Heavy quarkonium and color screening

1. Strongly coupled plasmas, RIKEN-BNL, December 16-17, 2004 Heavy quarkonium and color screening Dmitri Kharzeev BNL

2. Outline • QCD and asymptotic freedom • Heavy quarkonium - the hydrogen atom of QCD • Strongly coupled QGP • Heavy quarkonium in sQGP

3. Constituents of matter

4. Quarks and the Standard Model Charm and bottom quarks are heavy on typical QCD scale of ~ 200 MeV, and live long enough to form bound states (charmonium and bottomonium)

5. “November revoluton” The discovery of quarkonium

6. Heavy quarkonium Why is heavy quarkonium so narrow?

7. QCD and the “dark mass” of the proton QCD = Quark Model + Gauge Invariance Invariant under scale ( ) and chiral (left <-> right) .i transformations in the limit of massless quarks (u, d) Experiment: quarks are almost massless… … but then… all hadrons must be massless as well! Where does the “dark mass” of the proton come from? Classical scale, UA(1) symmetries broken by quantum effects

8. QCD and quantum anomalies Classical scale invariance is broken by quantum effects: renormalization introduces a dimensionful parameter, and gives birth to scale anomaly HHHi Hadrons get masses coupling runs with the distance

9. Asymptotic Freedom At short distances, the strong force becomes weak - anti-screening Gross, Wilczek; Politzer ‘74 Heavy quarkonia are small, R ~ 1/ (M g2), so should be possible to describe by weak coupling methods

10. Coulomb potential in QCD Spectral representation in the t-channel: If physical particles can be produced (positive spectral density), then unitarity implies screening Gluons Quarks (transverse)

11. Coulomb potential in QCD - II Missing non-Abelian effect: instantaneous Coulomb exchange dressed by (zero modes of) transverse gluons Negative sign (the shift of the ground level due to perturbations - unstable vacuum! ): Gribov ‘78 Review: Yu.Dokshitzer & DK, hep-ph/0404216 Anti-screening

12. Screening in Quark-Gluon Plasma These diagrams are enhanced at finite temperature: (scattering off thermal gluons and quarks) This diagram is not: => At high enough T, screening wins

13. Screening in the QGP T-dependence of the running coupling develops in the non-perturbative region at T < 3 Tc F.Karsch, P.Petreczky et al

14. Strongly coupled QCD plasma Interactions are important! (the “dark mass” of the Quark-Gluon Plasma) C. Bernard, T.Blum, … F. Karsch, P.Petreczky, ..

15. Heavy quarkonium as a probe the link between the observables and the McLerran-Svetitsky confinement criterion

16. Gluo-effect: quarkonium ionization Confined phase - soft gluons (mostly at small x) Deconfined phase - hard gluons k ~ 3 T DK, H.Satz ‘94 effective “gluo-effect” ionization E.Shuryak ‘78 DK, H.Satz, hep-ph/9505345

17. What mechanism is more important? Strongly coupled regime: DE/T >> 1 Ionization Weakly coupled regime: DE/T << 1 Screening DK, H.Satz, hep-ph/9505345

18. What mechanism is more important? DK, L.McLerran, H.Satz hep-ph/9504338 Weak coupling: Strong coupling:

19. Heavy quark internal energy above T O.Kaczmarek, F. Karsch, P.Petreczky, F. Zantow, hep-lat/0309121

20. Heavy quarkonia above Tc F.Karsch, P.Petreczky, K.Petrov, F.Zantow, … M.Asakawa, T.Hatsuda

21. Experimental information CERN: NA38/50/60 experiments NA50 Coll., hep-ex/0412036

22. Experimental information RHIC@BNL: PHENIX experiment NA50 Coll., hep-ex/0412036

23. Dy = 1.0 Coalescence model (Thews et al) Dy = 4.0 Stat. Model (Andronic et al.) Absorption model (Grandchamp et al.) Experimental information RHIC@BNL: PHENIX experiment PRC 69, 014901 (2004)

24. Summary 1. Heavy quarkonium is an excellent probe of the deconfinement phase transition 2. Detailed information available from the lattice calculations 3. Experimental evidence of quarkonium suppression in nuclear collisions at SPS and RHIC 4. Good theoretical understanding lacking