In-Medium Effects on Charmonium Production in Heavy-Ion Collisions

Charmonium production in heavy-ion collisions is investigated within a kinetic theory framework incorporating in-medium properties of open- and hidden-charm states in line with recent QCD lattice calculations. A continuously decreasing open-charm threshold across the phase boundary of hadronic and quark-gluon matter is found to have important implications for the equilibrium abundance of charmonium states. The survival of $J/\psi$ resonance states above the transition temperature enables their recreation also in the Quark-Gluon Plasma. Including effects of chemical and thermal off-equilibrium, we compare our model results to available experimental data at CERN-SPS and BNL-RHIC energies. In particular, earlier found discrepancies in the $\psi'/\psi$ ratio can be resolved.Comment: 4 pages RevTex including 4 eps-figures. v2: Minor modifications and clarifications, typos corrected, Fig. 4 update

Medium Modifications of Charm and Charmonium in High-Energy Heavy-Ion Collisions

The production of charmonia in heavy-ion collisions is investigated within a kinetic theory framework simultaneously accounting for dissociation and regeneration processes in both quark-gluon plasma (QGP) and hadron-gas phases of the reaction. In-medium modifications of open-charm states (c-quarks, D-mesons) and the survival of J/psi mesons in the QGP are included as inferred from lattice QCD. Pertinent consequences on equilibrium charmonium abundances are evaluated and found to be especially relevant to explain the measured centrality dependence of the psi'/psi ratio at SPS. Predictions for recent In-In experiments, as well as comparisons to current Au-Au data from RHIC, are provided.Comment: 4 Latex pages including 4 eps figures and IOP style files. Talk given at the 17th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2004, Oakland, CA USA, 11-17 Jan 2004. To appear in J. Phys.

Quarkonia and Heavy-Quark Relaxation Times in the Quark-Gluon Plasma

A thermodynamic T-matrix approach for elastic 2-body interactions is employed to calculate spectral functions of open and hidden heavy-quark systems in the Quark-Gluon Plasma. This enables the evaluation of quarkonium bound-state properties and heavy-quark diffusion on a common basis and thus to obtain mutual constraints. The two-body interaction kernel is approximated within a potential picture for spacelike momentum transfers. An effective field-theoretical model combining color-Coulomb and confining terms is implemented with relativistic corrections and for different color channels. Four pertinent model parameters, characterizing the coupling strengths and screening, are adjusted to reproduce the color-average heavy-quark free energy as computed in thermal lattice QCD. The approach is tested against vacuum spectroscopy in the open (D, B) and hidden (Psi and Upsilon) flavor sectors, as well as in the high-energy limit of elastic perturbative QCD scattering. Theoretical uncertainties in the static reduction scheme of the 4-dimensional Bethe-Salpeter equation are elucidated. The quarkonium spectral functions are used to calculate Euclidean correlators which are discussed in light of lattice QCD results, while heavy-quark relaxation rates and diffusion coefficients are extracted utilizing a Fokker-Planck equation.Comment: 33 pages, 28 figure

INTEGRATED MANAGEMENT OF COMMON REED ALONG THE PLATTE RIVER IN NEBRASKA: CONTROL, TIMING, WATER USE, AND ECONOMIC ANALYSIS

There are two biotypes of common reed, which includes the native common reed (Phragmites australis subsp. americanus) and non-native (invasive) common reed (Phragmites australis subsp. australis).The non-native biotype of common reed has invaded wetland habitats in many states of the US, including Nebraska. Three studies, disking followed by herbicide, mowing followed by herbicide, and herbicide followed by mechanical treatment were initiated in 2008 in Nebraska. The objective was to evaluate common reed control along the Platte River using an integrated management. Herbicide followed by mechanical treatment had excellent control (≥92%) with all treatments except glyphosate applied in the summer of 2008 alone or followed by a mechanical treatment 817 DAT. Field studies were conducted the Platte River with the objective to determine the effect of herbicide selection and timing of application on common reed. Three herbicides were applied at two rates and three growth stages of common reed. In general, common reed showed more tolerance to applications during vegetative stage, with control ratings increasing with later timings. Imazapyr provided the highest levels of control (≥92%) across all three timings, while imazamox provided the lowest level of control 60%). Measurements of gas exchange and leaf area index were collected in undisturbed stands of both native and non-native common reed stands. Stomatal conductance and leaf assimilation on average was higher in native common reed than in non-native common reed. LAI in invasive common reed was dramatically larger on average. There was 243 mm year-1 estimated difference in transpiration with non-native common reed having a higher estimation of transpiration. An economic analysis of common reed management options reflecting water savings and net return on investment was performed. Returns ranged from $1,326 to$4,235 per hectare over three years. Treatments of disking followed by herbicide tended to have the highest initial net return. All treatments provided a net gain return after 3 years of control of common reed

An apparent statistical relationship between polar heat budget and zonal circulation

Apparent statistical correlation between Arctic heat budget and zonal circulatio

Toward the theory of strongly coupled Quark-Gluon Plasma

We review recent progress toward understanding of sQGP. The phenomenological part includes discussion of elliptic and conical flows at RHIC. Then we proceed to first quantum mechanical studies of manybody states at $T>Tc$, the ``polymeric chains'' $\bar q.g.g... q$ and baryons. A new model for sQGP is a classical dynamical system, in which color vector is changed via the Wong equation. First Molecular Dynamics (MD) results for its diffusion and viscosity are reported. Finally we speculate how strong correlations in matter may help solve puzzles related to jet quenching, both the magnitude and angular distribution.Comment: A plenary talk at Quark Matter 05, Budabest, Aug.200

Medium Dependence of the Vector-Meson Mass: Dynamical and/or Brown-Rho Scaling?

We discuss the similarities and differences for the theories of Rapp, Wambach and collaborators (called R/W in short) and those based on Brown-Rho scaling (called B/R), as applied to reproduce the dileptons measured by the CERES collaboration in the CERN experiments. In both theories the large number of dileptons at invariant masses $\sim$~$m_\rho/2$ are shown to be chiefly produced by a density-dependent $\rho$-meson mass. In R/W the medium dependence is dynamically calculated using hadronic variables defined in the matter-free vacuum. In B/R scaling it follows from movement towards chiral symmetry restoration due to medium-induced vacuum change, and is described in terms of constituent (or quasiparticle) quarks. We argue that the R/W description should be reliable up to densities somewhat beyond nuclear density, where hadrons are the effective variables. At higher density there should be a crossover to constituent quarks as effective variables scaling according to B/R. In the crossover region, the two descriptions must be ``dual''.Comment: 13 pages LaTeX, incl. 5 eps-figures and appb.sty; Talk given at the Workshop on 'The Structure of Mesons, Baryons and Nuclei', Cracow, May 1998, in honor of J. Speth's 60th birthday, to be published in Acta Physica Polonica