The masses of six neutron-deficient rare holmium and thulium isotopes close to the proton drip line were determined with the SHIPTRAP Penning trap mass spectrometer. For the first time the masses of the proton-unbound isotopes ${}^{144,145}\mathrm{Ho}$ and ${}^{147,148}\mathrm{Tm}$ were directly measured. The proton separation energies were derived from the measured mass values and compared to predictions from mass formulas. The new values of the proton separation energies are used to determine the location of the proton drip line for holmium and thulium more accurately.

We evaluate the Poynting vector generated by a heavy quark moving through a thermal state of $\mathcal{N}=4$ gauge theory using the gauge-string duality. A significant diffusion wake is observed as well as a Mach cone. We discuss the ratio of the energy going into sound modes to the energy coming in from the wake.

We present predictions for the pseudorapidity density of charged particles produced in central Pb-Pb collisions at the LHC. Particle production in such collisions is calculated in the framework of $k_t$ factorization. The nuclear unintegrated gluon distributions at LHC energies are determined from numerical solutions of the Balitsky-Kovchegov equation including recently calculated running coupling corrections. The initial conditions for the evolution are fixed by fitting Relativistic Heavy Ion Collider data at collision energies $\sqrt{s_{\mathrm{NN}}}=130$ and 200 GeV per nucleon. We obtain $d{N}_{\mathrm{ch}}^{\mathrm{Pb}\mathrm{\text{−}}\mathrm{Pb}}/d\eta (\sqrt{s_{\mathrm{NN}}}=5.5\mathrm{TeV}){|}_{\eta =0}\approx 1290–1480$.

The photoproduction of vector mesons on various nuclei has been studied using the CLAS detector at Jefferson Laboratory. The vector mesons, $\rho$, $\omega$, and $\varphi$, are observed via their decay to $e^{+}{e}^{-}$, in order to reduce the effects of final-state interactions in the nucleus. Of particular interest are possible in-medium effects on the properties of the $\rho$ meson. The $\rho$ mass spectrum is extracted from the data on various nuclei, ${}^2\mathrm{H}$, C, Fe, and Ti. We observe no significant mass shift and some broadening consistent with expected collisional broadening for the $\rho$ meson.

A measurement of the production of ultracold neutrons from velocity-selected cold neutrons on gaseous and solid deuterium targets is reported. The expected energy dependence for two-particle collisions with well defined neutron and Maxwell-Boltzmann distributed molecular velocities is found for the gas target. The solid target data agree in shape with the phonon density-of-states curve and provide strong evidence for the phonon model including multiphonon excitations.

We report on the first measurement of the ${\beta }^{+}$ and orbital electron-capture decay rates of ${}^{140}\mathrm{Pr}$ nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike ${}^{140}\mathrm{Pr}^{58+}$ ions is about 50% larger than that of heliumlike ${}^{140}\mathrm{Pr}^{57+}$ ions. Moreover, ${}^{140}\mathrm{Pr}$ ions with one bound electron decay faster than neutral ${}^{140}\mathrm{Pr}^{0+}$ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.

The root-mean-square (rms) nuclear charge radius of ${}^8\mathrm{He}$, the most neutron-rich of all particle-stable nuclei, has been determined for the first time to be 1.93(3) fm. In addition, the rms charge radius of ${}^6\mathrm{He}$ was measured to be 2.068(11) fm, in excellent agreement with a previous result. The significant reduction in charge radius from ${}^6\mathrm{He}$ to ${}^8\mathrm{He}$ is an indication of the change in the correlations of the excess neutrons and is consistent with the ${}^8\mathrm{He}$ neutron halo structure. The experiment was based on laser spectroscopy of individual helium atoms cooled and confined in a magneto-optical trap. Charge radii were extracted from the measured isotope shifts with the help of precision atomic theory calculations.

We have measured the nuclear transparency of the $A(e,e^{\prime }{\pi }^{+})$ process in ${}^2\mathrm{H}$, ${}^{12}\mathrm{C}$, ${}^{27}\mathrm{Al}$, ${}^{63}\mathrm{Cu}$, and ${}^{197}\mathrm{Au}$ targets. These measurements were performed at the Jefferson Laboratory over a four momentum transfer squared range $Q^2=1.1$ to $4.7(\mathrm{GeV}/c{)}^2$. The nuclear transparency was extracted as the super-ratio of (${\sigma }_A/{\sigma }_H$) from data to a model of pion-electroproduction from nuclei without $\pi \mathrm{\text{−}}N$ final-state interactions. The $Q^2$ and atomic number dependence of the nuclear transparency both show deviations from traditional nuclear physics expectations and are consistent with calculations that include the quantum chromodynamical phenomenon of color transparency.

We discuss two models in which a softening of the equation of state takes place due to the appearance of new degrees of freedom. The first is a hadronic model in which the softening is due to chiral symmetry restoration. In the second model the softening is associated with the formation of clusters of quarks in the mixed phase. We show that in the first case the bulk modulus is mainly dependent on the density, while in the mixed-phase model the bulk modulus strongly depends on the temperature and it is not vanishing due to the presence of two conserved charges, the baryon and the isospin one.

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent $\mathrm{D}(\overrightarrow{e},e^{\prime }\gamma )X$ cross section measured at $Q^2=1.9{\mathrm{GeV}}^2$ and $x_B=0.36$. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

Density fluctuations resulting from spinodal decomposition in a nonequilibrium first-order chiral phase transition are explored. We show that such instabilities generate divergent fluctuations of conserved charges along the isothermal spinodal lines appearing in the coexistence region. Thus, divergent density fluctuations could be a signal not only for the critical end point but also for the first-order phase transition expected in strongly interacting matter. We also compute the mean-field critical exponent at the spinodal lines. Our analysis is performed in the mean-field approximation to the Nambu–Jona-Lasinio model formulated at finite temperature and density. However, our main conclusions are expected to be generic and model independent.

The calculation of transport properties of Fermi liquids, based on the formalism developed by Abrikosov and Khalatnikov, requires the knowledge of the probability of collisions between quasiparticles in the vicinity of the Fermi surface. We have carried out a study of the shear viscosity of pure neutron matter, whose value plays a pivotal role in determining the stability of rotating neutron stars, in which these processes are described using a state-of-the-art nucleon-nucleon potential. Medium modifications of the scattering cross section have been consistently taken into account through an effective interaction obtained from the matrix elements of the bare interaction between correlated states. Medium effects produce a large increase of the viscosity at densities $\rho \gtrsim 0.1{\mathrm{fm}}^{-3}$.

We report on the first determination of the nuclear ground-state spin of ${}^{33}\mathrm{Mg}$, $I=3/2$, and its magnetic moment, $\mu =-0.7456(5){\mu }_N$, by combining laser spectroscopy with nuclear magnetic resonance techniques. These values are inconsistent with an earlier suggested 1 particle-1 hole configuration and provide evidence for a 2 particle-2 hole intruder ground state with negative parity. The results are in agreement with an odd-neutron occupation of the $3/2[321]$ Nilsson orbital at a large prolate deformation. The discussion emphasizes the need of further theoretical and experimental investigation of the island of inversion, a region previously thought to be well understood.

Level densities of $J^{\pi }=2^{+}$ and $2^{-}$ states extracted from high-resolution studies of $E2$ and $M2$ giant resonances in ${}^{58}\mathrm{Ni}$ and ${}^{90}\mathrm{Zr}$ are used to test recent predictions of a possible parity dependence. The experimental results are compared to a combinatorial approach based on the Hartree-Fock-Bogoliubov model and to shell-model Monte Carlo calculations including both spin and parity projection. No parity dependence is observed experimentally, which is in agreement for ${}^{90}\mathrm{Zr}$ but in contrast with the model predictions for ${}^{58}\mathrm{Ni}$.

Differential cross sections for transitions of known weak strength were measured with the (${}^3\mathrm{He}$, $t$) reaction at 420 MeV on targets of ${}^{12}\mathrm{C}$, ${}^{13}\mathrm{C}$, ${}^{18}\mathrm{O}$, ${}^{26}\mathrm{Mg}$, ${}^{58}\mathrm{Ni}$, ${}^{60}\mathrm{Ni}$, ${}^{90}\mathrm{Zr}$, ${}^{118}\mathrm{Sn}$, ${}^{120}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$. Using these data, it is shown that the proportionalities between strengths and cross sections for this probe follow simple trends as a function of mass number. These trends can be used to confidently determine Gamow-Teller strength distributions in nuclei for which the proportionality cannot be calibrated via $\beta$-decay strengths. Although theoretical calculations in the distorted-wave Born approximation overestimate the data, they allow one to understand the main experimental features and to predict deviations from the simple trends observed in some of the transitions.

We derive an expression relating the transport parameter $\widehat{q}$ and the shear viscosity $\eta$ of a weakly coupled quark-gluon plasma. A deviation from this relation can be regarded as a quantitative measure of “strong coupling” of the medium. The ratio $T^3/\widehat{q}$, where $T$ is the temperature, is a more broadly valid measure of the coupling strength of the medium than $\eta /s$, where $s$ denotes the entropy density. Different estimates of $\widehat{q}$ derived from existing Relativistic Heavy Ion Collider data are shown to imply radically different structures of the produced matter.

New measurements of fusion cross sections at deep sub-barrier energies for the reactions ${}^{16}\mathrm{O}+{}^{204,208}\mathrm{Pb}$ show a steep but almost saturated logarithmic slope, unlike ${}^{64}\mathrm{Ni}$-induced reactions. Coupled channels calculations cannot simultaneously reproduce these new data and above-barrier cross-sections with the same Woods-Saxon nuclear potential. It is argued that this highlights an inadequacy of the coherent coupled channels approach. It is proposed that a new approach explicitly including gradual decoherence is needed to allow a consistent description of nuclear fusion.

The decay of extremely neutron-deficient ${}^{45}\mathrm{Fe}$ has been studied in detail by means of a novel type of a gaseous detector employing digital imaging to record tracks of charged particles. The two-proton radioactivity channel was clearly identified. For the first time, the angular and energy correlations between two protons emitted from the nuclear ground state were determined, indicating the genuine three-body character of this decay. The half-life of ${}^{45}\mathrm{Fe}$ was found to be $2.6\pm 0.2\mathrm{ms}$ and the observed $2p$ decay branching ratio is $70\pm 4\%$.

In order to study the nucleus-nucleus interaction in Pb-based cold fusion, we have measured excitation functions for quasielastic scattering of ${}^{48}\mathrm{Ti}$, ${}^{54}\mathrm{Cr}$, ${}^{56}\mathrm{Fe}$, ${}^{64}\mathrm{Ni}$, and ${}^{70}\mathrm{Zn}$ projectiles on a ${}^{208}\mathrm{Pb}$ target at backward angles. The barrier distributions were derived from the first derivative of measured quasielastic scattering cross sections relative to the Rutherford scattering cross section. The centroids of the barrier distributions show a deviation from several predicted barrier heights toward the low energy side. The shape of the barrier distributions is well reproduced by the results of a coupled-channel calculation taking account of the coupling effects of two phonon excitations of the quadrupole vibration for the projectiles and of the octupole vibration for the ${}^{208}\mathrm{Pb}$ target.

We have observed the two-proton radioactivity of the previously unknown ${}^{19}\mathrm{Mg}$ ground state by tracking the decay products in-flight. For the first time, the trajectories of the $2p$-decay products, ${}^{17}\mathrm{Ne}+p+p$, have been measured by using tracking microstrip detectors which allowed us to reconstruct the $2p$-decay vertices and fragment correlations. The half-life of ${}^{19}\mathrm{Mg}$ deduced from the measured vertex distribution is 4.0(15) ps in the system of ${}^{19}\mathrm{Mg}$. The $Q$ value of the $2p$ decay of the ${}^{19}\mathrm{Mg}$ ground state inferred from the measured $p-p-{}^{17}\mathrm{Ne}$ correlations is 0.75(5) MeV.