The relative effects of the variation of the fine structure constant $\alpha =e^2/\hslash c$ and the dimensionless strong interaction parameter $m_q/{\Lambda }_{\mathrm{QCD}}$ are enhanced by 5–6 orders of magnitude in a very narrow ultraviolet transition between the ground and the first excited states in the ${}^{229}\mathrm{Th}$ nucleus. It may be possible to investigate this transition with laser spectroscopy. Such an experiment would have the potential of improving the sensitivity to temporal variation of the fundamental constants by many orders of magnitude.

The $N=28$ shell closure has been investigated via the ${}^{46}\mathrm{Ar}(d,p){}^{47}\mathrm{Ar}$ transfer reaction in inverse kinematics. Energies and spectroscopic factors of the neutron $p_{3/2}$, $p_{1/2}$, and $f_{5/2}$ states in ${}^{47}\mathrm{Ar}$ were determined and compared to those of the ${}^{49}\mathrm{Ca}$ isotone. We deduced a reduction of the $N=28$ gap by 330(90) keV and spin-orbit weakenings of $\simeq 10(2)$ and 45(10)% for the $f$ and $p$ states, respectively. Such large variations for the $f$ and $p$ spin-orbit splittings could be accounted for by the proton-neutron tensor force and by the density dependence of the spin-orbit interaction, respectively. This contrasts with the picture of the spin-orbit interaction as a surface term only.

We study the low-energy behavior of QCD Green functions in the limit that the baryon chemical potential is much larger than the QCD scale parameter ${\Lambda }_{\mathrm{QCD}}$. We show that there is a systematic low-energy expansion in powers of $(\omega /m{)}^{1/3}$, where $\omega$ is the energy and $m$ is the screening scale. This expansion is valid even if the effective quark-gluon coupling $g$ is not small. The expansion is purely perturbative in the magnetic regime $|\overrightarrow{k}|\gg k_0$. If the external momenta and energies satisfy $|\overrightarrow{k}|\sim k_0$, planar, Abelian ladder diagrams involving the full quark propagator have to be resummed but the corresponding Dyson-Schwinger equations are closed.

We have identified two isomers in ${}^{254}\mathrm{No}$, built on two- and four-quasiparticle excitations, with quantum numbers $K^{\pi }=8^{-}$ and (${14}^{+}$), as well as a low-energy 2-quasiparticle $K^{\pi }=3^{+}$ state. The occurrence of isomers establishes that $K$ is a good quantum number and therefore that the nucleus has an axial prolate shape. The 2-quasiparticle states probe the energies of the proton levels that govern the stability of superheavy nuclei, test 2-quasiparticle energies from theory, and thereby check their predictions of magic gaps.

Two new $\alpha$ emitters ${}^{109}\mathrm{Xe}$ and ${}^{105}\mathrm{Te}$ were identified through the observation of the ${}^{109}\mathrm{Xe}\to {}^{105}\mathrm{Te}\to {}^{101}\mathrm{Sn}$ $\alpha$-decay chain. The ${}^{109}\mathrm{Xe}$ nuclei were produced in the fusion-evaporation reaction ${}^{54}\mathrm{Fe}({}^{58}\mathrm{Ni},3n){}^{109}\mathrm{Xe}$ and studied using the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility. Two transitions at $E_{\alpha }=4062\pm 7\mathrm{keV}$ and $E_{\alpha }=3918\pm 9\mathrm{keV}$ were interpreted as the $l=2$ and $l=0$ transitions from the $7/2^{+}$ ground state in ${}^{109}\mathrm{Xe}$ ($T_{1/2}=13\pm 2\mathrm{ms}$) to the $5/2^{+}$ ground state and a $7/2^{+}$ excited state, located at $150\pm 13\mathrm{keV}$ in ${}^{105}\mathrm{Te}$. The observation of the subsequent decay of ${}^{105}\mathrm{Te}$ marks the discovery of the lightest known $\alpha$-decaying nucleus. The measured transition energy $E_{\alpha }=4703\pm 5\mathrm{keV}$ and half-life $T_{1/2}=620\pm 70\mathrm{ns}$ were used to determine the reduced $\alpha$-decay width ${\delta }^2$. The ratio ${\delta }_{{}^{105}\mathrm{Te}}^2/{\delta }_{{}^{213}\mathrm{Po}}^2$ of $\sim 3$ indicates a superallowed character of the $\alpha$ emission from ${}^{105}\mathrm{Te}$.

Calculations using realistic mean-field methods suggest the existence of nuclear shapes with tetrahedral $T_d$ and/or octahedral $O_h$ symmetries sometimes at only a few hundreds of keV above the ground states in some rare earth nuclei around ${}^{156}\mathrm{Gd}$ and ${}^{160}\mathrm{Yb}$. The underlying single-particle spectra manifest exotic fourfold rather than Kramers’s twofold degeneracies. The associated shell gaps are very strong, leading to a new form of shape coexistence in many rare earth nuclei. We present possible experimental evidence of the new symmetries based on the published experimental results—although an unambiguous confirmation will require dedicated experiments.

We generalize the hybrid magnetofluid model of a charged fluid interacting with an electromagnetic field to the dynamics of a relativistic hot fluid interacting with a non-Abelian field. The fluid itself is endowed with a non-Abelian charge and the consequences of this generalization are worked out. Applications of this formalism to the quark gluon plasma are suggested.

The low-spin structure of ${}^{93}\mathrm{Nb}$ has been studied using the $(n,n^{\prime }\gamma )$ reaction at neutron energies ranging from 1.5 to 3 MeV and the ${}^{94}\mathrm{Zr}(p,2n\gamma ){}^{93}\mathrm{Nb}$ reaction at bombarding energies from 11.5 to 19 MeV. States at 1779.7 and 1840.6 keV, respectively, are proposed as mixed-symmetry states associated with the $\pi 2p_{1/2}^{-1}\otimes (2_{1,\mathrm{MS}}^{+},{}^{94}\mathrm{Mo})$ coupling. These assignments are derived from the observed $M1$ and $E2$ transition strengths to the $2p_{1/2}^{-1}\otimes (2_1^{+},{}^{94}\mathrm{Mo})$ symmetric one-phonon states, energy systematics, spins and parities, and comparison with shell model calculations.

We study the effects of jet quenching on the hydrodynamical evolution of the quark-gluon plasma (QGP) fluid created in a heavy-ion collision. In jet quenching, a hard QCD parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to suppressed production of high-$p_T$ hadrons. Assuming that the deposited energy quickly thermalizes, we simulate the subsequent hydrodynamic evolution of the QGP fluid. For partons moving at supersonic speed, $v_p>c_s$, and sufficiently large energy loss, a shock wave forms leading to conical flow. The PHENIX Collaboration recently suggested that observed structures in the azimuthal angle distribution might be caused by conical flow. We show here that, for phenomenologically acceptable values of parton energy loss, conical flow effects are too weak to explain these structures.

Asymmetric resonances in elastic $n+{}^{19}\mathrm{C}$ scattering are attributed to Efimov states of such neutron-rich nuclei, that is, three-body bound states of the $n+n+{}^{18}\mathrm{C}$ system when none of the pairs is bound or some of them are only weakly bound. By fitting to the general resonance shape described by Fano, we extract the resonance position, width, and the “Fano profile index.” While Efimov states have been discussed extensively in many areas of physics, there is only one very recent experimental observation in trimers of cesium atoms. The conjunction that we present of the Efimov and Fano phenomena may lead to experimental realization in nuclei.

Lifetimes of prolate intruder states in ${}^{186}\mathrm{Pb}$ and oblate intruder states in ${}^{194}\mathrm{Po}$ have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in ${}^{188}\mathrm{Pb}$ up to the $8^{+}$ state were carried out using the recoil-gating method. The $B(E2)$ values have been deduced from which deformation parameters $|{\beta }_2|=0.29(5)$ and $|{\beta }_2|=0.17(3)$ for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes.

A new experimental approach to the famous problem of the anomalously slow Gamow-Teller (GT) transitions in the $\beta$ decay of the $A=14$ multiplet is presented. The GT strength distributions to excited states in ${}^{14}\mathrm{C}$ and ${}^{14}\mathrm{O}$ were studied in high-resolution $(d,{}^2\mathrm{He})$ and $({}^3\mathrm{He},t)$ charge-exchange reactions on ${}^{14}\mathrm{N}$. No-core shell-model calculations capable of reproducing the suppression of the $\beta$ decays predict a selective excitation of $J^{\pi }=2^{+}$ states. The experimental confirmation represents a validation of the assumptions about the underlying structure of the ${}^{14}\mathrm{N}$ ground state wave function. However, the fragmentation of the GT strength over three $2^{+}$ final states remains a fundamental issue not explained by the present no-core shell model using a $6\hslash \omega$ model space, suggesting possibly the need to include cluster structure in these light nuclei in a consistent way.

Recent measurements of preequilibrium neutron and proton transverse emission from ${}^{112,124}\mathrm{Sn}+{}^{112,124}\mathrm{Sn}$ reactions at $50\mathrm{MeV}/A$ have been completed at the National Superconducting Cyclotron Laboratory. Free nucleon transverse emission ratios are compared to those of $A=3$ mirror nuclei. Comparisons are made to Boltzmann-Uehling-Uhlenbeck (BUU) transport calculations and conclusions concerning the density dependence of the asymmetry term of the nuclear equation of state at subnuclear densities are made. Comparison to BUU model predictions indicate a density dependence of the asymmetry energy that is closer to a form in which the asymmetry energy increases as the square root of the density for the density region studied. A coalescent-invariant analysis is introduced as a means of reducing suggested difficulties with cluster emission in total nucleon emission.

Azimuthal correlations of jet-induced high-$p_T$ charged hadron pairs are studied at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The distribution of jet-associated partner hadrons ($1.0<p_T<2.5\mathrm{GeV}/c$) per trigger hadron ($2.5<p_T<4.0\mathrm{GeV}/c$) is found to vary with collision centrality, in both shape and yield, indicating a significant effect of the nuclear collision medium on the jet fragmentation process.

The production of pions and protons in the $p_T$ range between 10 and $20\mathrm{GeV}/c$ for $\mathrm{Pb}+\mathrm{Pb}$ collisions at CERN LHC is studied in the recombination model. It is shown that the dominant mechanism for hadronization is the recombination of shower partons from neighboring jets when the jet density is high. Protons are more copiously produced than pions in that $p_T$ range because the coalescing partons can have lower momentum fractions, but no thermal partons are involved. The proton-to-pion ratio can be as high as 20. When such high $p_T$ hadrons are used as trigger particles, there will not be any associated particles that are not in the background.

We report on measurements of directed flow as a function of pseudorapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at energies of $\sqrt{s_{NN}}=19.6$, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the BNL Relativistic Heavy Ion Collider. These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density.

The $\gamma$ decay of the giant dipole resonance (GDR) in the ${}^{132}\mathrm{Ce}$ compound nucleus with temperature up to $\approx 4\mathrm{MeV}$ has been measured, using the reaction ${}^{64}\mathrm{Ni}+{}^{68}\mathrm{Zn}$ at $E_{\mathrm{beam}}=300$, 400, and 500 MeV. The $\gamma$ and charged particles measured in coincidence with recoils are consistent with a fully equilibrated compound nucleus emission. The GDR width, obtained with the statistical model analysis, is found to increase almost linearly with temperature. This increase is rather well reproduced within a model including thermal shape fluctuations and the lifetime of the compound nucleus.

An exclusive measurement has been made of the Coulomb dissociation of the two-neutron halo nucleus ${}^{11}\mathrm{Li}$ at $70\mathrm{MeV}/\mathrm{nucleon}$ at RIKEN. Strong low-energy (soft) $E1$ excitation is observed, peaked at about $E_{\mathrm{x}}=0.6\mathrm{MeV}$ with $B(E1)=1.42(18){\mathrm{e}}^2{\mathrm{fm}}^2$ for $E_{\mathrm{rel}}\le 3\mathrm{MeV}$, which was largely missed in previous measurements. This excitation represents the strongest $E1$ transition ever observed at such low excitation energies. The spectrum is reproduced well by a three-body model with a strong two-neutron correlation, which is further supported by the $E1$ non-energy-weighted cluster sum rule.

The strength of the $E_{\mathrm{c}.\mathrm{m}.}=184\mathrm{keV}$ resonance in the ${}^{26g}\mathrm{Al}(p,\gamma ){}^{27}\mathrm{Si}$ reaction has been measured in inverse kinematics using the DRAGON recoil separator at TRIUMF’s ISAC facility. We measure a value of $\omega \gamma =35\pm 7\mu \mathrm{eV}$ and a resonance energy of $E_{\mathrm{c}.\mathrm{m}.}=184\pm 1\mathrm{keV}$, consistent with $p$-wave proton capture into the 7652(3) keV state in ${}^{27}\mathrm{Si}$, and discuss the implications of these values for ${}^{26g}\mathrm{Al}$ nucleosynthesis in typical oxygen-neon white-dwarf novae.

We argue that an expanding quark-gluon plasma has an anomalous viscosity, which arises from interactions with dynamically generated color fields. We derive an expression for the anomalous viscosity in the turbulent plasma domain and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma is near equilibrium. The anomalous viscosity dominates over the collisional viscosity for weak coupling and not too late times. This effect may provide an explanation for the apparent “nearly perfect” liquidity of the matter produced in nuclear collisions at the Relativistic Heavy Ion Collider without the assumption that it is a strongly coupled state.