetric Yang-Mills theory. Our result for $\eta /s$, the viscosity to entropy-density ratio, is many times smaller than the corresponding weak-coupling result in QCD. This suggests that $\eta /s$ of QCD near the transition point is several times larger than the viscosity bound, $\eta /s\ge 1/4\pi$.

The first excited $2^{+}$ state of the unstable isotope ${}^{110}\mathrm{Sn}$ has been studied in safe Coulomb excitation at $2.82\mathrm{MeV}/u$ using the MINIBALL array at the REX-ISOLDE post accelerator at CERN. This is the first measurement of the reduced transition probability of this state using this method for a neutron deficient Sn isotope. The strength of the approach lies in the excellent peak-to-background ratio that is achieved. The extracted reduced transition probability, $B(E2:0^{+}\to 2^{+})=0.220\pm 0.022e^2{b}^2$, strengthens the observation of the evolution of the $B(E2)$ values of neutron deficient Sn isotopes that was observed recently in intermediate-energy Coulomb excitation of ${}^{108}\mathrm{Sn}$. It implies that the trend of these reduced transition probabilities in the even-even Sn isotopes is not symmetric with respect to the midshell mass number $A=116$ as ${}^{100}\mathrm{Sn}$ is approached.

The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with $0.3<p_T<9\mathrm{GeV}/c$ at midrapidity ($|y|<0.35$) from heavy-flavor (charm and bottom) decays in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$. The nuclear modification factor $R_{\mathrm{AA}}$ relative to $p+p$ collisions shows a strong suppression in central $\mathrm{Au}+\mathrm{Au}$ collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy $v_2$ with respect to the reaction plane is observed for $0.5<p_T<5\mathrm{GeV}/c$ indicating substantial heavy-flavor elliptic flow. Both $R_{\mathrm{AA}}$ and $v_2$ show a $p_T$ dependence different from those of neutral pions. A comparison to transport models which simultaneously describe $R_{\mathrm{AA}}(p_T)$ and $v_2(p_T)$ suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.

The dependence of transverse momentum spectra of neutral pions and $\eta$ mesons with $p_T<16\mathrm{GeV}/c$ and $p_T<12\mathrm{GeV}/c$, respectively, on the centrality of the collision has been measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) in $d+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The measured yields are compared to those in $p+p$ collisions at the same $\sqrt{s_{NN}}$ scaled by the number of underlying nucleon-nucleon collisions in $d+\mathrm{Au}$. At all centralities, the yield ratios show no suppression, in contrast to the strong suppression seen for central $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC. Only a weak $p_T$ and centrality dependence can be observed.

Clear evidence for symplectic symmetry in low-lying states of ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ is reported. Eigenstates of ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$, determined within the framework of the no-core shell model using the $J$-matrix inverse scattering potential with $A\le 16$ (JISP16) nucleon-nucleon ($NN$) realistic interaction, typically project at the 85%–90% level onto a few of the most deformed symplectic basis states that span only a small fraction of the full model space. The results are nearly independent of whether the bare or renormalized effective interactions are used in the analysis. The outcome confirms Elliott’s SU(3) model which underpins the symplectic scheme, and above all, points to the relevance of a symplectic no-core shell model that can reproduce experimental $B(E2)$ values without effective charges as well as deformed spatial modes associated with clustering phenomena in nuclei.

The four-body equations of Alt, Grassberger, and Sandhas are solved, for the first time, for proton-${}^3\mathrm{He}$ scattering including the Coulomb interaction between the three protons using the method of screening and renormalization as was done recently for proton-deuteron scattering. Various realistic two-nucleon potentials are used. Large Coulomb effects are seen on all observables. Comparison with data at different energies shows large deviations in the proton analyzing power but quite reasonable agreement in other observables. The effect of the nucleon-nucleon magnetic moment interaction and correlations between $p\mathrm{\text{−}}d$ and $p\mathrm{\text{−}}{}^3\mathrm{He}$ analyzing powers are studied.

Differential measurements of elliptic flow ($v_2$) for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ are used to test and validate predictions from perfect fluid hydrodynamics for scaling of $v_2$ with eccentricity, system size, and transverse kinetic energy (${\mathrm{KE}}_T$). For ${\mathrm{KE}}_T\equiv m_T-m$ up to $\sim 1\mathrm{GeV}$ the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of ${\mathrm{KE}}_T$ mesons and baryons scale separately. Quark number scaling reveals a universal scaling of $v_2$ for both mesons and baryons over the full ${\mathrm{KE}}_T$ range for $\mathrm{Au}+\mathrm{Au}$. For $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Cu}+\mathrm{Cu}$ the scaling is more pronounced in terms of ${\mathrm{KE}}_T$, rather than transverse momentum.

Ramsey’s method of separated oscillatory fields is applied to the excitation of the cyclotron motion of short-lived ions in a Penning trap to improve the precision of their measured mass values. The theoretical description of the extracted ion-cyclotron-resonance line shape is derived and its correctness demonstrated experimentally by measuring the mass of the short-lived ${}^{38}\mathrm{Ca}$ nuclide with an uncertainty of $1.1\times {10}^{-8}$ using the Penning trap mass spectrometer ISOLTRAP at CERN. The mass of the superallowed beta emitter ${}^{38}\mathrm{Ca}$ contributes for testing the theoretical corrections of the conserved-vector-current hypothesis of the electroweak interaction. It is shown that the Ramsey method applied to Penning trap mass measurements yields a statistical uncertainty similar to that obtained by the conventional technique but 10 times faster. Thus the technique is a new powerful tool for high-precision mass measurements.

The invariant mass spectra of $\varphi \to K^{+}{K}^{-}$ are measured in 12 GeV $p+A$ reactions in order to search for the in-medium modification of $\varphi$ mesons. The observed $K^{+}{K}^{-}$ spectra are well reproduced by the relativistic Breit-Wigner function with a combinatorial background shape in three $\beta \gamma$ regions between 1.0 and 3.5. The nuclear mass number dependence of the yields of the $K^{+}{K}^{-}$ decay channel is compared to the simultaneously measured $e^{+}{e}^{-}$ decay channel for carbon and copper targets. We parameterize the production yields as $\sigma (A)={\sigma }_0{A}^{\alpha }$ and obtain ${\alpha }_{\varphi \to K^{+}{K}^{-}}-{\alpha }_{\varphi \to e^{+}{e}^{-}}$ to be $0.14\pm 0.12$. Limits are obtained for the partial decay widths of the $\varphi$ mesons in nuclear matter.

A classical dynamical model that treats breakup stochastically is presented for low energy reactions of weakly bound nuclei. The three-dimensional model allows a consistent calculation of breakup, incomplete, and complete fusion cross sections. The model is assessed by comparing the breakup observables with continuum discretized coupled-channel quantum mechanical predictions, which are found to be in reasonable agreement. Through the model, it is demonstrated that the breakup probability of the projectile as a function of its distance from the target is of primary importance for understanding complete and incomplete fusion at energies near the Coulomb barrier.

Simple geometrical considerations show that the collision zone in high energy nuclear collisions may be divided into a central part (“core”), with high energy densities, and a peripheral part (“corona”), with smaller energy densities, more like in $pp$ or $pA$ collisions. We present calculations that allow us to separate these two contributions, and which show that the corona contribution is quite small (but not negligible) for central collisions, but gets increasingly important with decreasing centrality. We will discuss consequences concerning results obtained in heavy ion collisions at the BNL Relativistic Heavy Ion Collider and CERN Super Proton Synchrotron.

The energy splitting of the ${}^{229}\mathrm{Th}$ ground-state doublet is measured to be $7.6\pm 0.5\mathrm{eV}$, significantly greater than earlier measurements. Gamma rays produced following the alpha decay of ${}^{233}\mathrm{U}$ ($105\mu \mathrm{Ci}$) were counted in the NASA/electron beam ion trap x-ray microcalorimeter spectrometer with an experimental energy resolution of 26 eV (FWHM). A difference technique was applied to the gamma-ray decay of the 71.82 keV level that populates both members of the doublet. A positive correction amounting to 0.6 eV was made for the unobserved interband decay of the 29.19 keV state ($29.19\to 0\mathrm{keV}$).

We report on a study of the longitudinal to transverse cross section ratio, $R={\sigma }_L/{\sigma }_T$, at low values of $x$ and $Q^2$, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range $0.06<Q^2<2.8{\mathrm{GeV}}^2$. Even at the lowest values of $Q^2$, $R$ remains nearly constant and does not disappear with decreasing $Q^2$, as might be expected. We find a nearly identical behavior for hydrogen and deuterium.