The sQGP at RHIC: Recent Results and New Possibilities

1. The sQGP at RHIC: Recent Results and New Possibilities Richard Seto University of California, Riverside Jyvaskyla, Finland April 28, 2006

2. Properties of Medium What we know: RHIC • What we know • System appears thermally and chemically equilibrated • This happens early <2 fm/c • Energy density high >10 GeV/fm3 • parton energy loss is large • viscosity/entropy, η/s is low ( conjecture ~1/4π?) • DOF ~ “quasi-quarks” • General picture is stable since ~ 2004 • More data since QM 2005 • More theory • A clearer view

3. Busy days at RHIC p+p d+Au Au+Au Cu+Cu 22.4 GeV ? 62.4 GeV 130 GeV 200 GeV Run 1 - 3 Run 4 - 5 Run 6 4 experiments – BRAHMS, PHENIX, PHOBOS, STAR

4. 100 Cross over (wanna be 1st order) 4 5 10 ~Energy Density (GeV/fm3) Partonic 0.1 1 10 0.1 ~Time (fm) A cartoon – the life history of the sQGP CGC “glasma” T. Lappi hard probes Thermalization Strongly Interacting Elliptic flow Recombination ~some reinteraction L. McLerran (modified by R.S.)

5. energy density“jet” energy loss hard probles energy loss

6. What is the energy density? “Jet quenching” AuAu 200 GeV direct photons scale as Ncoll π0suppressed hadron suppression shows quenching independent of identity of produced hadron Direct γ • Calculations: • dNg/dy ~ 1000 • Wicks et al, nucl-th/0512076 • ε ~10-15 GeV/fm3 • εcritial ~0.6 GeV/fm3 π0 η RAA

7. System dependenceAu+Au and Cu+Cu sNN = 200 GeV

8. Au+Au and Cu+Cu sNN = 200 GeV RAA Function of Npart independent of system

9. light (M.DjordjevicPRL 94 (2004)) How is the energy lost? • The sQGP has enormous stopping power • rifle bullet stopped in a tissue • Original idea – energy loss by gluon radiation • In 2001, Dokshitzer and Kharzeev showed “dead cone” effect  charm quark small energy loss

10. What about heavy quarks? (electrons from c and b) (1) q_hat = 0 GeV2/fm (4) dNg /dy = 1000 (2) q_hat = 4 GeV2/fm (3) q_hat = 14 GeV2/fm Theory curves (1-3) from N. Armesto, et al., PRD 71, 054027 (4) from M. Djordjevic, M. Gyullasy, S.Wicks, PRL 94, 112301 • Charm high pT suppression is as strong as light hadrons!!! • Problem – difficult to reconcile with gluon radiative energy loss • theorists have to go back to the drawing board

11. Hadronization(so I can introduce recombination) reco

12. Recombination and the baryon anomaly pbar/π varies with √sNN in Cu+Cu PHENIX Preliminary • Originally thought: particle production at “moderate” pTfrom mini-jet Fragmentation pbar/π- ratio CuCu central At ISR pbar/π- ~ 0.2 higher energy 200 GeV BUT Heavy ion Collisions pbar/π- ~0.7 Increasing with energy 22 GeV

13. Baryon/meson (pbar/p-) at √s = 200 GeV AuAu • Scales with Npart independent of system at h=0 and 3.2

14. Explanation: Recombination • Naively: recombine quasi-partons (“quasiquarks” – Gavai) • PT • baryons pT  3 pT • mesons pT  2 pT • Problem: protons exhibit “jettiness” Mueller et al, Hwa et al, Ko et al +Thermal spectrum=Large pbar/π This implies that we begin in a “quasi-partonic” thermal system

15. STAR Preliminary STAR Preliminary ReCo Model Modification(Hwa) Premise: The production of Φ and Ω particles is almost exclusively from thermal strange quarks even out to 8 GeV/c Observables: The ratio of Ω/Φ yields should rise linearly with pT

16. Elliptic Flow (v2)ViscosityRecombination v2 v2

17. PHENIX Huovinen et al Previous Results • If system free streams • spatial anisotropy is lost • v2 is not developed • Hence • Early thermalization • low viscosity • detailed hydro calculations (QGP+mixed+RG, zero viscosity) • εtherm ~ 0.6 -1.0 fm/c • ε~15-25 GeV/fm3 • (ref: cold matter 0.16 GeV/fm3) (Teany et al, Huovinen et al)

18. Recombination and v21) Three regions of v2 v2 STAR preliminary v2 Maya Shimomura, SQM’06 from partonic quark number dependent from partonic AND hadronic mass dependent geometry-driven momentum anisotropy geometry-driven absorption anisotropy

19. 2) Data from minimum bias Au+Au collisions at sNN= 200 GeV PHENIX Preliminary (mT - m0)

20. 3) A recombination test rescale by quark number Au+Au collisions at √sNN= 200 GeV PHENIX Preliminary Recombination works! (mT - m0)

21. v2 of strange hadrons from STAR • Mass ordering observed at lower pT fit by hydro in hadronic phase • v2 saturates for pT > 3 GeV/c • Clear baryon/meson difference at intermediate to high pT observed • New, high statistics measurement shows deviation from ideal scaling • Mesons > 1 • Baryons<1 • Consistent with gluon-quark constituent models of recombination

22. v2 of strange hadrons from STAR • Mass ordering observed at lower pT fit by hydro in hadronic phase • v2 saturates for pT > 3 GeV/c • Clear baryon/meson difference at intermediate to high pT observed • New, high statistics measurement shows deviation from ideal scaling • Mesons > 1 • Baryons<1 • Consistent with gluon-quark constituent models of recombination

23. v2 of strange hadrons from STAR • Mass ordering observed at lower pT fit by hydro in hadronic phase • v2 saturates for pT > 3 GeV/c • Clear baryon/meson difference at intermediate to high pT observed • New, high statistics measurement shows deviation from ideal scaling • Mesons > 1 • Baryons<1 • Consistent with gluon-quark constituent models of recombination The same scaling behaviour is observed in62 GeV data

24. The  - a test • the  • mass ~ proton • quarks - meson V2 behaves as recombination says it should ALL hadrons seem to obey quark number scaling!

25. Hydro works in min-bias not as function of centrality initial cond? (Rafelski) Hydrodynamics (in the hadronic phase) and centrality

26. recombination and number of quark scaling works for centrality dependence Recombination and centrality? peripheral mid-central central Recombination works well. WHY? What is recombining?? DOF??? A quasi-quark Plasma? “constituent quarks”

27. DOF and Baryon-Strangeness Correlations • different degrees of freedom introduce different correlations between conserved charges • assumption: conservation of charge @ hadronization local in rapidity • introduce baryon-number strangeness correlation: • system of particles: • connection to Lattice susceptibilities: QP-QGP: CBS=1 HG: CBS~ 2/3 BS-QGP: CBS~0.61 CBS: V. Koch, A. Majumder & J. Randrup, PRL95 182301 (2005) BS-QGP: E. Shuryak, I. Zahed,PRC70 021901 (2004);PRD70 054507 (2004)

28. CBS & CQS: Lattice & Lessons • T>TC: CBS=1 • mesonic as well as baryonic bound-states ruled out via χBS • Lattice confirms quasi-quark nature of flavor carriers in the deconfined phase Gavai, Majumder Gavai & Gupta, PRD 73, 14006, 2006

29. v2 heavy quarks and viscosity The stone in the river or the concrete canoe University of Wisconsin Badgers engineer third-straight concrete canoe title

30. Flow, viscosity, and strong coupling • Conversion of spatial anisotropy to momentum anisotropy depends on viscosity • Same phenomena observed in gases of strongly interacting atoms (Li6) M. Gehm, et alScience 298 2179 (2002) strongly coupled viscosity~0 weakly coupled finite viscosity The RHIC fluid behaves like this, viscocity~0 now throw a stone in there

31. data prefers charm flow for charm to flow interactions must be very strong Viscosity small Heavy quarks: Single electron v2 Greco, Ko, Rapp PLB 595 (2004) 202

32. pT Hendrik, Greco, Rapp nucl-th/0508055 w.o. B meson (c flow) w. B meson (c,b flow) • based on quark coalescence model • c, b reso ; c,b get v2 by elastic scat. in QGP B meson contribution heavy quark electron v2 • B electron v2 reduces heavy quark electron v2 @ high pT • We need to directly measure D’s and B’s

33. Comment on a quantitative measure of the viscosity • Upgrades -microvertex detectors - to both STAR and PHENIX will allow measurement of D and B mesons directly • Theory – will take a while • Meanwhile – viscosity better become part of our ethos

34. Back to the beginningHow does the sQGP get started? a candidate - the CGC CGC

35. CGC • prediction: suppression in dAu collisions • forward • central for all particles Central Midcentral

36. What about charm? • prompt muons charm(bottom) are suppressed in dAu CGC Xiaorong Wang, SQM 2006 Au South Arm d Au d North Arm

37. Initial Temperature Tinitial

38. Compare to NLO pQCD • L.E.Gordon and W. Vogelsang • Phys. Rev. D48, 3136 (1993) • excess above pQCD Thermal photons - The Spectrum Compare to thermal model • D. d’Enterria, D. Perresounko • nucl-th/0503054 2+1 hydro T0ave=360 MeV(T0max=570 MeV) t0=0.15 fm/c • data above thermal at high pT Compare to thermal + pQCD • data consistent with thermal + pQCD The Future – PHENIX- HBD

39. What have we learned • Jet quenching • Charm quark energy loss, pretty well established • Viscosity • Charm flows – further evidence that viscosity is small (interactions are strong) • Recombination • baryon to meson ratio seems to obey recombination scaling • All particles seem seem to obey v2 recombination scaling. [, ;Ω] • Some evidence for fine structure • Evidence for quasi-partons from Recombination/Lattice • CGC • indications of charm suppression in dAu collisions at forward rapidity RHIC is now studying a state of matter clearly above the transition Question: So where is it? Deconfinement? Is there a critical point?

40. Deconfinement and Screening (a puzzle) Debye screening

41. A Theory update which bothers experimentalists • J/  “melts” at T>1.5 TC (Agnes Mocsy, Peter Petereczky) • “Screening likely not responsible for quarkonia suppression” (Agnes Mocsy, Peter Petereczky) • “You have to use the right potential” (CY Wong) • Does quarkonia suppression tell us anything about deconfinement!??? • Who is right?!! an experimentalist

42. Suppression similar in amount to SPS consistent with screening+ regeneration J/ suppression sum regeneration screening

43. 1.2<|y|<2.4 |y|<0.35 Aside: RAA of J/ in Au+Au/Cu+Cu • Most things depend on Npart independent of species • Why is J/ at y=0 different for Cu and Au? Corona? • Might help in understanding suppression mechanism Constrained by d+Au AuAu CuCu

44. <pT2> as a function of Ncol Au+Au = RED Cu+Cu = BLUE Dashed: without recombination Solid: includes recombination Recombination model matches better to the data... nucl-th/0505055

45. No recombination All recombination Recombination predictions vs rapidity • Recombination ( Thews et al., nucl-th/0505055 ) predicts a narrower rapidity distribution with an increasing Npart. • Going from p+p to the most central Au+Au : no significant change seen in the shape of the rapidity distribution. Central peripheral

46. RAA vs. pT in Au+Au/Cu+Cu • Suppression of J/ψ yield at low pT in both Au+Au and Cu+Cu. • High pT J/ψ escape the medium? Leakage effect? [Phys. Lett. B 607 (2005)] • Might one expect “pile up” at low pT for recombination+energy loss?

47. Questions • What is the energy loss mechanism for hard quarks? • Can we get a good measure of the initial temperature? • Chiral Symmetry? • Deconfinement? Any Clue? • Is the CGC really the initial state for the sQGP • Can we measure quantitatively the viscosity? • THEORY • More General Questions • Do we understand why the interaction is so strong? • Do we understand the DOF? Interplay of theory and experiment – very important both in the “CGC” and the “sQGP”

48. The Future RHIC II increase in Luminosity High L at lower energies- the critical point PHENIX- upgrades The Nosecone Calorimeter

49. What would we like to measure?

50. requires highest AA luminosity What would we like to measure? • What is the energy loss mechanism for hard quarks? • Jet tomography (high pT PID, jet-jet and g-jet) • Can we get a good measure of the initial temperature? • Chiral Symmetry? • Electromagnetic radiation (e+e- pair continuum, LMVM) • Deconfinement? Any Clue? • Quarkonium (J/, ’ , c and (1s),(2s),(3s)) • Is the CGC really the initial state for the sQGP • gluon saturation in nuclei (particle production at forward rapidity) • Can we measure quantitatively the viscosity? • Heavy flavor (c- and b-production) • What is the energy loss mechanism for hard quarks? • Jet tomography (high pT PID, jet-jet and g-jet) • Can we get a good measure of the initial temperature? • Chiral Symmetry? • Electromagnetic radiation (e+e- pair continuum, LMVM) • Deconfinement? Any Clue? • Quarkonium (J/, ’ , c and (1s),(2s),(3s)) • Is the CGC really the initial state for the sQGP • gluon saturation in nuclei (particle production at forward rapidity) • Can we measure quantitatively the viscosity? • Heavy flavor (c- and b-production)