Quest for Quarkonia: Challenges and Discoveries in Heavy Quark Physics

1. Quest for Quarkonia Thomas Ullrich (with help from Jamie Nagle) Joint RHIC/EIC Round Table Discussion BNL Sep 19, 2002 • Why Quarkonium? • Related problems & difficulties • Experiments (yesterday & now) • What’s left to learn in X years • Detector Requirements

2. The Original Idea and Variations • Matsui & Satz (PLB 178 (1986) 416 • J/ suppression by QGP • color screening prevents binding • color screened potential: • V(r) = -(aeff/r) exp[-r/rD(T)] • With the birth of the octet model: • QGP  hard gluons • cold matter  soft gluons • hard gluons break up octet • Heavy Quark Potential at different T • Lattice: string breaking in QCD with dynamical quarks • in-medium T dependence of heavy-quark potential • compare with binding energies of quarkonia • indication of dissociation into open charm below Tc? (F. Karsch et al. hep-lat/0012023)

3. (Only?) Thermometer for Early Times Digal, Petreczky and Satz, hep-ph/0106017 Bracketing the temperature at early times:  need J/Y and  S states  major feed-down: need to measure P states  minor feed-down: need to measure b production

4. E866, PRL 84 (2000) 3256-3260 J/, ’ Problems: Part I • We do not know how J/Y is produced • octet model is currently falling apart (e.g. Bell hep-ex/0205104) • classical vs. QFT description (Y. Dokshitzer) • Even if we understand J/Y production in pp, pA we still have to understand it in AA • possibly thermal? (PBM nucl-th/0007059) • Absorption in pA (cold matter) sJ/Y-N= 7.1 mb • Co-mover absorption in AA (less for , see Lin, Ko nucl-th/0007027) E772, PRL 66 (1991) 2285

5. Problems: Part II • Suppression relative to what? • Drell-Yan (SPS) • Open charm background (RHIC) • Z (LHC) • or relative to geometry Npart, Nbin (Glauber) • Supression as a function of what? • centrality • A (Aa dependence) • s • Experimentally very difficult: • J/Y ℓ+ ℓ- low rate, large combinatorial background •   ℓ+ ℓ- even lower rate (1/1000) , small background • c J/Y + g g is soft, low rate and large background • b  + g no comments Quarkonium physics: experimentally difficult, systematic study in various systems and energies

6. Experiments • CERN/SPS s ~ 19 GeV : • NA38/NA50 J/Y m+ m- pp, pA, AA • high rate, large statistics, large systematics • Helios • short program only • BNL/RHIC s = 20-200 GeV : • PHENIX • J/Y & m+ m- (forward) and J/Y & e+e- (central) • high rate, moderate acceptance  large statistics • central detector: |h| < 0.35, Df=p and pT > 0.2 GeV/c • forward arm: 1.2 < |h| < 2.2 and pTOT > 2.0 GeV/c • STAR • J/Y e+ e- (midrapidity) • low rate, large acceptance  moderate statistics • |h| < 1.5 , Df=2p and pT > 0.2 GeV/c

7. Experimental Data CERN/SPS RHIC program completed much more to come …

8. Where will we be in 4,5,6 years ? • Depends very much on the driving force of the onium program PHENIX • and on: • run time, luminosity • trigger performance PHENIX fast simulator Nbin scaling etrigger=100% • Combined coverage: • |y|<0.35 for ee • 1.2 < y < 2.4 for mm • fast: 25 kHz L1 acceptance rate • (40 x Lnominal = 56kHz) • Muon arm: • J/Y resolution dominated by MS •  resolution dominated by position resolution •  major project to improve • Central arm: 5-8 times lower rate but allow to separate 

9. What’s left to learn ? •  1S/2S/3S (separated) over broad range in xF (pA) • data from pA (E772) low statistics, small xF coverage • J/Y polarization • important in discriminating octet from singlet model • needs full azimuthal coverage • c J/Y + g • (c )/ (J/)  0.40 • B  J/Y + X • High precision inner tracking (Si) ct=462 mm • D – D correlations • y correlations (balance function)

10. Acceptance • In order to get qualitatively better results •  large acceptance (|y| < 1 – 1.5) • rate ~ acceptance for high pt • ~ acceptance2 for low pt Detector independent simulations: Note: the p cut is crucial and can only be relaxed if hadron rejection (e/h) is sufficiently large p cut  mY/

11. 92 MeV 258 MeV 173 MeV 100 MeV 193 MeV 285 MeV Resolution: Calorimetry - J/Y dE/E = 5%/E dE/E = 15%/E dE/E = 10%/E Very well separated peaks ~6s With ~2.3s separation y’ is lost Can distinguish peaks ~3.4s

12. Resolution: Calorimetry -  dE/E = 10%/E dE/E = 15%/E 305 MeV Not much better. ~1.8s 1s-2s ~0.7s 2s-3s 311 MeV 450 MeV 321 MeV 461 MeV 477 MeV dE/E = 5%/E 163 MeV All peaks are merged. ~1.25s 1s-2s ~0.49s 2s-3s 167 MeV ’’ is still lost. ~3.5s 1s-2s ~1.3s 2s-3s 172 MeV

13. 235 GeV 259 MeV 276 MeV Resolution: Tracking -  Peaks at CDF CDF  m+ m- Tracking chamber in 1.4 T field resolution 8.5 ‰ @ 4.9 GeV Hadronic background reduction factor ~10 MC: resolution 3% @ 6 GeV PRL 75 (1995) 4358

14. Quarkonia Cross-Section in pp at s = 200 GeV • Numbers in blue are derived quantities • BR are for e+e-unless not measured or with large errors in which case the m+m-values are taken

15. Quarkonia Rates in Au+Au at s = 200 GeV • RHIC II: • L = RHIC I  40 = 0.2 mb-1 s-1  40 = 8 mb-1 s-1 • Minimum bias interaction rate: 7200 mb 8 mb-1 s-1 = 58 kHz (1/17 ms) • One “nominal” RHIC year: 107s  Ldt = 80 nb-1 • R = L· ·BR(e+e-) ·fAB (fAB = 1 for minimum bias) • Rates into e+e- for 4p, 100% detector acceptance and efficiency

16. Summary • Lots of interesting onium physics left for the future • pp, pA: to study production mechanism and ‘normal’ absorption • pp, pA: c, b • pA + AA: polarization, P states, c, B  J/Y + X • AA: good statistics on separated  states • and new results open always new questions … • This requires • high rates (no slow-drift detector), trigger rate (EMC) ~ 50kHz • at mid-rapidity: • |h| < 1 • good tracking with ~1% @ 5 GeV ( high field) • good hadron rejection (probably EMC not enough) • granular EMC, or very high field to sweep away soft hadrons (c J/Y + g) • in forward region: • sorry, have not thought about that yet (tricky) Onium physics alone does not motivate a ‘new’ detector but it certainly can play an important role in the design of one.