J/ y as a signal of deconfinement

1. J/y as a signal of deconfinement Focus on J/y production results for p+p, d+Au, Au+Au and Cu+Cuat RHIC (next talk: results withfixed target). David Silvermyr, ORNL Critical Point and Onset of Deconfinement Firenze, July 4th 2006

2. Lattice QCD calculation V(r)/ r Heavy Quarkonia - Intro Lattice QCD results show that the confining potential between heavy quarks is screened at high temperature. This screening should suppress bound states such as J/y. However, recent lattice results indicate that the J/y spectral functions only show modest modification near the critical temperature, and thus may not be suppressed until higher T.

3. Original Signature: Matsui & Satz (’86 & ’06) SPIRES : 934 citations so far (June ’06)

4. An Unambiguous Signature? • Matsui and Satz carefully outlined the conditions that needed to be met for an observed suppression to be an unambiguous signature of QGP formation. • Focus on one of these assumptions - may well be violated. .

5. Competing J/ Production Effects • Normal nuclear absorption: J/ breakup by nucleons in the final state resulting in charm hadrons • Shadowing: Accounts for parton distribution modifications relative to free protons Affects parton distribution function before collision occurs • Color Screening: In deconfined medium resonance interactions needed to convert cc pairs to J/’s are prohibited • Comover Interactions: J/ interactions with secondary hadrons results in dissociation Suppression mechanism that does not require deconfined medium • Parton Induced Dissociation: Breakup of J/ due to in medium parton interactions • J/ Recombination: Regeneration of J/’s from off-diagonal c and c pairs • Feed-down effects, and more.. A complex story: the devil is in the details..

6. Observation at CERN SPS (NA50/60) J/y normalized to Drell-Yan vs “Centrality” N.B.: D-Y is not the optimal normalization, closed/open charm is better. • Pb+Pb collisions show suppression in excess of "normal" nuclear suppression • (Recent news: NA60 observed very similar trend in In+In collisions.) Expectation Suppression

7. T. Affolder et al., Phys. Rev. Lett. 85, 2886. F. Abe et al., Phys. Rev. Lett. 79, 572. CDF pp (s = 1.8 TeV) results • Color singlet model underpredicts high-pT yield. • Color octet model overpredicts transverse polarization at high pT.

8. J/y @ RHIC: Physics Plan • pp collisions • Reference, Initial production mechanism RHIC: can have same √sNN energy as pA and AA.. • pA (or dA) collisions • Shadowing • Initial state energy loss • Cold medium absorption • AA + Light ion collisions • Modify path length through medium • Most efficient way to dial in Ncoll,Npart • Energy scans • Modify energy density • More difficult (both luminosity & cross-sections fall quickly w/ energy) Many competing effects: - Reference data essential!

9. Charmonium and Beyond in STAR J/ Run5 pp STAR Preliminary J. Gonzalez, SQM06 STAR Preliminary J/ Run4 AuAu Dielectron Invariant Mass (GeV/c2) Dielectron Invariant Mass (GeV/c2) STAR AuAu preliminary Nice start with clear mass-peaks for AuAu and pp! [part of total dataset analyzed] Rest of talk: focus on PHENIX.

10. RHIC Scaling Law : J/y in PHENIX Order of magnitude improvements for approx. every two RHIC runs – quite remarkable (another factor 3 for pp from Run5 to Run6) ! Hope to see continued progress and success like this!

11. Start: p+p Reference • Consistent with trend of world’s data • ~Consistent with at least one COM (Color Octet Model) calculation [Factor x10, and x30 more statistics from Runs5 and 6] Phys. Rev. Lett. 96, 012304 (2006).

12. rapidity y X2 X1 J/ in South y < 0 Anti Shadowing Shadowing X1 X2 J/ in North y > 0 d+Au: Disentangle Cold Nuclear Effects South (y < -1.2) : via m+m- • large X2 (in gold) ~ 0.090 Central (y ~ 0) : via e+e- • intermediate X2 ~ 0.020 North (y > 1.2) : via m+m- • small X2 (in gold) ~ 0.003 • Gluon (anti-)shadowing • Nuclear absorption. • Initial state energy loss. • Cronin effect gluons in Pb / gluons in p X Eskola, et al., Nucl. Phys. A696 (2001) 729-746.

13. p-p J/Psi – PHENIX 200GeV R. Vogt: EKS98 shadowing. 3mb absorption X2 X1 J/ in South y < 0 Rapidity J/y rapidity distribution in p+p and d+Au Collisions Total cross section in p+p (nucl-ex/0507032): 2.61+/-0.20(fit)+/-0.26(abs) µb

14. 1.2 1.0 0.8 RdA 0.6 0.4 0.2 0 Rapidity and Ncoll Dependence of RdAu: Gluon Shadowing and Nuclear Absorption Rapidity • Data favor weak shadowing and weak nuclear absorption effect: Calc. with 1-3 mb most successful at describing the data. [Shape reminiscent to what’s seen for dNch/dh (e.g. PHOBOS)] • More suppression for more central events(?)

15. Phenix muon arm 1st Upsilons at RHIC ! RUN5 pp News PHENIX accumulated ~3pb-1 p+p collision during 2005 run. Will give order of magnitude stat. improvement for reference for d+Au and Au+Au. Different Quarkonia states test the degree of color screening and measure the temperature. Significant yields (>hundreds) at RHIC-II ? Beauty measurements will be quiteinteresting.

16. 0-20% 20-40% 40-93% Example Mass-plots: • Background subtracted using event mixing • Cu+Cu signal is similar to Au+Au peripheral, with much larger statistics Heavy Ions: J/ signal in Au+Au J/e+e- PHENIX J/-

17. J/ymm muon arm 1.2 < |y| < 2.2 J/yee Central arm -0.35 < y < 0.35 AuAu mm 200 GeV/c CuCu mm 200 GeV/c AuAu ee 200 GeV/c CuCu ee 200 GeV/c dAu mm 200 GeV/c CuCu mm 62 GeV/c RAA vs Ncoll(QM’05; nucl-ex/0510051) About a factor 3 suppression for most central Au+Au points Band around 1.0 refers to the uncertainty of the p+p reference. [and sometimes has a global sys. error added for the dataset in question..]

18. Results in A+A : vs cold nuclear matter effects AA AA suppression factor ~ 3 suppression factor ~ 3 1 mb 1 mb 3 mb 3 mb suppression factor ~ 2 suppression factor ~ 2 |y|~0 |y|~1.7 Observe a suppression of ~3 from pp and ( ~ factor 2) beyond cold nuclear effets. Note common error boxes now (post QM05) around individual points. .. Working on final results with reduced systematic errors ..

19. RHIC Cold Nuc Eff 1mb RHIC Cold Nuc Eff 1mb SPS sabs = 4.18 mb SPS sabs = 4.18 mb • Unclear if cold nuclear effects should be : • different (different suppression pattern) RHIC Cold Eff 3mb • or not (same suppression pattern) Au+Au and Cu+Cu results On the experimental point of view : Suppression at RHIC similar to suppression at SPS Although √s@RHIC=200 GeV and √s@SPS<20 GeV Need more precise measurement of cold nuclear effect at RHIC  need more dAu as well as AuAu data SPS normalized to NA51 p+p value (NA60 preliminary points from Arnaldi, QM05).

20. J/y : Suppression Models Some suppression models which reproduce NA50 data… AA … Overestimate the suppression at PHENIX Direct suppression in a hot medium : Cu+Cu Au+Au (Hadronic?) co-mover scattering

21. J/ Suppression in Heavy-ion Collisions May be Masked By Recombination Effects • In central Au+Au collision there are many (>10) c/c-bar pairs produced in a single event. • Calculations indicate that a significant number of J/’s could be produced by coalescing c and c-bar quarks that are the products of different hard scattering events. • This would have the effect of masking suppression due to the presence of a QGP.

22. Comparison with a prediction w. regeneration [After update from Rapp et al to use up-to-date charm and J/y p+p cross-sections:] agreement with data points slightly better than that of absorption calculation (with 3 mb sigma).

23. An alternative picture…

24. Phys.Lett. B561 (2003) 61-72 J/ Feeddown Effect • J/ yield is populated from both direct production and feeddown from the higher resonance states • Relative yield from each source experimentally found: • 60% direct production • 30% c feeddown • 10% ’ feeddown • Medium conditions determine whether each state exists in the bound form

25. Quarkonia production as a QGP thermometer • Even if jet suppression, flow results, etc. have already established that the medium created at RHIC is an sQGP, we would still like to establish its properties. • The quarkonium suppression pattern may be able to serve as a QGP thermometer. • In cartoon form… • It is argued that the common pattern seen at SPS and RHIC is due to complete suppression of ’ and c, which feeds down to create ~40% of the J/’s, and that the primordial J/’s aren’t suppressed at all by screening. H. Satz, J. Phys. G32, R25 (2006)

26. Copper-Copper 200 GeV J/y |y| = 1.2-2.2 CuCu: More Bins... • Rather smooth onset/scaling with centrality.. no distinct onset or plateau for cc suppression, with our preliminary data & errors

27. Test of Npart scaling Alternative looks at data may help to break gridlock.. Can the results be explained by some other scenario? Geometry and surface effects or scaling a la soft processes? [argued for NA50 data by e.g. Gazdzicki, Braun-Munzinger et al.]

28. More variables : Rapidity • Rapidity distribution of recombined J/y is supposed to be peaked at y=0 (e.g. R.L. Thews & al., nucl-th/0505055) • True IF charm distribution ~ J/y in p+p ! • But Au+Au charm rapidity distributions might be rather flat! off-diagonal (with recomb.) p+p data pQCD, adjust <kT2> diagonal

29. Invariant yield vs pt Cu+Cu (|y|[1.2,2.2]) Au+Au (|y|[1.2,2.2]) We fit the pt spectrum using to extract <pt2>

30. Mean transverse momentum vs Ncoll Recombination (Thews et al., nucl-th/0505055) predicts a narrower pT distribution, leading to a lower <pT²> Experimentally : data falls between the two hypotheses. Need to consider all datasets and error bars before drawing conclusions. Open markers : |y|<0.35 Solid markers : |y|~1.7 Open markers : |y|<0.35 Solid markers : |y|~1.7 p+pd+Au Cu+Cu No recombination No recombination Au+Au p+pd+Au With recombination With recombination Cronin / Broadening:

31. J/y Status RHIC data exhibits a factor 3 suppression for most central events in Au+Au collisions. Suppression vs Npart rather similar to what was seen at SPS. Comparison with models (here only used a subset..) suggests that 1) Models with only cold nuclear matter effects tend to under-predict the suppression 2) Models with color screening or comovers and without recombination have too much suppression 3) Models with recombination are in rather reasonable agreement with the data Not clear if recombination is the explanation though. Feed-downs suppressed? Mixed evidence for recombination from other variables: Con(?): The rapidity dependence of the J/ yield shows no dramatic change in shape with increasing Npart. Pro(?): <pT2> is also consistent with flat behaviour, but large error bars.

32. J/y Action Items • Need more work on data (in progress); reduce size of errors and go to final results. Using the statistically superior Run5 p+p dataset for reference should be helpful. It would be nice to confront theory with more precise results! :=) • Flow? - J/y v2 studies started; no results yet. Statistically very challenging analysis with existing RHIC datasets. Comparison between charm and charmonium should be instructive. • Question: Do we see (suppression + recombination) or just not so much suppression to start with..? • [‘soft’ scaling and similarity with NA50 suppression pattern - somewhat surprising and hard to overlook. Just coincidences?]

33. More data needed! • In any case (and as usual..), more data is needed.. • Need to study • Different quarkonia states (different melting points, different feeddown contributions). • Different collision energies • Modify charm quark density to change recombination fraction. • Modify temperature. • Better data vs. centrality, pT, y. • Polarization, J/-hadron correlations, flow (for production mechanism). • This physics is really just getting started at RHIC..

34. Run 6 200GeV p+p Invariant Mass (GeV/c2) Future Measurements: ’ With more luminosity we should be able to measure y’ in AuAu too!

35. Future Measurements: c PHENIX Run 5 200GeV p+p PHENIX Run 5 200GeV p+p (c - J/) Mass (GeV/c2) (c - J/) Mass (GeV/c2) Run 6 data set has a factor of x3 more luminosity. A very tough measurement in AuAu; dAu probably doable.

36. QM05 Exotica: More to Come Ultra-peripheral Collisions (UPC’s) • UPC’s : well calibrated • EM probe • measured by STAR • J/y by PHENIX

37. Future • Hopefully (PAC willing)…. • Run 7 & 8: high statistics Au+Au 200GeV, x10 luminosity • high statistics d+Au 200GeV, x10 luminosity And comparisons with STAR results! • Detector Upgrades : • Reaction Plane Detector (PHENIX, from Run-7) • Si Vertex Detector (PHENIX and STAR) • Nosecone Calorimeter, muon trigger upgrade, … • Longer term: • RHIC Upgrades: • Increased luminosity • Increased species Then there are also the LHC experiments soon, and the nice results from NA60 (next), so the upcoming few years should be really interesting!

38. Near-Term Future.. Let’s hope for some nice and friendly semi-final matches today and tomorrow (9 PM) !

39. Backup slides

40. Heavy quarkonium states, energy levels and radii Quarkonium – bound q/q-bar state

41. J/y transport model Adding QGP hydro and J/y transport  better agreement • Model includes : • Detailed QGP hydro • J/ψtransport • normal nuclear absorption: • σabs = 1 mb • σabs = 3 mb • (Curves for y=2 and y=0 are similar) Au+Au y~1.7|y| ~ 0 Zhu, Zhuang, Xu, PLB607 (2005) 107 + private communications

42. Sequential charmonium dissociation • Based on recent lattice QCD calculations, J/y melting temperature could be higher than initially expected  suppression of direct J/y could be out of the range of RHIC • On the other hand cc and y’ should melt at a temperature close to TC (~1.1 – 1.2 TC)  Anomalous suppression comes from cc and y’ feed-down. H. Satz, Hep-ph/0512217 Quarkonium dissociation temperatures – Digal, Karsch, Satz Karsch, Kharzeev and Satz, hep-ph/0512239 Overall J/y survival probability = measured/expected direct J/y survival probability assume to be 1 at SPS energy • J/y feed-down : • ~60% from direct production • ~30% cc J/y + g • ~10% y’  J/y + X Feed-down J/y survival probablity

43. Sequential charmonium dissociation Karsch, Kharzeev and Satz, hep-ph/0512239 SPS data • At SPS, NA50 measured : • J/y suppression • y’ suppression • but not cc NA60 preliminary (Lattice QCD  Sy’~Scc) Karsch, Kharzeev and Satz, hep-ph/0512239 SPS + RHIC data • At RHIC, PHENIX measured : • J/y suppression. data are consistent with sequential charmonium dissociation at both RHIC and SPS. Note: Systematic errors ignored.. 0.6 NA60 preliminary PHENIX preliminary More data needed

44. Suppression Mechanism • J/ Suppression Models: • assume heavy quarkonia are formed only during the initial hard nucleon-nucleon collisions • Subsequent interactions only result in additional loss of yield • Color Screening: • Color charge of one quark masked by the surrounding quarks • Prevents cc-bar binding in the interaction region • Characterized by Debye screening radius (rD) • If the screening radius is smaller than the J/ radius then the quarks are effectively masked from one another

45. RAA vs Npart : Comparison with NA50 data (QM’05) NA50 data is normalized to NA50 p+p point. Suppression level is rather similar between the two experiments, although the collision energy is 10+ times higher at RHIC (200 GeV vs 17 GeV). Note: size of error bars, or common systematic error band not negligible!

46. RAA vs Npart: Comparison with cold nuclear effects (QM05) Mid rapidity Forward rapidity Prediction from pQCD calculations, including 3mb nuclear absorption and shadowing. Seems to underestimate the suppression somewhat. Note: sabs somewhat too high wrt d+Au data; Should have 1 mb curve also.

47. RAA vs Npart: Comparison with predictions without regeneration (QM05) Models which approx. reproduce NA50 data, with J/ suppression only. (no regeneration mechanism) Over-estimates J/y suppression at RHIC!

48. RAA vs Npart : Comparison with predictions w. regeneration (QM05) Models using suppression + various regeneration mechanisms; Better matching with data points, but note that all model calculations should be checked to use up-to-date charm and J/y p+p cross-sections! (reduced exp. errors on those quantities would also help)

49. Central arms: hadrons, photons, electrons p > 0.2 GeV/c |y| < 0.35  Muon arms: muons at forward rapidity p > 2GeV/c 1.2 < |y| < 2.4  Centrality measurement: We use beam beam counters together with zero degree calorimeters Centrality is mapped to Npart (Ncol) using Glauber model The PHENIX detector J/e+e- J/m+m-

50. PHENIX p+p 200GeV PHENIX p+p 200GeV PHENIX Detector: Muon Arms • Muon Tracker and Muon Identifier provide good momentum resolution and tracking ability • High rate level 1 dimuon trigger • Online level 2 filtering Like Sign Subtraction