120466205
Elliptic Flow and Dissipation at AGS - SPS Energies
Elliptic flow in heavy-ion collisions at incident energies ${E}_{\text{lab}}\ensuremath{\simeq}(1\char21{}160)A$ GeV is analyzed within the model of three-fluid dynamics (3FD). We show that a simple correction factor, taking into account dissipative effects, allows us to adjust the 3FD results to experimental data. This single-parameter fit results in a good reproduction of the elliptic flow as a function of the incident energy, centrality of the collision, and rapidity. The experimental scaling of pion eccentricity-scaled elliptic flow versus charged-hadron-multiplicity density per unit transverse area also turns out to be reasonably described. Proceeding from values of the Knudsen number, deduced from this fit, we estimate the upper limit of the shear viscosity-to-entropy ratio as $\ensuremath{\eta}/s~1\char21{}2$ at the CERN Super Proton Synchrotron (SPS) incident energies. This value is of the order of minimal $\ensuremath{\eta}/s$ observed in water and liquid nitrogen.
14791019
Lattice QCD constraints on hybrid and quark stars
A QCD-motivated dynamical-quasiparticle model with parameters adjusted to reproduce the lattice-QCD equation of state is extrapolated from the region of high temperatures and moderate baryonic densities to the domain of high baryonic densities and zero temperature. The resulting equation of state matched with realistic hadronic equations of state predicts a phase transition into the quark phase at higher densities than those reachable in neutron star interiors. This excludes the possibility of the existence of hybrid (hadron-quark) stars. Pure quark stars are possible and have low masses, small radii, and very high central densities. Similar results are obtained for a simple bag model with massive quarks, fitted to reproduce the same lattice results. Self-bound quark matter is also excluded within these models. Uncertainties in the present extrapolation are discussed. Comparison with standard bag models is made.
195334493
Quantum simulations of strongly coupled quark-gluon plasma
A strongly coupled quark-gluon plasma (QGP) of heavy constituent quasi-particles is studied by a path-integral Monte-Carlo method. This approach is a quantum generalization of the classical molecular dynamics by Gelman, Shuryak, and Zahed. It is shown that this method is able to reproduce the QCD lattice equation of state. The results indicate that the QGP reveals liquid-like rather than gaslike properties. Quantum effects turned out to be of prime importance in these simulations.
18368050
Equation of State of Strongly Coupled Quark–Gluon Plasma – Path Integral Monte Carlo Results
A strongly coupled plasma of quark and gluon quasiparticles at temperatures from 1.1Tc to 3Tc is studied by path integral Monte Carlo simulations. This method extends previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime. We present the equation of state and find good agreement with lattice results. Further, pair distribution functions and color correlation functions are computed indicating strong correlations and liquid-like behavior (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
118142337
Partial-transparency effects in high-energy collisions of heavy ions
A model is proposed for heavy-ion collisions at E/sub lab/approx.1 GeV/nucleon for the case of an incomplete statistical equilibrium in the highly excited nuclear matter. This approach can reproduce the characteristic double-humped structure of the experimental rapidity distributions of secondary particles.
115321070
On the relationship between Boltzmann-Langevin and Boltzmann-Uehling-Uhlenbeck models
12114990
Pion Observables in the Extended NJL Model with Vector and Axial-Vector Mesons☆
Abstract The momentum-space bosonization method of a Nambu and Jona-Lasinio type model with vector and axial-vector mesons is applied to ππ scattering. Unlike the case in earlier published papers, we obtain the ππ scattering amplitude using the linear and nonlinear realizations of chiral symmetry and fully taking into account the momentum dependence of meson vertices. We show the full physical equivalence between these two approaches. The chiral expansion procedure in this model is discussed in detail. Chiral expansions of the quark mass, pion mass and constant f π are obtained. The low-energy ππ phase shifts are compared to the available data. We also study the scalar form factor of the pion.
118014393
QCD analysis of deep inelastic lepton-scattering data
We have carried out a QCD analysis of data on deep inelastic lepton-scattering (using data of the collaborations BCDMS, EMC, and CDHS) in the leading and next-to-leading orders in the coupling constant ..cap alpha../sub s/. We have considered the effect of the sea quarks and gluons. We discuss the dependence of our results for ..lambda.. on effects of twist corrections, nuclear target effects, and heavy-quark production thresholds.
119138207
Lepton flavor violating photoleptonic effect
We study lepton flavor violating analogs of the photoelectric effect, with a final μ or T instead of an electron: γe → μ and γe → T. On the basis of the general parametrization of the matrix element of the electromagnetic current we estimate the upper limits for the cross sections and event rates of these processes, imposed by the current experimental bounds on μ → ey and T → eγ decays.
6453654
Photoproduction of charmonia and total charmonium proton cross-sections
Elastic virtual photoproduction cross sections ${\ensuremath{\gamma}}^{*}\stackrel{\ensuremath{\rightarrow}}{p}J/\ensuremath{\psi}({\ensuremath{\psi}}^{\ensuremath{'}})p$ and total charmonium-nucleon cross sections for $J/\ensuremath{\psi}, {\ensuremath{\psi}}^{\ensuremath{'}},$ and $\ensuremath{\chi}$ states are calculated in a parameter-free way with the light-cone dipole formalism and the same input: factorization in impact parameters, light-cone wave functions for the ${\ensuremath{\gamma}}^{*}$ and the charmonia, and the universal phenomenological dipole cross section which is fitted to other data. The charmonium wave functions are calculated with four known realistic potentials, and two models for the dipole cross section are tested. Very good agreement with data for the cross section of charmonium photoproduction is found in a wide range of s and ${Q}^{2}.$ The inclusion of the Melosh spin rotation increases the ${\ensuremath{\psi}}^{\ensuremath{'}}$ photoproduction rate by a factor of 2\char21{}3 and removes previously observed discrepancies in the ${\ensuremath{\psi}}^{\ensuremath{'}}$ to $J/\ensuremath{\psi}$ ratio in photoproduction. We also calculate the charmonium-proton cross sections whose absolute values and energy dependences are found to correlate strongly with the sizes of the states.
126120440
Spectra Particles From $\Lambda_c^+$ and $\Sigma_c^{++}$ Charmed Baryon Decays Produced in Neutrino $N$ Interactions