160 likes | 255 Vues
This paper discusses the significance of quarkonium, related challenges, experimental advancements, and remaining mysteries in heavy quark potential and physics. It explores the suppression of J/Ψ by QGP and color screening effects. The text delves into experiments like NA38/NA50 at CERN/SPS and PHENIX and STAR at BNL/RHIC, highlighting data, problems, and future directions. Topics include J/Ψ production mechanisms, absorption phenomena, quarkonia suppression variations, and the need for comprehensive studies across different systems and energies for better insights. The article also addresses technical aspects like detector requirements, resolutions, and acceptance criteria for efficient data collection in heavy quark physics research.
E N D
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
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)
(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
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
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
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
Experimental Data CERN/SPS RHIC program completed much more to come …
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
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)
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/
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
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
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
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
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
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.