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QCD and Heavy-ion Collisions

QCD and Heavy-ion Collisions. 王新年. 相对论重离子碰撞与低能强子物理讨论会 威海 , 2004 年 8 月报 3-7 日. LBNL. Heavy-ion Collisions. RHIC BNL. Au+Au up to 200 GeV/n. QCD Theory. (approx.)Chiral symmetry and its spontaneous breaking Goldstone boson and chiral condensate Scale and U A (1) anomaly

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QCD and Heavy-ion Collisions

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  1. QCD and Heavy-ion Collisions 王新年 相对论重离子碰撞与低能强子物理讨论会 威海, 2004年 8 月报3-7 日 LBNL

  2. Heavy-ion Collisions RHIC BNL Au+Au up to 200 GeV/n

  3. QCD Theory • (approx.)Chiral symmetry and its spontaneous breaking • Goldstone boson and chiral condensate • Scale and UA(1) anomaly • SU(3) gauge symmetry (non-Abelian) • Confinement at long distance • Asymptotic freedom at short distance • ….

  4. Chiral Symmetry Chirality of massless quarks: Chiral symmetry: Or alternatively: Conserved currents: Spontaneously broken: Goldstone bosons (p,K,h)

  5. Chiral symmetry restoration Restoration at high temperature F. Karsch ‘2001 Brown-Rho postulation:

  6. UA(1) Anomaly U(1) and UA(1) Symmetry: (Classically) conserved current: Spontaneous chiral symmetry breaking  9th Goldstone boson (h0) A0m not a conserved current UA(1) is broken in quantum theory: Chiral anomaly Alder&Jackiw Topological susceptibility

  7. Partial restoration of UA(1) Z. Huang & XNW UA(1) restored phase could lead to false vacuum Massive parity violation Kharzeev & Pisarski

  8. S Bethke J.Phys. G26 (2000) R27 Running of as(Q) SU(3) Gauge Symmetry Non-abelian interaction Anti-screening of color Asymptotic freedom Gross,Wilczek;Politzer (73)

  9. Ideal Gas Approximation • Leading orders inperturbation (Kapusta) • Failure of simple perturbation: (non-convergenceg g~1)(Arnold & Zhai ’94) • Expand contributions from soft modes k~ gT in terms of g.

  10. … + + = Resummation of HTL • Resummation of Hard Thermal Loops(Braaten & Pisarski) • Effective theory integrating out “hard” (k~T) loops • Resummation of HTP (Weldon’94) Debye mass

  11. Quasi-partciles & Self-consistent Resummation • Quasi-particles with dispersion given by HTL • Self-consistentresummation: • Dyson’s equation

  12. Scale Anomaly • Scale invariance (massless quarks) • QCD interaction  renormalization of g(l) • Break scale invariance  scale anomaly Classically conserved dilation current Bag constant Gluon condensate

  13. QCD Phase transition • Ideal quark and gluon gas • Massless pion gas • First order phase transition: P T4 Tc4 e T4 Tc4

  14. Lattice QCD results F. Karsch ‘2001

  15. Confinement-deconfinement SU(3) non-Abelian gauge interaction  confinement Heavy quark potential: Karsch, Laermann and Peikert 2001 J/Y suppression

  16. QGP in AA Collision? ? QGP Expanding, short-lived, small volume • Criteria: • High density: e>>ec • Large volume: V>>l (mean-free-path) • Long life-time: t>>l • Local thermal equilibration (interaction): approximately • parton degrees of freedom • Debye screening of strong interaction: deconfinement

  17. e- Energy Loss & Jet Quenching BDPM Gyulassy Vitev Levai Wang & Wang Wiedemann; Zakharov

  18. Single hadron suppression NLO calc. H.-Z. Zhang

  19. Suppression of away-side jet Df

  20. Single hadron Azimuthal anisotropy I

  21. GeV for E=10 GeV Consistent with estimate of initial condition dE/dx and gluon density at RHIC From RHIC data of Au+Au Collisions Initial Density about 30 times of that in a Cold Au Nucleus

  22. py px Elliptic Flow Coordinate space: initial asymmetry Pressure gradient diff Hydro-dynamics calc. Momentum space: final asymmetry

  23. Early Thermalization U. Heinz nucl-th/0407067 Constraint on thermalization time

  24. Parton recombination -> Partonic degrees of freedom Flavor of Jet Quenching

  25. Summary • Heavy-ion collisions can test many properties of QCD • Deconfinement phase transition • Chiral symmetry restoration • Current RHIC data indicate formation of QGP • High energy density 20 GeV/fm (t0=1 fm/c)from jet quenching, dN/dy, radial flow • Jet quenching  Strong parton interaction thermalizationv2  early thermalization • Parton recombination  partonic matter • More experimental studies to come • Heavy-quark energy loss (B.-W. Zhang)

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