- th / 9 30 70 07 v 1 7 J ul 1 99 3 CU - TP - 598 Color Diffusion and Conductivity in a Quark - Gluon Plasma

Color diffusion is shown to be an important dissipative property of quark-gluon plasmas that rapidly damps collective color modes. We derive the characteristic color relaxation time scale, tc ≈ (3αsT log(mE/mM ))−1, showing its sensitivity to the ratio of the static color electric and magnetic screening masses. This leads to a surprisingly small color conductivity, σc ≈ 2T/ log(mE/mM ), which in fact vanishes in the semiclassical (1-loop) limit. The quark-gluon plasma (QGP) phase of QCD matter has been predicted to exhibit collective behavior similar to QED plasmas with Debye screened (color) electric interactions, collective plasmon oscillations, and collective color mode instabilities under a variety of non-equilibrium configurations (see, e.g., reviews in [1, 2, 3]). Such collective behavior of quark-gluon plasmas (QGP) may be observed experimentally via ultra-relativistic heavyion reactions if the time scales of dissipative processes that act to damp collectivity are sufficiently long. Thusfar, most studies of transport properties of QGP have focused on momentum relaxation processes to estimate viscosity and thermal conductivity coefficients, dE/dx, etc. [4, 5, 6]. Relaxation phenomena associated with the color degrees of freedom have received, on the other hand, less attention. In this letter, we derive a new transport coefficient, called color diffusion, that has no abelian analog. The related color relaxation time, tc, measures how rapidly the color of a parton precesses in an ambient fluctuating background field. 1 This work was supported by the Director, Office of Energy Research, Division of Nuclear Physics of the Office of High Energy and Nuclear Physics of the U.S. Department of Energy under Contract No DE-FG-02-93ER-40764. Supported by the AUI/RHIC Fellowship Fund; Permanent address: Kurchatov Institute, 123182 Moscow D–182, Russia