1. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO1  HBT in STAR Mike Lisa*, Ohio State University “Traditional” HBT results: 200 GeV vs 130 GeV Au+Au collisions New experimental developments Bowler/Sinyukov Coulomb correction Pushing the systematics – azimuthally-sensitive HBT Results from 130, 200 GeV Interpreting asHBT results Hydro, Hydro+RQMD, BlastWave Conclusions * Work of: Mercedes López-Noriega, Dan Magestro, Randy Wells

2. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO2 Reminder: p-space observables reproduced by dynamical models, x-space not Heinz & Kolb, hep-ph/0204061

3. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO3 “Standard” HBT:130 vs 200 GeV Essentially identical analysis carried out for 200 GeV data as published 130 GeV (exact centrality definition, etc, being finalized) New: centrality dependence of p T dependence mostly an overall scaling of R Little change with increased energy Transverse size slightly bigger @ low p T ? Similar p T -dependence R o /R s problem persists Longitudinal radius: no change Lower-energy RHIC run needed 130 GeV 200 GeV STAR, QM02

4. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO4 Recent analysis developments I RHIC analyses used “standard” Coulomb correction, used by previous experiments “apples-to-apples” extension of systematics Effects of “diluting” CC (resonances, etc) explored & reported @ QM01 R o affected most “Standard” Coulomb CC No Coulomb CC STAR, QM01; NPA698, 177c (2002) Y2 data: dilution effect vs p T, centrality R O /R S ~ 10-15% increase when f = ≈ 0.5 f More correct CC method of Bowler (’91) & Sinyukov (’98), used by CERES (’02) Similar effect on radii as dilution with f = In “right” direction, but does not solve R O /R S problem

5. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO5 “Traditional” HBT results ~ stable So what’s the problem with theory? –Timescale too long? –Hadronic phase overestimated? –HBT technique not understood? Can (HBT and other) data be consistently understood? –What are characteristics of freezeout source @ RHIC? Parameterization of freezeout Explore with further systematics– non-central collisions –Azimuthally-sensitive HBT

6. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO6 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

7. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO7 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

8. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO8 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

9. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO9 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

10. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO10 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

11. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO11 Indirect indications of x-space anisotropy @ RHIC v 2 (p T,m) globally well-fit by hydro-inspired “blast-wave” 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) 

12. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO12 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

13. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO13 Need a model of the freezeout- BlastWave BW: hydro-inspired parameterization of freezeout longitudinal direction infinite extent geometrically boost-invariant longitudinal flow Momentum space temperature T transverse rapidity boost coordinate space transverse extents R X, R Y RYRY RXRX freezeout in proper time  evolution duration  0 emission duration  7 parameters describing freezeout

14. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO14 BlastWave fits to published RHIC data p T spectra constrain (mostly) T,  0 (traditional) HBT constrains R,  0,  –(fit to STAR-HBT only) v 2 (p T,m) constrains  a, R X /R Y central midcentral peripheral CentralMidcentralPeripheral T (MeV) 108  3106  295  3 00 0.88  0.010.87  0.010.81  0.02 aa 0.06  0.010.05  0.010.04  0.01 R X (fm) 12.9  0.410.2  0.58.0  0.1 R Y (fm) 12.8  0.411.8  0.610.0  0.2  0 (fm/c)8.9  0.37.4  0.76.5  0.4  (fm/c)0.0  9.00.8  1.80.09  0.6  2 / ndf 80.5 / 101153.7 / 9274.3 / 68

15. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO15 “raw” after RP/binning correction preliminary flat within errors Significant (& “allowed”) oscillations observed in HBT radii RP/binning correction * significant produces R L 2 oscillation from “nowhere”? – is it real? Minbias observations at 130 GeV (*) [Heinz, Hummel, MAL, Wiedemann PRC 044903 (2002)] R. Wells, PhD thesis, Ohio State, 2002

16. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO16 Minbias asHBT well-reproduced with same BlastWave from minbias v 2 (p T,m) R y = 11.4 fm R x = 10.8 fm  0 = 8.3 fm/c  = 0 ( → ~1.5 fm/c w/ Bowler CC)) Consistent picture – convincing argument for flow scenario Saturation ???? s 2 = 0.045 Au+Au 130 GeV minbias asHBT versus BlastWave asHBT: geometry dominates dynamics Source out-of-plane extended

17. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO17 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-ph/0204061 (note: R O /R S puzzle persists)

18. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO18 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-ph/0204061

19. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO19 Further systematics in Au+Au 200 GeV Oscillation phases: out-of-plane extended source Source size increases, oscillations decrease with increasing centrality 0 th and 2 nd harmonics only Average size (0 th harmonic) falls with k T Mild evolution of 2 nd harmonic with k T Centrality cuts k T -integrated 12  bins k T cuts Mid-central 4  bins Centrality cuts k T -integrated 12  bins

20. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO20 “Grand summary” Fourier Coefficients Centrality- and k T - dependence of the  -dependence summarized concisely by Fourier coefficients central midcentral peripheral n = 0n = 2

21. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO21 “Grand summary” Fourier Coefficients Centrality- and k T - dependence of the  -dependence summarized concisely by Fourier coefficients central midcentral peripheral n = 0n = 2 Hydro predictions (*): b = 6 fm (*) Heinz & Kolb, hep-ph/0204061 “RHIC” source “LHC” (IPES) source Scale of homogeneity lengths off Phase/magnitude of oscillations from “RHIC” source in the ballpark significance ?

22. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO22 Evolution of spatial anisotropy Extraction of full freezeout scenario underway Timescales short, flow dominant Out-of-plane-extended freezeout geometry for all centralities –further constraint on evolution timescale (and dynamic models!!)

23. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO23 HBT systematics from 200 GeV similar to 130 GeV –New, more correct CC ~ 10-15% effect on R o Dynamic models (hydro, hydro+RQMD) –soft p-space signals  –soft x-space signals X –worse agreement with hadronic stage included BlastWave – toy model, but… –consistent framework to extract main features of freezeout –can initial state effects describe all signals as consistently? –in particular, short timescales  0,  -- perhaps the problem asHBT –probes details of anisotropic geometry/flow interplay –consistent w/ BW expectations (& further constrains f.o. picture) (ditto for non-identical particle correlations) –f.o. source out-of-plane extended (model-dependent in principle, but robust in fact) another constraint on evolution duration –detailed systematics from 200 GeV run hydro suggests this can reveal important physics tighter model constraints new level of presentation (FCs) for asHBT

24. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO24 Backups follow

25. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO25 Next slides Show Fabrice’s BW fits of published data Show BW vs Randy’s stuff –Rx=Ry and rho_a = 0 cases too Show Dan’s 3 centrality bins with 12 phi bins –2 nd order harmonics only Show Dan’s centrality/kT dependence Show “1-page summary,” with Heinz/Kolb on top Show Dan’s figure 4

26. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO26 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, PRC66 044903 (2002)

27. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO27 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, PRC66 044903 (2002)

28. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO28 Bowler CoulombCorrection vs  +  - Low k T High k T Work in progress: finalizing resolution effects, etc.

29. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO29 “Traditional HBT” - cylindrical sources 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)

30. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO30 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).

31. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO31 Recent analysis developments II Quick slide on pT vs kT cuts if Mercedes gets me a plot… Otherwise, forget it.. Not that important

32. STAR HBT 13 February 2003Winter Workshop - Breckenridge CO32 Need a model of the freezeout- BlastWave BW: hydro-inspired parameterization of freezeout longitudinal direction infinite extent geometrically boost-invariant longitudinal flow Momentum space temperature T transverse rapidity boost coordinate space transverse extents R X, R Y RYRY RXRX freezeout in proper time  evolution duration  0 emission duration  7 parameters describing freezeout