Production and equilibration of quark-gluon plasma are studied within the color flux-tube model, at the Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. Non-Abelian relativistic transport equations for quarks, antiquarks, and gluons, are solved in the extended phase space which includes coordinates, momenta, and color. Before the chromoelectric field is formed, hard and semihard partons are produced via minijets which provide the initial conditions necessary to solve the transport equations. The model predicts that in spite of the vast difference between the RHIC and LHC incident energies, once the local equilibrium is reached, the energy densities, the number densities, and the temperatures at the two machines may not be very different from each other. The minijet input significantly alters the evolution of the deconfined matter, unless the color field is too strong. For the input parameters used here the equilibration time is estimated to be $\sim 1\hspace{0.5em}\mathrm{fm}$ at RHIC and $\sim 0.5\hspace{0.5em}\mathrm{fm}$ at LHC, measured from the instant when the two colliding nuclei have just passed through each other. The temperature at equilibration is found to be $\sim 250\hspace{0.5em}\mathrm{MeV}$ at RHIC and $\sim 300\hspace{0.5em}\mathrm{MeV}$ at LHC.

Hot hypernuclear matter is investigated in an explicit SU(3) quark model based on a mean-field description of nonoverlapping baryon bags bound by the self-consistent exchange of scalar $\sigma ,\zeta$ and vector $\omega ,\phi$ mesons. The $\sigma ,\omega$ mean fields are assumed to couple to the $u,d$ quarks while the $\zeta ,\phi$ mean fields are coupled to the s quark. The coupling constants of the mean fields with the quarks are assumed to satisfy SU(6) symmetry. The calculations take into account the medium dependence of the bag parameter on the scalar fields $\sigma ,\zeta .$ We consider only the octet baryons $N,\Lambda ,\Sigma ,\Xi$ in hypernuclear matter. An ideal gas of the strange mesons K and $K^{*}$ is introduced to keep zero the net strangeness density. Our results for symmetric hypernuclear matter show that a phase transition takes place at a critical temperature around $160\pm 10$ MeV in which the scalar mean fields $\sigma ,\zeta$ take nonzero values at zero baryon density. Furthermore, the bag parameters of the baryons decrease significantly at and above this critical temperature, indicating the onset of quark deconfinement. The present results imply that the onset of quark deconfinement in SU(3) hypernuclear matter is much stronger than in SU(2) nuclear matter.

We study the instabilities of quark matter in the framework of a generalized Nambu–Jona-Lasinio model, in order to explore possible competition between three-quark clustering to form nucleons and diquark formation leading to color superconductivity. Nucleon and $\Delta$ solutions are obtained for the relativistic Faddeev equation at finite density and their binding energies are compared with those for the scalar and axial-vector diquarks found from the Bethe-Salpeter equation. In a model with interactions in both scalar and axial diquark channels, bound nucleons exist up to nuclear matter density. However, except at densities below about a quarter of that of nuclear matter, we find that scalar diquark formation is energetically favored. This raises the question of whether a realistic phase diagram of baryonic matter can be obtained from any model which does not incorporate color confinement.

Neutrino-induced charged- and neutral-current reactions play an important role during and after the r process, if the latter occurs in an environment with extreme neutrino fluxes such as the neutrino-driven wind model or neutron star mergers. Therefore consistent r-process simulations require the knowledge of neutrino-nucleus reaction rates for very neutron-rich nuclei. The neutrino reactions can excite the daughter nucleus above the neutron threshold, which are quite low for r-process nuclei. Thus the daughter nucleus will decay by emission of one or several neutrons. We have calculated the relevant total and partial neutron spallation cross sections for r-process nuclei with neutron numbers $N=41\mathrm{}–135.$ Our calculations are based on the random phase approximation and consider allowed as well as forbidden transitions.

Threshold neutral pion electroproduction on the deuteron is studied in the framework of baryon chiral perturbation theory at next-to-leading order in the chiral expansion. To this order in small momenta, the amplitude is finite and a sum of two- and three-body interactions with no undetermined parameters. We calculate the S-wave multipoles for threshold production and the deuteron S-wave cross section as a function of the photon virtuality. We also discuss the sensitivity to the elementary neutron amplitudes.

We develop a relativistic covariant and unitary description of the pion-nucleon interaction in a hadron-exchange model. The model is based on the solution of a dimensionally reduced (quasipotential) Bethe-Salpeter equation for the partial-wave off-shell $\pi N$ scattering amplitudes with the potential consisting of the field-theoretical s- and u-channel nucleon, Roper, Delta, $D_{13},$ $S_{11}$ exchanges, and the t-channel $\rho$ and $\sigma$ meson exchanges. The contributions of the spin-3/2 Delta and $D_{13}$ resonances are treated within the Rarita-Schwinger formalism and different forms of the $\pi N\Delta$ vertex are investigated. The free parameters of the model are fitted to the $\pi N$ phase-shift data of the KH80 and SM95 partial-wave analyses in the region up to 600 MeV pion kinetic energy. The resulting on-shell solution provides a good description of the $\pi N$ scattering lengths, as well as the energy behavior of the S, P, and D partial waves. The sensitivity of the phase shifts on various model-dependent effects is examined.

Shell effects in nuclei about the stability line are investigated within the framework of the relativistic Hartree-Bogoliubov (RHB) theory with self-consistent finite-range pairing. Using two-neutron separation energies of Ni and Sn isotopes, the role of $\sigma -$ and $\omega$-meson couplings on the shell effects in nuclei is examined. It is observed that the existing successful nuclear forces (Lagrangian parameter sets) based upon the nonlinear scalar coupling of the $\sigma$ meson exhibit shell effects which are stronger than suggested by the experimental data. We have introduced nonlinear vector self-coupling of the $\omega$ meson in the RHB theory. It is shown that the inclusion of the vector self-coupling of the $\omega$ meson in addition to the nonlinear scalar coupling of the $\sigma$ meson provides a good agreement with the experimental data on shell effects in nuclei about the stability line. A comparison of the shell effects in the RHB theory is made with the Hartree-Fock-Bogoliubov approach using the Skyrme force SkP. It is shown that the oft-discussed shell quenching with SkP is not consistent with the available experimental data.

The tail of the equilibrium distribution of compound-nucleus shapes is shown to extend out to very deformed shapes even for a moderate excitation energy of 100 MeV. The standard Hauser-Feshbach formalism is extended to predict the decay of a deformed compound nucleus as a function of spin, spin projection, and excitation energy. The inclusion of the equilibrium distributions of shapes is found to have little effect on the predicted neutron and proton kinetic energy spectra, but for $\alpha$ particles, the low-energy “sub-barrier” region of the spectrum is enhanced, in agreement with experimental data. Langevin simulations, using dissipation given by the wall formula, predict that compound nuclei start evaporating before the shape distribution equilibrates for excitation energies above $\sim 100\mathrm{MeV}.$

Inclusive cross sections for positive pion absorption leading to final states including two or more protons have been measured with a large solid angle detector for incident pion energies from 30 to 135 MeV for targets with $A=2\mathrm{}–208.$ The mass dependences for the inclusive $({\pi }^{+},2p),$ $({\pi }^{+},3p),$ and total absorption cross sections for multiproton final states were found to be proportional to $A^n$ with $n\approx \mathrm{0.5.}$ These cross sections also were observed to have an energy dependence at energies below 150 MeV reflective of the importance of the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonance, similar to that observed for $\pi \overrightarrow{d}\mathrm{pp}.\mathrm{}$ The inclusive cross sections for $({\pi }^{+},4p)$ were found to be less than 10 mb for all targets at all energies. Estimates were also obtained for cross sections for pion absorption leading to $2p1n$ and $3p1n$ final states. Quasideuteron absorption contributions increase slowly with A, and the energy dependence of those contributions mirrors that for $\pi \overrightarrow{d}\mathrm{pp}.\mathrm{}$ The data obtained here for multiproton final states indicate that a significant fraction of absorption events, increasing with A, most likely arises from final states containing fewer than two protons.

The new high precision data on charmonium production in proton-nucleus collisions by the E866/NuSea Collaboration at Fermilab allow us—together with older data at lower energies—to fix a unique set of parameters for the standard production and absorption scenario of charmonium in a proton-nucleus reaction. In this scenario the $c\overline{c}$ pair is formed in an octet state, emits a gluon, and continues its radial expansion in a singlet state until it has reached the charmonium radius. In all three phases it can interact with the nuclear environment. We find that the lifetime of the octet state is much shorter than acceptable on physical grounds. This challenges the physical reality of the first phase in the standard scenario.

The experimental data on kaon electromagnetic form factor are analyzed both for the timelike and the spacelike momentum by using the superconvergent dispersion relation, which we proposed to synthesize the asymptotic property of QCD and the vector meson dominance model in the low momentum region. As in the case of the pion electromagnetic form factor, the experimental data on the kaon form factor are realized by our formula very well by using the three loop approximation for the effective coupling constant. The boson form factor is sensitive to the approximation on the QCD term.

Nonlinear electron-screening corrections of stellar nuclear fusion rates are calculated analytically in the framework of the Debye-Hückel model and compared with the respective ones of Salpeter’s weak screening approximation. In typical solar conditions, the deviation from Salpeter’s screening factor is less than one percent, while for hotter stars such corrections turn out to be of the order of 1% only over the limits of the Debye-Hückel model. Moreover, an investigation of the impact of such nonlinear screening effects on the solar neutrino fluxes yields insignificant corrections for both the $\mathrm{pp}$ and $\mathrm{CNO}$ chain reactions.

A sample containing $6.3\times {10}^{14}$ nuclei of the ${16}^{+}$ isomer of ${}^{178}\mathrm{Hf}$ having a half life of 31 years and excitation energy of 2.446 MeV was irradiated with x-ray pulses derived from a device operated at 15 mA to produce bremsstrahlung radiation with an end point energy set to be 63 keV. Gamma spectra of the isomeric target were taken with two independent Ge detectors. Intensities of the 213.4 keV ${(4\mathrm{}}^{+}\to 2^{+})$ and 325.5 keV ${(6\mathrm{}}^{+}\to 4^{+})$ transitions in the ground state band of ${}^{178}\mathrm{Hf}$ were found to increase when irradiated. The largest enhancement was $1.6\pm 0.3\%$ measured in the 213.4 keV transition. Such an accelerated decay of the ${}^{178}\mathrm{Hf}$ isomer is consistent with an integrated cross section exceeding $2.2\times {10}^{-22}{\mathrm{cm}}^2\mathrm{keV}$ if the resonant absorption takes place below 20 keV as indicated by the use of selective absorption filters in the irradiating beam.

Recent information concerning the ${}^{20}\mathrm{Na}$ level at 2643 keV is still consistent with a $J^{\pi }$ assignment of $3^{+}.$ We use new experimental information on the mirror $\gamma$-decay width, together with an evaluation of the isospin nonconserving effects, to obtain $\omega \gamma >~16\hspace{0.5em}\mathrm{meV}$ for the ${}^{19}\mathrm{Ne}(p,\gamma )$ reaction which is of interest for the astrophysical rapid-proton capture process.

Two- and three-pion correlation functions are investigated for a source that is not fully chaotic. Various models are examined to describe the source. The chaoticity and weight factor are evaluated in each model as measures of the strength of correlations and compared to experimental results. A new measure of three-pion correlation is also suggested.

By employing separable potentials for the binary, i.e., $n-n$ and n-core subsystems, we compute the three-body integral equations to solve for the $2n$-separation energies in the ground and excited states of halo nuclei like ${}^{19}\mathrm{B},$ ${}^{22}\mathrm{C},$ and ${}^{20}\mathrm{C}.$ We show through numerical analysis and also from analytical considerations that Borromean-type halo nuclei like ${}^{19}\mathrm{B}$ and ${}^{22}\mathrm{C},$ where $n-n$ and n-core are both unbound, are much less vulnerable to respond to the existence of the Efimov effect. On the contrary, those nuclei, like ${}^{20}\mathrm{C}$ in which the halo neutron is supposed to be in the intruder low lying bound state with the core, appear to be the promising candidates to search for the occurrence of Efimov states at energies below the $n-\mathrm{}\left(\mathrm{nc}\right)\mathrm{}$ breakup threshold which can be within the experimental limits to measure.

The quasielastic-two-body-scattering (QTBS) hypothesis is studied in the inclusive inelastic scattering of electrons by nuclei. A sum rule for the scaling function, and other quantitative tests, are introduced to examine to what extent observed scaling is a confirmation of the QTBS assumptions. The violation of scaling that has been observed in some regions is shown to be a consequence of quasi-inelastic production of nucleon resonances.

Asymmetric nuclear matter is studied by using an effective nuclear model in a mean-field approximation. The density, temperature, and asymmetric parameter dependence of the effective baryon mass is discussed. The liquid-gas phase transition of a system with two independent conserved charges (baryon number and isospin) is studied using the stability conditions on the free energy and Gibbs conditions for phase equilibrium. The critical temperature is calculated with and without $\rho$ meson contribution, respectively.

A crucial input for recent meson hyperon cloud model estimates of the nucleon matrix element of the strangeness current is the nucleon-hyperon-$K^{*}$ ${(NYK}^{*})$ form factors which regularize some of the arising loops. Prompted by new and forthcoming information on these form factors from hyperon-nucleon potential models, we analyze the dependence of the loop model results for the strange-quark observables on the ${\mathrm{NYK}}^{*}$ form factors and couplings. We find, in particular, that the now generally favored soft $N\Lambda K^{*}$ form factors can reduce the magnitude of the $K^{*}$ contributions in such models by more than an order of magnitude, compared to previous results with hard form factors. We also discuss some general implications of our results for hadronic loop models.