Denes Molnar

Elliptic flow at large transverse momenta from quark coalescence

We show that hadronization via quark coalescence enhances hadron elliptic flow at large p(perpendicular) relative to that of partons at the same transverse momentum. Therefore, compared to earlier results based on covariant parton transport theory, more moderate initial parton densities dN/deta(b=0) approximately 1500-3000 can explain the differential elliptic flow v(2)(p(perpendicular)) data for Au+Au reactions at sqrt[s]=130 and 200A GeV from BNL RHIC. In addition, v(2)(p(perpendicular)) could saturate at about 50% higher values for baryons than for mesons. If strange quarks have weaker flow than light quarks, hadron v(2) at high p(perpendicular) decreases with relative strangeness content.

Quark coalescence and elliptic flow of charm hadrons

Elliptic flow of charm hadrons is investigated based on the quark coalescence model. Due to the large difference between the charm quark and light quark masses, hadrons containing both light and charm quarks show a qualitatively different

Dissipative effects from transport and viscous hydrodynamics

v_2(p_\perp)

Dissipation and elliptic flow at relativistic energies.

from hadrons containing only light quarks. Simple relations are proposed to infer quark elliptic flow from those of hadrons. The effects of the finite momentum spread of hadron wavefunctions are also studied, and are found to be small for charm hadrons.

Charm elliptic flow from quark coalescence dynamics

We compare 2 → 2 covariant transport theory and causal Israel–Stewart hydrodynamics in a (2 + 1)-dimensional longitudinally boost-invariant geometry with RHIC-like initial conditions and a conformal e = 3p equation of state. The pressure evolution in the center of the collision zone and the final differential elliptic flow v2(pT) from the two theories agree remarkably well for a small shear viscosity to entropy density ratio η/s ≈ 1/(4π), and also for a large cross section σ ≈ 50 mb. A key to this agreement is keeping all terms in the Israel–Stewart equations of motion. Our results indicate promising prospects for the applicability of Israel–Stewart dissipative hydrodynamics at RHIC, provided the shear viscosity of hot and dense quark–gluon matter is indeed very small for the relevant temperatures T ~ 200–500 MeV.

The Effect of finite range interactions in classical transport theory

We compare elliptic flow evolution from ideal hydrodynamics and covariant parton transport theory, and show that, for conditions expected at RHIC, dissipation significantly reduces elliptic flow even for extreme parton cross sections and/or densities sigma_gg * dN/d\eta(b=0) ~ 45 mb * 1000. The difference between transport and hydrodynamic elliptic flow is established rather early during the evolution of the system, but the buildup of elliptic flow is surprisingly insensitive to the choice of the initial (formation or thermalization) time in both models.

Differential Freeze-Out and Pion Interferometry at RHIC from Covariant Transport Theory

From covariant transport theory, a significant ∼10% light quark elliptic flow at RHIC implies an elliptic flow of similar magnitude for charm quarks, at moderately large p T >2.5-3 GeV. At lower transverse momenta, charm quark elliptic flow reduces progressively, reminiscent of the mass ordering pattern in ideal hydrodynamics. From the quark flows we predict the elliptic flow of D mesons at RHIC via quark coalescence. The large parton opacities needed to generate the light quark flow also lead to substantial ∼40-50% secondary charm production.

Heavy quarks at RHIC from parton transport theory

The effect of scattering with non-zero impact parameters between consituents in relativistic heavy ion collisions is investigated. In solving the relativistic Boltzmann equation, the characteristic range of the collision kernel is varied from approximately one fm to zero while leaving the mean-free path unchanged. Modifying this range is shown to significantly affect spectra and flow observables. The finite range is shown to provide effective viscosities, shear, bulk viscosity and heat conductivity, with the viscous coefficients being proportional to the square of the interaction range.

Origin of the mass splitting of elliptic anisotropy in a multiphase transport model

Puzzling discrepancies between recent pion interferometry data on Au+Au reactions at square root of s=30 and 200 AGeV from RHIC and predictions based on ideal hydrodynamics are analyzed in terms of covariant parton transport theory. The discrepancies in the R(out)/R(side) ratio are significantly reduced when the finite opacity of the gluon plasma is taken into account. However, the magnitude of the radii is not well accounted for.

Origin of the mass splitting of azimuthal anisotropies in a multiphase transport model

There are several indications that an opaque partonic medium is created in energetic Au+Au collisions