K. Tywoniuk

Charmonium dissociation and recombination at RHIC and LHC

AbstractCharmonium production at heavy-ion colliders is considered within the comovers-interaction model. The formalism is extended by including possible secondary J/ψ production through recombination and an estimate of recombination effects is made without adjusting the model parameters. The comovers-interaction model also includes a comprehensive treatment of initial-state nuclear effects, which are discussed in the context of such high energies. With these tools, the model properly describes the centrality and the rapidity dependence of experimental data at RHIC energy, n

Gluon shadowing in the Glauber–Gribov model at HERA

sqrt{s}=200

Massless Mode and Positivity Violation in Hot QCD

nxa0GeV, for both Au+Au and Cu+Cu collisions. Predictions for LHC, n

Microscopic models and effective equation of state in nuclear collisions in the vicinity of

sqrt{s}=5.5

E_{\rm lab} = 30A

nxa0TeV, are presented and the assumptions and extrapolations involved are discussed.

GeV at the GSI Facility for Antiproton and Ion Research (FAIR) and beyond

Abstract We calculate shadowing using new data on the gluon density of the pomeron recently measured with high precision at HERA. The calculations are made in a Glauber–Gribov framework and pomeron tree-diagrams are summed up within a unitarity-conserving procedure. The total cross section of γ ∗ A interaction is then found in a parameter-free description, employing gluon diffractive and inclusive distribution functions as input. A strong shadowing effect is obtained, in a good agreement with several other models. Impact parameter dependence of gluon shadowing is also presented.

Elliptic flow at RHIC : Where and when was it formed?

We calculate the quark self-energy at one-loop level at high temperature, taking into account contributions from both the (chromo)electric scale gT and the (chromo)magnetic scale g^{2}T. While reproducing standard massive excitations due to the electric scale, we uncover a novel massless excitation ascribable to the magnetic scale. The residue of this massless excitation is nonpositive at all temperatures, which consequently gives rise to positivity violation in the quark spectral functions. This demonstrates the profound impact of confinement effects on thermal quark collective excitations, which manifest genuine long-range correlations in the system.

Coherent J/ψ production - a novel feature at LHC?

Two microscopic models, UrQMD and QGSM, were employed to study the formation of locally equilibrated hot and dense nuclear matter in heavy-ion collisions at energies from 11.6A GeV to 160A GeV. Analysis was performed for the fixed central cubic cell of volume V = 125 fm and for the expanding cell which followed the growth of the central area with uniformly distributed energy. To decide whether or not the equilibrium was reached, results of the microscopic calculations were compared to that of the statistical thermal model. Both dynamical models indicate that the state of kinetic, thermal and chemical equilibrium is nearly approached at any bombarding energy after a certain relaxation period. The higher the energy, the shorter the relaxation time. Equation of state has a simple linear dependence P = a( √ s)ε, where a ≡ c2s is the sound velocity squared. It varies from 0.12± 0.01 at Elab = 11.6A GeV to 0.145± 0.005 at Elab = 160A GeV. Change of the slope in a( √ s) behavior occurs at Elab = 40A GeV and can be assigned to the transition from baryon-rich to meson-dominated matter. The phase diagrams in the T − μB plane show the presence of kinks along the lines of constant entropy per baryon. These kinks are linked to the inelastic (i.e. chemical) freeze-out in the system.

Charmonium dynamics in dA and AA at RHIC and LHC

Abstract Evolution of the elliptic flow of hadrons in heavy-ion collisions at RHIC energies is studied within the microscopic quark–gluon string model. The elliptic flow is shown to have a multi-component structure caused by (i) rescattering and (ii) absorption processes in spatially asymmetric medium. Together with different freeze-out dynamics of mesons and baryons, these processes lead to the following trend in the flow formation: the later the mesons are frozen, the weaker their elliptic flow, whereas baryon fraction develops stronger elliptic flow during the late stages of the fireball evolution. The phase-space distributions of the emitted particles are studied as well. The flow is shown to be formed both in the central and in the fragmentation regions of the reaction. Comparison with the PHOBOS data demonstrates the model ability to reproduce the v 2 ch ( η ) signal in different centrality bins.

Nuclear suppression at RHIC and LHC in Glauber–Gribov approach

Abstract Energy dependence of heavy quarkonia production in hadron–nucleus collisions is studied in the framework of the Glauber–Gribov theory. We emphasize a change in the space–time picture of heavy-quark state production on nuclei with energy. Longitudinally ordered scattering of a heavy-quark system takes place at low energies, while with increasing energy it transforms to a coherent scattering of projectile partons on the nuclear target. The characteristic energy scale for this transition depends on masses and rapidities of produced particles. For J / ψ , produced in the central rapidity region, the transition happens at RHIC energies. The parameter-free calculation of J / ψ in dAu collisions is in good agreement with recent RHIC data. We use distributions of gluons in nuclei to predict suppression of heavy quarkonia at LHC.