1. STAR HBT 4 oct 2002malisa - seminar IUCF1 Two-particle correlations and Heavy Ion Collision Dynamics at RHIC/STAR Mike Lisa, Ohio State University STAR Collaboration Motivation / STAR Central collision dynamics – spectra & HBT(p T ) Non-central collision dynamics – elliptic flow & HBT(  ) Further info from correlations of non-identical particles Consistent picture of RHIC dynamics Conclusions

2. STAR HBT 4 oct 2002malisa - seminar IUCF2 Why heavy ion collisions? Study bulk properties of nuclear matter The “little bang” Extreme conditions (high density/temperature) expect a transition to new phase of matter… Quark-Gluon Plasma (QGP) partons are relevant degrees of freedom over large length scales (deconfined state) believed to define universe until ~  s Heavy ion collisions ( “little bang”) the only way to experimentally probe deconfined state Study of QGP crucial to understanding QCD low-q (nonperturbative) behaviour confinement (defining property of QCD) nature of phase transition

3. STAR HBT 4 oct 2002malisa - seminar IUCF3 RHIC BRAHMS PHOBOS PHENIX STAR AGS TANDEMS Relativistic Heavy Ion Collider (RHIC) 2:00 o’clock 4:00 o’clock 6:00 o’clock 8:00 o’clock 10:00 o’clock STAR PHENIX RHIC AGS LINAC BOOSTER TANDEMS 9 GeV/u Q = +79 1 MeV/u Q = +32 HEP/NP  g-2 U-line BAF (NASA) PHOBOS 12:00 o’clock BRAHMS 2 concentric rings of 1740 superconducting magnets 3.8 km circumference counter-rotating beams of ions from p to Au max center-of-mass energy: AuAu 200 GeV, pp 500 GeV RHIC Runs Run I:Au+Au at  s = 130 GeV Run II: Au+Au and pp at  s = 200 GeV

4. STAR HBT 4 oct 2002malisa - seminar IUCF4 The STAR Collaboration 451 Collaborators (294 authors) 45 Institutions 9 Countries: Brazil, China, England, France, Germany, India, Poland, Russia, US

5. STAR HBT 4 oct 2002malisa - seminar IUCF5 Geometry of STAR ZCal Barrel EM Calorimeter Endcap Calorimeter Magnet Coils TPC Endcap & MWPC ZCal FTPCs Vertex Position Detectors Central Trigger Barrel or TOF Time Projection Chamber Silicon Vertex Tracker RICH

6. STAR HBT 4 oct 2002malisa - seminar IUCF6 Au on Au Event at CM Energy ~ 130 AGeV Event Taken June 25, 2000.

7. STAR HBT 4 oct 2002malisa - seminar IUCF7 Particle ID in STAR pions kaons protons deuterons electrons STAR dE/dx dE/dx PID range:  (dE/dx) =.08] p  ~ 0.7 GeV/c for K /   ~ 1.0 GeV/c for  p/p RICH PID range: 1 - 3 GeV/c for K /  1.5 - 5 GeV/c for  p/p RICH “kinks”: K     + VoVo Decay vertices K s   + +  -   p +  -   p +  +  -   +  -   +  +  +    + K - Topology Combinatorics K s   + +  -   K + + K -   p +  -   p +  +    + +  -   p +  -   from K + K - pairs K + K - pairs m inv same event dist. mixed event dist. background subtracted dn/dm

8. STAR HBT 4 oct 2002malisa - seminar IUCF8 Kaon Spectra at Mid-rapidity vs Centrality Exponential fits to m T spectra: K+K+ K-K- (K + +K - )/2 KsKs STAR preliminary 0-6% 11-18% 26-34% 45-58% 58-85% Centrality cuts 0-6% 11-18% 26-34% 45-58% 58-85% Centrality cuts 0-6% 11-18% 26-34% 45-58% 58-85% Centrality cuts Good agreement between different PID methods

9. STAR HBT 4 oct 2002malisa - seminar IUCF9 Hadrochemistry: particle yields vs statistical models

10. STAR HBT 4 oct 2002malisa - seminar IUCF10 lattice QCD applies

11. STAR HBT 4 oct 2002malisa - seminar IUCF11 Already producing QGP at lower energy? Thermal model fits to particle yields (including strangeness, J/  )  approach QGP at CERN? is the system really thermal? warning: e + e - falls on similar line!! dynamical signatures? (no) what was pressure generated? what is Equation of State of strongly-interacting matter? Must go beyond chemistry:  study dynamics of system well into deconfined phase (RHIC) lattice QCD applies

12. STAR HBT 4 oct 2002malisa - seminar IUCF12 Collision dynamics - several timescales initial state pre-equilibrium QGP and hydrodynamic expansion hadronic phase and freeze-out Chemical freeze out Kinetic freeze out “end result” looks very similar whether a QGP was formed or not!!! low-p T hadronic observables hadronization 1 fm/c ?5 fm/c ?10 fm/c ?50 fm/c ?time dN/dt “temperature”

13. STAR HBT 4 oct 2002malisa - seminar IUCF13 First RHIC spectra - an explosive source data: STAR, PHENIX, QM01 model: P. Kolb, U. Heinz various experiments agree well different spectral shapes for particles of differing mass  strong collective radial flow mTmT 1/m T dN/dm T light heavy T purely thermal source explosive source T,  mTmT 1/m T dN/dm T light heavy very good agreement with hydrodynamic prediction

14. STAR HBT 4 oct 2002malisa - seminar IUCF14 Hydrodynamics: modeling high-density scenarios Assumes local thermal equilibrium (zero mean-free-path limit) and solves equations of motion for fluid elements (not particles) Equations given by continuity, conservation laws, and Equation of State (EOS) EOS relates quantities like pressure, temperature, chemical potential, volume –direct access to underlying physics Works qualitatively at lower energy but always overpredicts collective effects - infinite scattering limit not valid there –RHIC is first time hydro works! lattice QCD input

15. STAR HBT 4 oct 2002malisa - seminar IUCF15 “Blast wave” Thermal motion superimposed on radial flow (+ geometry) Hydro-inspired “blast-wave” thermal freeze-out fits to , K, p,   R  s E.Schnedermann et al, PRC48 (1993) 2462 T th = 107 MeV  = 0.55 preliminary M. Kaneta

16. STAR HBT 4 oct 2002malisa - seminar IUCF16 Momentum-space characteristics of freeze-out appear well understood Coordinate-space ? Probe with two-particle intensity interferometry (“HBT”) The other half of the story…

17. STAR HBT 4 oct 2002malisa - seminar IUCF17 “HBT 101” - probing source geometry Measurable! F.T. of pion source 5 fm 1 m  source  (x) r1r1 r2r2 x1x1 x2x2 p1p1 p2p2 1-particle probability  (x,p) = U * U 2-particle probability

18. STAR HBT 4 oct 2002malisa - seminar IUCF18 “HBT 101” - probing the timescale of emission KK R out R side Decompose q into components: q Long : in beam direction q Out : in direction of transverse momentum q Side :  q Long & q Out (beam is into board) beware this “helpful” mnemonic!

19. STAR HBT 4 oct 2002malisa - seminar IUCF19 Large lifetime - a favorite signal of “new” physics at RHIC hadronization time (burning log) will increase emission timescale (“lifetime”) magnitude of predicted effect depends strongly on nature of transition measurements at lower energies (SPS, AGS) observe  <~3 fm/c “”“” with transition cc Rischke & Gyulassy NPA 608, 479 (1996) 3D 1-fluid Hydrodynamics  ~ …but lifetime determination is complicated by other factors…

20. STAR HBT 4 oct 2002malisa - seminar IUCF20 First HBT data at RHIC STAR Collab., PRL 87 082301 (2001) Data well-fit by Gaussian parametrization Coulomb-corrected (5 fm full Coulomb-wave) “raw” correlation function projection 1D projections of 3D correlation function integrated over 35 MeV/cin unplotted components

21. STAR HBT 4 oct 2002malisa - seminar IUCF21 HBT excitation function STAR Collab., PRL 87 082301 (2001) decreasing parameter partially due to resonances saturation in radii geometric or dynamic (thermal/flow) saturation the “action” is ~ 10 GeV (!) no jump in effective lifetime NO predicted Ro/Rs increase (theorists: data must be wrong) Lower energy running needed!? midrapidity, low p T  - from central AuAu/PbPb

22. STAR HBT 4 oct 2002malisa - seminar IUCF22 Central collision dynamics @ RHIC Hydrodynamics reproduces p-space aspects of particle emission up to p T ~2GeV/c (99% of particles)  hopes of exploring the early, dense stage Heinz & Kolb, hep-th/0204061

23. STAR HBT 4 oct 2002malisa - seminar IUCF23 Central collision dynamics @ RHIC Hydrodynamics reproduces p-space aspects of particle emission up to p T ~2GeV/c (99% of particles)  hopes of exploring the early, dense stage x-space is poorly reproduced model source is too small and lives too long and disintegrates too slowly? Correct dynamics signatures with wrong space-time dynamics? The RHIC HBT Puzzle Heinz & Kolb, hep-th/0204061 Is there any consistent way to understand the data? Try to understand in simplest way possible

24. STAR HBT 4 oct 2002malisa - seminar IUCF24 Blastwave parameterization: Implications for HBT: radii vs p T Assuming , T obtained from spectra fits  strong x-p correlations, affecting R O, R S differently p T =0.2 p T =0.4 K K RSRS RORO “whole source” not viewed

25. STAR HBT 4 oct 2002malisa - seminar IUCF25 Blastwave: radii vs p T STAR data blastwave: R=13.5 fm,  freezeout =1.5 fm/c Using flow and temperature from spectra, can account for observed drop in HBT radii via x-p correlations, and R o <R s …but emission duration must be small Four parameters affect HBT radii p T =0.4 p T =0.2 K K

26. STAR HBT 4 oct 2002malisa - seminar IUCF26 From R long :  t kinetic  = 8-10 fm/c (fast!) Simple Sinyukov formula –R L 2 =  t kinetic  2 T/m T  t kinetic  = 10 fm/c (T=110 MeV) B. Tomasik (~3D blast wave) –  t kinetic  = 8-9 fm/c

27. STAR HBT 4 oct 2002malisa - seminar IUCF27 hydro evolution Dynamical models: x-anisotropy in entrance channel  p-space anisotropy at freezeout magnitude depends on system response to pressure Noncentral collision dynamics or

28. STAR HBT 4 oct 2002malisa - seminar IUCF28 hydro evolution Dynamical models: x-anisotropy in entrance channel  p-space anisotropy at freezeout magnitude depends on system response to pressure Noncentral collision dynamics hydro reproduces v 2 (p T,m) (details!) @ RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Heinz & Kolb, hep-ph/0111075

29. STAR HBT 4 oct 2002malisa - seminar IUCF29 hydro evolution later hadronic stage? hydro reproduces v 2 (p T,m) (details!) @ RHIC for p T < ~1.0 GeV/c system response  EoS early thermalization indicated Effect of dilute stage dilute hadronic stage (RQMD): little effect on v 2 @ RHIC Teaney, Lauret, & Shuryak, nucl-th/0110037 SPS RHIC

30. STAR HBT 4 oct 2002malisa - seminar IUCF30 hydro evolution later hadronic stage? hydro reproduces v 2 (p T,m) (details!) @ RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Effect of dilute stage dilute hadronic stage (RQMD): little effect on v 2 @ RHIC significant (bad) effect on HBT radii calculation: Soff, Bass, Dumitru, PRL 2001 STAR PHENIX hydro only hydro+hadronic rescatt

31. STAR HBT 4 oct 2002malisa - seminar IUCF31 hydro evolution later hadronic stage? hydro reproduces v 2 (p T,m) (details!) @ RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Effect of dilute stage dilute hadronic stage (RQMD): little effect on v 2 @ RHIC significant (bad) effect on HBT radii related to timescale? - need more info Teaney, Lauret, & Shuryak, nucl-th/0110037

32. STAR HBT 4 oct 2002malisa - seminar IUCF32 hydro evolution later hadronic stage? hydro reproduces v 2 (p T,m) (details!) @ RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Effect of dilute stage dilute hadronic stage (RQMD): little effect on v 2 @ RHIC significant (bad) effect on HBT radii related to timescale? - need more info qualitative change of freezeout shape!! important piece of the puzzle! in-plane- extended out-of-plane-extended Teaney, Lauret, & Shuryak, nucl-th/0110037

33. STAR HBT 4 oct 2002malisa - seminar IUCF33 Possible to “see” via HBT relative to reaction plane?  p =0°  p =90° R side (large) R side (small) for out-of-plane-extended source, expect large R side at 0  small R side at 90  2 nd -order oscillation R s 2 [no flow expectation] pp

34. STAR HBT 4 oct 2002malisa - seminar IUCF34 “Traditional HBT” - cylindrical sources (reminder) KK R out R side Decompose q into components: q Long : in beam direction q Out : in direction of transverse momentum q Side :  q Long & q Out (beam is into board)

35. STAR HBT 4 oct 2002malisa - seminar IUCF35 Anisotropic sources  Six HBT radii vs  Source in b-fixed system: (x,y,z) Space/time entangled in pair system (x O,x S,x L ) out pp b KK side x y ! explicit and implicit (x  x (  )) dependence on  Wiedemann, PRC57 266 (1998).

36. STAR HBT 4 oct 2002malisa - seminar IUCF36 Symmetries of the emission function I. Mirror reflection symmetry w.r.t. reactionplane (for spherical nuclei):  with II. Point reflection symmetry w.r.t. collision center (equal nuclei):  with Heinz, Hummel, MAL, Wiedemann, nucl-th/0207003

37. STAR HBT 4 oct 2002malisa - seminar IUCF37 Fourier expansion of HBT radii @ Y=0 Insert symmetry constraints of spatial correlation tensor into Wiedemann relations and combine with explicit  -dependence: Note: These most general forms of the Fourier expansions for the HBT radii are preserved when averaging the correlation function over a finite, symmetric window around Y=0. Relations between the Fourier coefficients reveal interplay between flow and geometry, and can help disentangle space and time Heinz, Hummel, MAL, Wiedemann, nucl-th/0207003

38. STAR HBT 4 oct 2002malisa - seminar IUCF38 x out x side K Anisotropic HBT results @ AGS (  s~2 AGeV)  p (°) 0180 0 0 0 10 -10 20 40 R 2 (fm 2 ) outsidelong ol os sl Au+Au 2 AGeV; E895, PLB 496 1 (2000) strong oscillations observed lines: predictions for static (tilted) out-of-plane extended source  consistent with initial overlap geometry  p = 0°

39. STAR HBT 4 oct 2002malisa - seminar IUCF39 x out x side K Meaning of R o 2 (  ) and R s 2 (  ) are clear What about R os 2 (  ) ?  p (°) 0180 0 0 0 10 -10 20 40 R 2 (fm 2 ) outsidelong ol os sl Au+Au 2 AGeV; E895, PLB 496 1 (2000) R os 2 (  ) quantifies correlation between x out and x side No correlation (tilt) b/t between x out and x side at  p =0° (or 90°) K x out x side K x out x side K x out x side K x out x side K x out x side K x out x side  p = 0°  p ~45° Strong (positive) correlation when  p =45° Phase of R os 2 (  ) oscillation reveals orientation of extended source No access to 1 st -order oscillations in STAR Y1

40. STAR HBT 4 oct 2002malisa - seminar IUCF40 Indirect indications of x-space anisotropy @ RHIC v 2 (p T,m) globally well-fit by hydro-inspired “blast-wave” (Houvinen et al) STAR, PRL 87 182301 (2001) soliddashed 0.04  0.010.09  0.02  a (c) 0.04  0.01 0.0S2S2 0.54  0.030.52  0.02  0 (c) 100  24135  20 T (MeV) temperature, radial flow consistent with fits to spectra anisotropy of flow boost spatial anisotropy (out-of-plane extended) 

41. STAR HBT 4 oct 2002malisa - seminar IUCF41 STAR data Au+Au 130 GeV minbias preliminary significant oscillations observed blastwave with ~ same parameters as used to describe spectra & v 2 (p T,m) additional parameters: R = 11 fm  = 2 fm/c !! full blastwave consistent with R(p T ), K- 

42. STAR HBT 4 oct 2002malisa - seminar IUCF42 preliminary full blastwave STAR data Au+Au 130 GeV minbias significant oscillations observed blastwave with ~ same parameters as used to describe spectra & v 2 (p T,m) additional parameters: R = 11 fm  = 2 fm/c !! consistent with R(p T ), K-  no spatial anisotropy no flow anisotropy both flow anisotropy and source shape contribute to oscillations, but… geometry dominates dynamics freezeout source out-of-plane extended  fast freeze-out timescale ! (7-9 fm/c)

43. STAR HBT 4 oct 2002malisa - seminar IUCF43 Azimuthal HBT: hydro predictions RHIC (T 0 =340 MeV @  0 =0.6 fm) Out-of-plane-extended source (but flips with hadronic afterburner) flow & geometry work together to produce HBT oscillations oscillations stable with K T Heinz & Kolb, hep-th/0204061 (note: R O /R S puzzle persists)

44. STAR HBT 4 oct 2002malisa - seminar IUCF44 Azimuthal HBT: hydro predictions “LHC” (T 0 =2.0 GeV @  0 =0.1 fm) In-plane-extended source (!) HBT oscillations reflect competition between geometry, flow low K T : geometry high K T : flow sign flip RHIC (T 0 =340 MeV @  0 =0.6 fm) Out-of-plane-extended source (but flips with hadronic afterburner) flow & geometry work together to produce HBT oscillations oscillations stable with K T Heinz & Kolb, hep-th/0204061

45. STAR HBT 4 oct 2002malisa - seminar IUCF45 HBT( φ ) Results – 200 GeV Oscillations similar to those measured @ 130GeV 20x more statistics  explore systematics in centrality, k T much more to come… STAR PRELIMINARY

46. STAR HBT 4 oct 2002malisa - seminar IUCF46 Kaon – pion correlations: dominated by Coulomb interaction Smaller source  stronger (anti)correlation K-p correlation well-described by: Blast wave with same parameters as spectra, HBT But with non-identical particles, we can access more information… STAR preliminary Adam Kiesel, Fabrice Retiere

47. STAR HBT 4 oct 2002malisa - seminar IUCF47 Initial idea: probing emission-time ordering Catching up: cos  0 long interaction time strong correlation Ratio of both scenarios allow quantitative study of the emission asymmetry Moving away: cos  0 short interaction time weak correlation Crucial point: kaon begins farther in “out” direction (in this case due to time-ordering) purple K emitted first green  is faster purple K emitted first green  is slower

48. STAR HBT 4 oct 2002malisa - seminar IUCF48 measured K-  correlations - natural consequence of space-momentum correlations clear space-time asymmetry observed C+/C- ratio described by: –“standard” blastwave w/ no time shift Direct proof of radial flow-induced space-momentum correlations Kaon = 0.42 GeV/c Pion = 0.12 GeV/c STAR preliminary

49. STAR HBT 4 oct 2002malisa - seminar IUCF49 Summary RHIC 130 GeV Au+Au Disclaimer: all numbers (especially time) are rough estimates Tomasik (3D blastwave): 8-9 fm/c (fit to PHENIX even smaller) Sinyukov formula: R long 2 =  2 T/m T = 10 fm/c for T=110 MeV K-  K*

50. STAR HBT 4 oct 2002malisa - seminar IUCF50 Summary RHI – the only way to create/study deconfined colored matter Hadrochemistry suggests creation of QGP @ RHIC (and SPS) Quantitative understanding of bulk dynamics crucial to extracting real physics at RHIC p-space - measurements well-reproduced by models anisotropy [v 2 (p T,m)]  system response to compression (EoS) x-space - generally not well-reproduced anisotropy [HBT(  )]  evolution, timescale information, geometry/flow interplay Azimuthally-sensitive HBT: correlating quantum correlation with bulk correlation reconstruction of full 3D source geometry relevant here: OOP freeze-out Data do suggest consistent (though surprising) scenario strong collective effects rapid evolution, then emission in a “flash” (key input to models) where is the hadronic phase? K- , HBT(p T ), HBT(  ), K*… By combining several (novel) measurements, STAR severely challenges our understanding of dynamics in the soft sector of RHIC

51. STAR HBT 4 oct 2002malisa - seminar IUCF51 Backup slides follow Freezeout geometry out-of-plane extended early (and fast) particle emission ! consistent with blast-wave parameterization of v 2 (p T,m), spectra, R(p T ), K-  With more detailed information, “RHIC HBT puzzle” deepens what about hadronic rescattering stage? - “must” occur, or…? does hydro reproduce  t  or not?? ~right source shape via oscillations, but misses R L (m T ) Models of bulk dynamics severely (over?)constrained

52. STAR HBT 4 oct 2002malisa - seminar IUCF52 Summary Freeze-out scenario f(x,t,p) crucial to understanding RHIC physics p-space - measurements well-reproduced by models anisotropy  system response to compression probe via v 2 (p T,m) x-space - generally not well-reproduced anisotropy  evolution, timescale information Azimuthally-sensitive HBT: a unique new tool to probe crucial information from a new angle  elliptic flow data suggest x-space anisotropy  HBT R(  ) confirm out-of-plane extended source for RHIC conditions, geometry dominates dynamical effects oscillations consistent with freeze-out directly from hydro stage (???) consistent description of v 2 (p T,m) and R(  ) in blastwave parameterization challenge/feedback for “real” physical models of collision dynamics

53. STAR HBT 4 oct 2002malisa - seminar IUCF53 RHIC  AGS Current experimental access only to second-order event-plane odd-order oscillations in  p are invisible cannot (unambiguously) extract tilt (which is likely tiny anyhow) cross-terms R sl 2 and R ol 2 vanish @ y=0  concentrate on “purely transverse” radii R o 2, R s 2, R os 2 Strong pion flow  cannot ignore space-momentum correlations (unknown) implicit  -dependences in homogeneity lengths  geometrical inferences will be more model-dependent the source you view depends on the viewing angle

54. STAR HBT 4 oct 2002malisa - seminar IUCF54 Summary of anisotropic shape @ AGS RQMD reproduces data better in “cascade” mode Exactly the opposite trend as seen in flow (p-space anisotropy) Combined measurement much more stringent test of flow dynamics!!