I use the space-time distribution of energy and momentum deposited by a fast parton traversing a perturbative quark-gluon plasma as a source term for the linearized hydrodynamical equations of the medium. A method of solution for the medium response is presented in detail. Numerical results are given for different values of the shear viscosity to entropy density ratio, $\eta /s$, and speed of sound, $c_s$. Furthermore, I investigate the relevance of finite source structure by expanding the source term up to first order in gradients of a δ function centered at the fast parton and comparing the resulting dynamics to that obtained with the full source. It is found that, for the source term used here, the medium response is sensitive to the finite source structure up to distances of several femtometers from the source parton.

In view of recent data from the Thomas Jefferson National Accelerator Facility (JLab) on inclusive electron scattering off nuclei at high momentum transfer $(Q^2\gtrsim 1\hspace{0.5em}{\mathrm{GeV}}^2)$ and their current analysis, it is shown that, if the scaling variable is properly chosen, the analysis in terms of scaling functions can provide useful information on short-range correlations (SRC). This is demonstrated by introducing a new relativistic scaling variable that incorporates the momentum dependence of the excitation energy of the $(A-1)$ system, with the resulting scaling function being closely related to the longitudinal momentum distributions.

We present the first calculations of the electromagnetic form factors of ${}^3\mathrm{He}$ and ${}^3\mathrm{H}$ within the framework of the Covariant Spectator Theory (CST). This first exploratory study concentrates on the sensitivity of the form factors to the strength of the scalar meson-nucleon off-shell coupling, known from previous studies to have a strong influence on the three-body binding energy. Results presented here were obtained using the complete impulse approximation (CIA), which includes contributions of relativistic origin that appear as two-body corrections in a nonrelativistic framework, such as “Z-graphs,” but omits other two and three-body currents. We compare our results to nonrelativistic calculations augmented by relativistic corrections of $\mathcal{O}(v/c){}^2$.

The generalized deformed ${\mathrm{su}}_q(2)$ model is applied to 79 superdeformed bands in the region $A~190$. The transition energies and the moments of inertia are calculated within the model and their validity is investigated by comparing them with the experimental data. Both the standard ${\mathrm{su}}_q(2)$ and the generalized one fail to account for the uprising and the downturn of the dynamic moments of inertia. Both models, however, show remarkable agreement with the available experimental data at low angular frequancy ($\hslash \omega ⩽0.25$ MeV).

Relativistic Heavy Ion Collider experiments exhibit correlations peaked in relative azimuthal angle and extended in rapidity. Called the ridge, this peak occurs both with and without a jet trigger. We argue that the untriggered ridge arises when particles formed by flux tubes in an early Glasma stage later manifest transverse flow. Combining a blast wave model of flow fixed by single-particle spectra with a simple description of the Glasma, we find excellent agreement with current data.

The relativistic proton-neutron quasiparticle random phase approximation ($\mathit{pn}$-RQRPA) is applied in the calculation of total muon capture rates on a large set of nuclei from ${}^{12}\mathrm{C}$ to ${}^{244}\mathrm{Pu}$, for which experimental values are available. The microscopic theoretical framework is based on the relativistic Hartree-Bogoliubov (RHB) model for the nuclear ground state, and transitions to excited states are calculated using the $\mathit{pn}$-RQRPA. The calculation is fully consistent, i.e., the same interactions are used both in the RHB equations that determine the quasiparticle basis, and in the matrix equations of the $\mathit{pn}$-RQRPA. The calculated capture rates are sensitive to the in-medium quenching of the axial-vector coupling constant. By reducing this constant from its free-nucleon value $g_A=1.262$ by 10% for all multipole transitions, the calculation reproduces the experimental muon capture rates to better than 10% accuracy.

We calculate the relativistic entrainment matrix $Y_{\mathit{ik}}$ at zero temperature for a nucleon-hyperon mixture composed of neutrons, protons, and Λ and ${\Sigma }^{-}$ hyperons, as well as electrons and muons. This matrix is analogous to the entrainment matrix (also termed mass-density matrix or Andreev-Bashkin matrix) of nonrelativistic theory. It is an important ingredient for modeling the pulsations of massive neutron stars with superfluid nucleon-hyperon cores. The calculation is done in the frame of the relativistic Landau Fermi-liquid theory generalized to the case of superfluid mixtures; the matrix $Y_{\mathit{ik}}$ is expressed through the Landau parameters of nucleon-hyperon matter. The results are illustrated with a particular example of the $\sigma \text{−}\omega \text{−}\rho$ mean-field model with scalar self-interactions. Using this model, we calculate the matrix $Y_{\mathit{ik}}$ and the Landau parameters. We also analyze the stability of the ground state of nucleon-hyperon matter with respect to small perturbations.

We calculated the equation of state of neutron matter at zero temperature by means of the auxiliary field diffusion Monte Carlo (AFDMC) method combined with a fixed-phase approximation. The calculation of the energy was carried out by simulating up to 114 neutrons in a periodic box. Special attention was given to reducing finite-size effects at the energy evaluation by adding to the interaction the effect due to the truncation of the simulation box, and by performing several simulations using different numbers of neutrons. The finite-size effects due to kinetic energy were also checked by employing the twist-averaged boundary conditions. We considered a realistic nuclear Hamiltonian containing modern two- and three-body interactions of the Argonne and Urbana family. The equation of state can be used to compare and calibrate other many-body calculations and to predict properties of neutron stars.

We study the role of configuration mixing in the heavier even-even isotopes of argon. We begin by limiting the configurations of the even-even Ar isotopes to $(d_{3/2}^2){}_{\pi }\hspace{0.5em}(f_{7/2}^n){}_{\nu }$. There, due to the particular location in this shell-model space of ${}^{40}\mathrm{Ar}$ and ${}^{44}\mathrm{Ar}$, we find that the spectra, $B(E2)$'s, and magnetic moments of these two nuclei are identical. Any deviation from this equality is direct evidence of configuration mixing. In a larger shell-model space there are significant differences between these two nuclei, with ${}^{44}\mathrm{Ar}$ being more collective. We also consider other even-even isotopes of argon and study how their nuclear structure effects evolve with N. We compare in the full $0\hslash \hspace{0.5em}\omega$ space $(\mathit{sd}){}_{\pi }\hspace{0.5em}(\mathit{fp}){}_{\nu }$ the results of calculations with the WBT interaction and with the newer SDPF, denoted SDPF-U, interaction.

Point-form relativistic quantum mechanics is used to derive an expression for the electromagnetic form factor of a pseudoscalar meson for spacelike momentum transfers. The elastic scattering of an electron by a confined quark-antiquark pair is treated as a relativistic two-channel problem for the $q\overline{q}e$ and $q\overline{q}e\gamma$ states. With the approximation that the total velocity of the $q\overline{q}e$ system is conserved at (electromagnetic) interaction vertices this simplifies to an eigenvalue problem for a Bakamjian-Thomas type mass operator. After elimination of the $q\overline{q}e\gamma$ channel the electromagnetic meson current and form factor can be directly read off from the one-photon-exchange optical potential. By choosing the invariant mass of the electron-meson system large enough, cluster separability violations become negligible. An equivalence with the usual front-form expression, resulting from a spectator current in the $q^{+}=0$ reference frame, is established. The generalization of this multichannel approach to electroweak form factors for an arbitrary bound few-body system is quite obvious. By an appropriate extension of the Hilbert space this approach is also able to accommodate exchange-current effects.

Localized single-particle potentials for all octet baryons, $N$, $\Lambda$, $\Sigma$, and $\Xi$, in finite nuclei, ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, ${}^{28}\mathrm{Si}$, ${}^{40}\mathrm{Ca}$, ${}^{56}\mathrm{Fe}$, and ${}^{90}\mathrm{Zr}$, are calculated using the quark-model baryon-baryon interactions. $G$ matrices evaluated in symmetric nuclear matter in the lowest order Brueckner theory (LOBT) are applied to finite nuclei in local density approximation. Nonlocal potentials are localized by a zero-momentum Wigner transformation. Empirical single-particle properties of the nucleon and the $\Lambda$ hyperon in a nuclear medium have been known to be explained semiquantitatively in the LOBT framework. Attention is focused in the present consideration on predictions for the $\Sigma$ and $\Xi$ hyperons. The unified description for the octet baryon-baryon interactions by the ${\mathrm{SU}}_6$ quark model enables us to obtain less ambiguous extrapolation to the $S=-1$ and $S=-2$ sectors based on the knowledge in the $\mathit{NN}$ sector than other potential models. The $\Sigma$ mean field is shown to be weakly attractive at the surface, but turns out to be repulsive inside, which is consistent with the experimental evidence. The $\Xi$ hyperon s.p. potential is also attractive at the nuclear surface region, and inside it fluctuates around zero. Hence $\Xi$ hypernuclear bound states are unlikely. We also evaluate energy shifts of the ${\Sigma }^{-}$ and ${\Xi }^{-}$ atomic levels in ${}^{28}\mathrm{Si}$ and ${}^{56}\mathrm{Fe}$, using the calculated s.p. potentials.

Proton inelastic scattering on the neutron-rich nucleus ${}^{32}\mathrm{Mg}$ has been studied at 46.5 MeV/nucleon in inverse kinematics. Populated states were identified by measuring de-excitation $\gamma$ rays, in which five new states were found by $\gamma \text{−}\gamma$ coincidence analyses. By analyzing the angular differential cross sections via coupled-channel calculations, their spins and parities were constrained and the amplitudes for each transition were extracted. The spin and parity of the 2321-keV state was assigned as $4_1^{+}$. The ratio between the energies of the $2_1^{+}$ and $4_1^{+}$ states indicates that ${}^{32}\mathrm{Mg}$ is a transitional nucleus rather than an axially deformed rigid rotor. The collectivities in the nucleus ${}^{32}\mathrm{Mg}$ with $N=20$ are discussed based on the results obtained in the present experiment.

$\beta$ decay of the ${}^{61}\mathrm{Cr}{}_{37}$ ground state has been studied. A new half-life of $233\pm 11$ ms has been deduced, and seven delayed $\gamma$ rays have been assigned to the daughter ${}^{61}\mathrm{Mn}{}_{36}$. The low-energy level structure of ${}^{61}\mathrm{Mn}{}_{36}$ is similar to that of the less neutron-rich ${}^{57,59}\mathrm{Mn}$ nuclei. The odd-$A_{25}$Mn isotopes follow the systematic trend in the yrast states of the even-even, $Z+1$ ${}_{26}$Fe isotopes, and not that of the $Z-1$ ${}_{24}$Cr isotopes, where a possible onset of collectivity has been suggested to occur already at $N=36$.

The energy of the degenerate doublet $(3^{+}/2,5^{+}/2)$ of ${}_{\Lambda }^9\mathrm{Be}$, treating it as a partially nine-body system in the $\Lambda \alpha \alpha$ cluster model, has been calculated in the variational Monte Carlo framework. A simplified treatment, with the central two-body Urbana type $\Lambda N$ and the three-body dispersive and two-pion exchange $\Lambda \mathit{NN}$ forces along with the central two- and three-body correlations, is found to be adequate in explaining the energy of observed $\gamma$-ray transition from the excited degenerate doublet to the ground state. The hypernucleus ${}_{\Lambda }^9\mathrm{Be}$ is highly deformed and has an oblate shape in the excited state. The results of the present work are consistent with the earlier three-body cluster model analyzes of ${}_{\Lambda }^9\mathrm{Be}$.

The internal surrogate ratio method allows for the determination of an unknown cross section, such as $(n,\gamma )$, relative to a better-known cross section, such as $(n,f)$, by measuring the relative exit-channel probabilities of a surrogate reaction that proceeds through the same compound nucleus. The validity of the internal surrogate ratio method is tested by comparing the relative $\gamma$ and fission exit-channel probabilities of a ${}^{236}\mathrm{U}{}^{*}$ compound nucleus, formed in the ${}^{235}\mathrm{U}(d,p)$ reaction, to the known ${}^{235}\mathrm{U}(n,\gamma )$ and $(n,f)$ cross sections. A model-independent method for measuring the $\gamma$-channel yield is presented and used.

The fully microscopic $p$-nucleus optical potential has been calculated in the framework of the first order Brueckner theory employing Urbana V14, soft-core internucleon interaction along with the relativistic mean field densities both for protons and neutrons. It is observed that the volume integral per nucleon, of the real part of the spin-orbit interaction calculated for Zr ($A=76\text{−}110$) and Sn ($A=96\text{−}136$) isotopes, decreases with the increase in neutron number. The present optical model calculation satisfactorily reproduces the experimental (where available) cross sections and analyzing power. Further the magnitude of the first maximum (minimum) in the calculated analyzing power decreases (increases) with the addition of neutrons both for Zr and Sn isotopes reflecting the weakening of the spin-orbit interaction.

In this article we perform systematic calculations on low-lying states of 33 nuclei with $A=202\text{−}212$, using the nucleon pair approximation of the shell model. We use a phenomenological shell-model Hamiltonian that includes single-particle energies, monopole and quadrupole pairing interactions, and quadrupole-quadrupole interactions. The building blocks of our model space include one $J=4$ valence neutron pair, and one $J=4,6,8$ valence proton pair, in addition to the usual $S$ and $D$ pairs. We calculate binding energies, excitation energies, electric quadrupole and magnetic dipole moments of low-lying states, and $E2$ transition rates between low-lying states. Our calculated results are reasonably consistent with available experimental data. The calculated quadrupole moments and magnetic moments, many of which have not yet been measured for these nuclei, are useful for future experimental measurements.

The vacuum fluctuation (VF) effects on asymmetric nuclear matter are investigated. Masses of nucleons and mesons are modified in the nuclear medium by calculating the loop-diagram corrections and the density dependence of hadron masses is obtained. The relativistic Lagrangian density with the isovector scalar δ meson is used to calculate the nuclear equation of state (EOS) in the framework of the relativistic mean-field approach, and the effects of the in-medium hadron masses on the properties of neutron stars are finally studied. With the inclusion of the VF corrections, the nuclear EOS becomes softer and the neutron star masses are reduced.

The high spin states of neutron-rich ${}^{106,107}\mathrm{Tc}$ nuclei have been reinvestigated by observing prompt $\gamma$ rays from the spontaneous fission of ${}^{252}\mathrm{Cf}$. In ${}^{106}\mathrm{Tc}$, a previously known collective band is expanded, and a new collective band is identified. In ${}^{107}\mathrm{Tc}$, a collective band based on the $\pi 5/2^{-}[303]$ orbital is confirmed and extended. Inconsistencies in the configuration assignments for positive parity bands in ${}^{105,107}\mathrm{Tc}$ in the previous reports are clarified. The spins and parities as well as the configurations for the two bands in ${}^{106}\mathrm{Tc}$ are assigned according to the angular momentum alignments and $g$-factor calculations. Other characteristics for the observed bands are discussed.

The breakout reaction ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ from the hot CNO cycle is critical to understanding explosive astrophysical phenomena such as x-ray bursts. In spite of considerable past experimental effort via indirect methods, this reaction rate remained mostly uncertain until our recent measurement [Phys. Rev. Lett. 98, 242503 (2007)] of the eluding $\alpha$-decay branching ratios of the near-threshold states in ${}^{19}\mathrm{Ne}$, particularly the critical level at 4.03 MeV. In this paper, we present more details of and deeper insights into the measurement and the uncertainties of the experimental results. The $\alpha$-unbound states in ${}^{19}\mathrm{Ne}$ were populated via the reaction ${}^{19}\mathrm{F}({}^3\mathrm{He},t)$, and the $\alpha$-decay branch was observed from $t\text{−}\alpha$ coincidences using a low-energy particle detection array and the TWINSOL facility at the University of Notre Dame. In particular, the measured branching ratio of the 4.03-MeV state is $2.9\pm 2.1\times {10}^{-4}$. In combination with previous measurements of the lifetimes of these states, a new experimental reaction rate of ${}^{15}\mathrm{O}(\alpha ,\gamma ){}^{19}\mathrm{Ne}$ is proposed and discussed in the astrophysical scenario. Further experimental investigations are necessary to reduce the remaining uncertainties.