119797569
Collective flow of pions in relativistic heavy-ion collisions
Abstract 3he transverse-momentum distributions of pions in the Au(1 GeV/nucleon) + Au collisions are analyzed. The calculations are carried out within relativistic mean-field one- and two-fluid models. The rapidity distributions of the mean transverse momentum of pions are found to be fairly sensitive to the nuclear equation of state and, especially, to the stopping power. It is shown that the collective flow of pions in the reaction plane always correlates with the “hot” flow of nucleons (i.e. those emitted from hot regions of nuclear system), while not always with the total nucleon flow. This “hot” nucleon flow can be experimentally singled out by selecting nucleons with sufficiently high transverse momenta. We predict that the “hot” nucleon flow selected in this way will always correlate with the pion flow. Available experimental data on transverse-momentum spectra of pions are compared with calculations employing various equations of state and stopping power.
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.
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.
115321070
On the relationship between Boltzmann-Langevin and Boltzmann-Uehling-Uhlenbeck models
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.
896237
Electroproduction of charmonia off nuclei
In a recent publication we have calculated elastic charmonium production in ep collisions employing realistic charmonia wave functions and dipole cross sections and have found good agreement with the data in a wide range of s and Q^2. Using the ingredients from those calculations we calculate exclusive electroproduction of charmonia off nuclei. Here new effects become important, (i) color filtering of the c-cbar pair on its trajectory through nuclear matter, (ii) dependence on the finite lifetime of the c-cbar fluctuation (coherence length) and (iii) gluon shadowing in a nucleus compared to the one in a nucleon. Total coherent and incoherent cross sections for C, Cu and Pb as functions of s and Q^2 are presented together with some differential cross sections. The results can be tested with future electron-nucleus colliders or in peripheral collisions of ultrarelativistic heavy ions.
120657056
Radiative tau decay into pion
The possibility of the experimental investigation of the radiative tau decay into pion is discussed including background conditions. The decay width is estimated to be Br(τ→vτπγ)=0.15% (at the minimal registered photon energy 50 MeV). The contribution of the structural component is 10% of the total radiation. The main background is produced by photons from the τ→vτπ−π0 decay. We investigate the angular and energy spectra of the decay products and analyse the background conditions. The kinematic region was found where the structural radiation dominates over background.
118188860
Vector meson production in ultra-peripheral collisions at LHC
Vector meson production in ultra-peripheral collisions of heavy ions at LHC is calculated in VDM and color dipole approaches.
182081169
PHOTON PROPAGATOR ASYMPTOTICS AT Q**2 ---> infinity IN THE SOURCE THEORY