Marzia Rosati mrosati@iastate Iowa State University

1. Recent Measurements of Charmonium in Heavy Ion Collisions Marzia Rosati mrosati@iastate.edu Iowa State University Third Workshop on Quarkonium IHEP, Beijing China October 15, 2004

2. QGP SPS RHIC 4 energy density e/T4 LHC hadron gas TC ~ 170 MeV temperature Hunting the Quark Gluon Plasmaby Measuring Quarkonium Outline • New Quarkonium Measurements at SPS: NA60 • New Quarkonium Measurements at RHIC: PHENIX • Future Opportunities at RHIC and LHC

3. Charmonium as a Probe of QGP • Matsui and Satz predicted J/y production suppression in Quark Gluon Plasma because of color screening

4. The NA50 experiment A closed-geometrymuon spectrometer experiment

5. NA38/NA50 J/y suppression from p-A to Pb-Pb collisions • The J/y production is suppressed in Pb-Pb collisions with respect to the yields extrapolated from proton-nucleus data  anomalous suppression Measured / Expected ……… Lots of open questions  NA60

6. muon trigger and tracking magnetic field 7 In targets ZDC target boxwindows Beam tracker station Z-vertex of the interaction determined by the pixel telescope with ~ 200 µm accuracy Vertex transverse coordinates determined with better than 20 mm accuracy from the pixel telescope and beam tracker z-vertex (cm) hadron absorber Indium beam 158 A GeV NA60 What’s original in NA60: measuring dimuons in the target region silicon telescopein a 2.5 T dipole beam tracker targets

7. DY yield = 253± 161964 ± 126in range 2.9–4.5 GeV J/y yield = 35626 ± 361 J/y production in Indium-Indium collisions NA60 after muon track matching Background s(J/y) : 105  70 MeVmatching rate ~ 70% Charm J/y DY y’ A multi-step fit (max likelihood) is performed:a) M > 4.2 GeV : normalize the DY b) 2.2<M<2.5 GeV: normalize the charm (with DY fixed) c) 2.9<M<4.2 GeV: get the J/y yield (with DY & charm fixed)

8. all data rescaled to 158 GeV J/y / Drell-Yan in Indium-Indium collisions Projectile B s(J/y) / s(DY) = 19.6 ± 1.3for L = 6.8 fm or Npart = 128  0.85 ± 0.06w.r.t. the normal nuclear absorption J/y L Target preliminary NA60 L= mean length of the path of the (cc) system through nuclear matter

9. Event characterization detectors in middle Two central arms for measuring hadrons, photons and electrons Two forward arms for measuring muons J/yee in central arms electron measurement in range: ||  0.35 pe  0.2 GeV/c J/ymm: forward arms muon measurement in range: 1.2 < || < 2.4 pm 2 GeV/c PHENIX Detector

10. J/Y Measurement Planned at RHIC • p-p : study of production mechanism and cross sections • Color evaporation model, Color singlet model, Color octet model • Polarization, Rapidity dependence (electron and muon channels) • Production of J/, ',.. states • Base line for pA and AA • p(d)-A : study of "normal nuclear effects": shadowing and energy loss • Nuclear dependence of (J/): A or abs (nuclear absorption) • Base line for AA • A-A : study of "medium effect" in high density matter • J/ suppression : signature of QGP (Matsui/Satz) • J/ formation by c quark coalescence? • Comparisons between various collision species are very important. • Studies done via both dielectron and dimuon channels in PHENIX.

11. J/Y in Run 2 p-p Collisions +– Results consistent with shapes from various models and PDF. Take the PYTHIA shape to extract our cross-section Integrated cross-section : 234 ± 36 (stat) ± 34 (sys) ± 24(abs) μb e+e– Phys.Rev.Lett.92, 051802,2004

12. d-Au Collisions North Muon Arm South Muon Arm Eskola, Kolhinen, Vogt hep-ph/0104124 • PHENIX measurements cover different ranges of the Au parton momentum fraction where shadowing and anti-shadowing are expected • All expected to see pT broadening • dE/dx not expected to be significant effect at RHIC energies • Overall absorption expected Au d Central Arm PHENIX μ, North PHENIX m, SOUTH PHENIX e

13. +- ±± North Arm dAu 780 J/ψ’s  ~ 165 MeV J/Y in Run 3 d-Au Collisions In RUN3, we accumulated ~3nb-1 d-Au collisions. • combinatorial background is subtracted using the like-sign pairs • physical background (open charm/Drell-Yan) is fitted using an exponential

14. J/  +- High x2 ~ 0.09 Low x2 ~ 0.003 Cross section versus pT <pT2> = <pT2>dAu – <pT2>pp 1.77 ± 0.35 GeV2 1.29 ± 0.35 GeV2 (preliminary) J/  +- pT is broadened for dAu

15. dAu/pp versus pT Low x2 ~ 0.003 pT broadening comparable to lower energy (s = 39 GeV in E866) High x2 ~ 0.09

16. J/Y Rapidity Distribution in dAu and pp

17. compared to lower s Klein,Vogt, PRL 91:142301,2003 Kopeliovich, NP A696:669,2001 dAu/pp versus rapidity RdA Low x2 ~ 0.003 (shadowing region) • Data favors (weak) shadowing + (weak) absorption ( > 0.92) • With limited statistics difficult to disentangle nuclear effects. We will need another dAu run! (and more pp data also) 1st J/ψ’s at large negative rapidity!

18. Dy = 1.0 Coalescence model (Thews et al) Dy = 4.0 Stat. Model (Andronic et al.) Absorption model (Grandchamp et al.) Run2 AuAu Phys.Rev.C69, 014901,2004 • Disfavor models with enhancement relative to binary collision scaling. Cannot discriminate between models that lead to suppression relative to binary collision scaling.

19. Simple expectation for AuAu J/ψ’s based on nuclear dependence observed in dAu • Renormalize model predictions to dAu measurement (top panel). • Then reverse RdAu and multiply by itself (bottom panel) • Variations between models not too large at mid-rapidity, but substantial in the large negative or positive rapidity regions. Better models (physics understanding) might help, but a higher statistics dAu baseline, especially in the  regions is needed. • 2004 AuAu run: ~50 times more data (than RUN2) and we already see clear J/Y signals

20. Near future at RHIC • Full exploration of J/Y production versus “Nbinary” • Look forward to future runs with high luminosity where also studies for different collision species and with varying energy can be made • Upcoming run in December 2004 CuCu collisions and long p-p run

21. PHENIX Upgrade • Ultimately we want to detect open charm “directly” via displaced vertices • Development of required Si tracking for PHENIX well underway

22. RHIC-II Luminosity Upgrade • RHIC-II: • L = 5·1032 cm-2 s-1 (pp) • L = 7-9·1027 cm-2 s-1 = 7-9 mb-1 s-1 (AuAu) • hadr. min bias: 7200 mb 8 mb-1 s-1 = 58 kHz • 30 weeks, 50% efficiency  Ldt = 80 nb-1 • 100% reconstruction efficiency • Assume here: sAA = spp (AB)a • Au+Au, 30 weeks, 50% efficiency produced number of events • 2.7·108 J/Y • 1·107 Y’ • 170100 (1S) • 29700 (2S) • 32400 (3S)

23. dh The Physics Landscape: Pb+Pb Collisions SPS->RHIC->LHC Extrapolation of RHIC results favors low values

24. LHC Heavy Ions

25. Summary • The good and bad news: the phenomenology of charmonium in nuclear collisions is richer than anyone supposed • There is enough interesting physics to keep us busy • Things are not as simple as first supposed • The goal of the field has shifted from “discovering the quark-gluon plasma” to “characterizing the nuclear medium under extreme conditions” • This is a plus – we’ve moved past presupposing how things will behave and towards measuring and understanding what really happens • Charmonium is a critical probe in this wider effort • New data from RHIC and NA60 is right around the corner • Experimental program will continue at LHC