Complex Plasmas as a Model for the QuarkGluonPlasma

Complex Plasmas as a Model for the Quark-Gluon-Plasma Liquid Markus H. Thoma* Max-Planck-Institute for Extraterrestrial Physics 1. Strongly Coupled Plasmas 2. Complex Plasmas 3. Applications to the Quark-Gluon Plasma * Supported by DLR (BMBF)

1. Strongly Coupled Plasmas Plasma = ionized gas, 99% of visible matter in Universe Plasmas generated by high temperatures, electric fields, or radiation Classifications: 1. Non-relativistic – relativistic plasmas (pair plasmas, QGP) 2. Classical – quantum plasmas (white dwarfs, QGP) 3. Ideal – strongly coupled plasmas (complex plasmas, QGP)

Coulomb coupling parameter Q: charge of plasma particles d: inter particle distance T: plasma temperature Ideal plasmas: G << 1 (most plasmas: G < 10 -3) Strongly coupled plasmas: G > O (1) Examples: ion component in white dwarfs, high-density plasmas at GSI Non-perturbative description, e. g. , molecular dynamics One-component plasma, pure Coulomb interaction (repulsive): G > 172 g Coulomb crystal

Debye screening g Yukawa systems Additional parameter: k = d/l. D Liquid phase: G > O (1) Purely repulsive interaction g no gas-liquid transition, only supercritical fluid

2. Complex Plasmas Dusty or complex plasmas = multi component plasmas containing ions, electrons, neutral gas, and microparticles, e. g. , dust Example: low temperature neon plasma in a dc- or rf discharge

Injection of microparticles with diameter 1 – 10 mm High electron mobility g microparticles collect electrons on surface g large negative charge: Q = 103 – 105 e Inter particle distance about 200 mm g G >> 1 g plasma crystal (predicted 1986, discovered 1994 at MPE) Observation: illumination by laser sheet and recorded by CCD camera

Melting of plasma crystal by pressure reduction gless neutral gas friction gtemperature increase gdecrease of Coulomb coupling parameter G = Q 2/(d. T)

Quantitive analysis of equation of state and determination of G: pair correlation function Crystal: long range order g sharp peaks at the nearest neighbors, next to nearest neighbors and so on Liquid: short range order (incompressibility) gonly one clear peak corresponding to inter particle distance plus one or two broad and small peaks Gas: no order gno clear peaks

Gravity has strong influence on microparticles gmicrogravity experiments

Applications of complex plasmas: 1. Model system for phase transitions, crystallization, dynamical behavior of liquids and plasmas on the microscopic level 2. Astrophysics: comets, interstellar plasmas, star and planet formation, planetary rings, … 3. Technology: plasma coating and etching, e. g. microchip production, problem: dust contamination

3. Applications to the Quark-Gluon Plasma Estimate of interaction parameter C = 4/3 (quarks), C = 3 (gluons) T = 200 Me. V g a. S = 0. 3 - 0. 5 d = 0. 5 fm Ultrarelativistic plasma: magnetic interaction as important as electric g. G = 1. 5 – 6 g QGP Liquid? RHIC data (hydrodynamical description with small viscosity, fast thermalization) indicate QGP Liquid Attractive and repulsive interaction g gas-liquid transition at a temperature of a few hundred Me. V

Static structure function (Fourier transform of pair correlation function) g experimental and theoretical analysis of liquids Hard Thermal Loop approximation (T >> Tc): ginteracting gas QCD lattice simulations g QGP liquid?

Strongly coupled plasmas g cross section enhancement Reason: Coulomb radius, r. C = Q 2/E, larger than Debye screening length l. D = 1/m. D g modification of Coulomb scattering theory g enhancement of ion-microparticle interaction (ion drag force) QGP: r. C /l. D = 1 – 5 g parton cross section enhancement by factor 2 – 9 gsmall mean free path l (corresponding to small viscostity h ~ l) and fast thermalization. Additional cross section enhancement by non-linear and non-perturbative effects Implication: enhancement of collisional energy loss, suppression of radiative energy loss by LPM effect (formation time) g jet quenching

Conclusions • Strongly coupled plasmas are of increasing importance in fundamental research as well as technology • QGP and complex plasmas are important examples of strongly coupled plasmas • QGP is the most challenging strongly coupled plasma • Complex plasmas can easily be studied and used as a model for the QGP (phase transitions, correlation functions, cross sections, …) • RHIC and ISS provide very important information on strongly coupled plasmas