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Femtoscopy in heavy ion collisions: Wherefore, Whence, & Whither?

Femtoscopy in heavy ion collisions: Wherefore, Whence, & Whither?. Wherefore (=“why?”) motivation & (basic) formalism. Mike Lisa Ohio State University. Whence (=“from where?”) systematics over 2 decades. Whither (=“to where?”) or “wither”...?. MAL, Pratt, Soltz, Wiedemann

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Femtoscopy in heavy ion collisions: Wherefore, Whence, & Whither?

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  1. Femtoscopy in heavy ion collisions:Wherefore, Whence, & Whither? • Wherefore (=“why?”) • motivation & (basic) formalism Mike Lisa Ohio State University • Whence (=“from where?”) • systematics over 2 decades • Whither (=“to where?”) • or “wither”...? MAL, Pratt, Soltz, Wiedemann Ann Rev Nucl Part Sci 55 (2005) http://www-rnc.lbl.gov/TBS mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  2. Ann.Rev.Nucl.Part.Sci. 46 (1996) 71 STAR, PRC66 (2002) 034904 STAR, PRL93 (2004) 252301 Spacetime - The characteristic of H.I.C. • Non-trivial space-time - the hallmark of R.H.I.C. • Initial state: dominates further dynamics • Intermediate state: impt element in exciting signals • Final state: • Geometric structural scale is THE defining feature of QGP • Temporal scale sensitive to deconfinement transition (?) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  3. Gaussian parameterization of a-b separation pa pa pb pb xa xa xa for identical pions xb xb xb • F(Qinv) = integrated squared Coulomb wavefunction • “contamination” included via  • NB: Gaussian source: not Gaussian CF Extraction of length scales maximum-likelihood fit to usually used (even for non-id) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  4. Rlong p1 qside x1 p2 qout Rside qlong x2 Rout Rside Rout Reminder • Two-particle interferometry: p-space separation  space-time separation source sp(x) = homogeneity region [Sinyukov(95)]  connections with “whole source” always model-dependent Pratt-Bertsch (“out-side-long”) decomposition designed to help disentangle space & time mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  5. Disintegration timescale - INITIAL expectation 3D 1-fluid Hydrodynamics Rischke & Gyulassy, NPA 608, 479 (1996) with transition “” “” • Long-standing favorite signature of QGP: • increase in , ROUT/RSIDE due to deconfinement  confinement transition • hoped-for “turn on” as QGP threshold is reached mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  6. A.D. Chacon et al, Phys. Rev. C43 2670 (1991) G. Alexander, Rep. Prog. Phys. 66 481 (2003) AGS/SPS/RHIC HBT papers (expt) Heinz/Jacak Wiedemann/Heinz Csorgo 20 R = 1.2 (fm)•A1/3 Tomasik/Wiedemann Boal/Jennings/Gelbke 15 10 5 ‘85 ‘90 ‘95 ‘00 ‘05 Two decades of systematics Lisa, Pratt, Soltz, Wiedemann “R = 5 fm” • Pion HBT @ Bevalac: “largely confirming nuclear dimensions” • Since 90’s: increasingly detailed understanding and study w/ high stats mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  7. AGS/SPS/RHIC HBT papers (expt) Heinz/Jacak Wiedemann/Heinz Csorgo 20 Tomasik/Wiedemann Boal/Jennings/Gelbke 15 y 10 5 |b| ‘85 ‘90 ‘95 ‘00 ‘05 pT Two decades of systematics Lisa, Pratt, Soltz, Wiedemann • Pion HBT @ Bevalac: “largely confirming nuclear dimensions” • Since 90’s: increasingly detailed understanding and study w/ high stats mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  8. Repeating most basic sanity check at relativistic energies... Forget homogeneity regions or fancy stuff. Do femtoscopic length scales increase when they “should?” p-p correlations * big bump  small source • Also • SPS [NA44(‘99),NA49(‘00)] • RHIC [STAR(‘05)] mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  9. Au+Au sNN =200 GeV Varying initial “source size” Fixed b : vary A (& B!) Fixed A+B : vary b b Likely scaling variable: Npart PHENIX, PRL 2004 • Generalize A1/3Npart1/3 • not bad @ RHIC! • connection w/ init. size? mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  10. PHOBOS • Generalize A1/3Npart1/3 • not bad @ RHIC! • connection w/ init. size? • Heavy and light data from AGS, SPS, RHIC • ~s-ordering in “geometrical” Rlong, Rside • Mult ~ K(s)*Npart • source of residual s dep? • ...Yes! common scaling • final state drives radii, not init. geometry • (breaks down s < 5 GeV) NB: not constant density LPSW nucl-ex/0505014 mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  11. H. Caines (STAR) QM05 H. Caines (STAR) QM05 NA57 (open) STAR (filled) NA57 (open) STAR (filled) S. Manly (PHOBOS) QM05 Tounsi, Mischke, Redlich NPA715 565 (2003) We are not alone... Entropy determines “everything” at bulk level (soft sector) ? c.f. Helen’s talk NB: scaling violated s < 4 GeV (as with femtoscopy) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  12. Vf N ~ FO volume x-section: CERES, PRL 90 (2003) 022301 m.f.p Refinement: chemical effects • different behaviour below/above AGS • violates “universal” scaling • baryon  meson dominance • neglect time/dynamics: gross F.O. geometry appears determined by • chemistry • “universal” mean free path ~ 1 fm(!?) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  13. c.f. Chajecki - lighter systems Messages from systematics • AB, |b|, Npart systematics • sanity check on overall size dependence  • final state multiplicity/chemistry determines rough geometry... ...and that geometry is ~2x initial size collective/flow-like expansion?  probe anisotropically! mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  14. ? in-plane-extended out-of-plane-extended Strongly-interacting 6Li released from an asymmetric trap O’Hara, et al, Science 298 2179 (2002) What can we learn? transverse FO shape + collective velocity  evolution time estimate check independent of RL(pT) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy Teaney, Lauret, & Shuryak nucl-th/0110037

  15. small RS big RS • observe the source from all angles with respect to RP • expect oscillations in HBT radii mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  16. side side out out • observe the source from all angles with respect to RP • expect oscillations in HBT radii (including “new” cross-terms) R2out-side<0 when pair=135º mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  17. STAR, PRL93 012301 (2004) Measured final source* shape R2out-side<0 when pair=135º ever see that symmetry at ycm ? * model-dependent, but see Retiere & MAL PRC70 044907 2004 mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  18. STAR, PRL93 012301 (2004) central collisions mid-central collisions peripheral collisions Measured final source* shape Expected evolution: ? * model-dependent, but see Retiere & MAL PRC70 044907 2004 mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  19. STAR PRL93 012301 (2004) initial= final c.f. Chajecki - lighter systems Evolution of size and shape - “the rule of two” ~ 1/2 shape reduction ~ x2 size increase Initial size/shape estimated by Glauber calculation Final config according to Retiere & MAL PRC70 044907 2004 mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  20. AGS: FO  init RHIC: FO < init (approximately same centrality) sNN (GeV) is relation b/t final and  near quantitatively sensible? “Anisotropic sanity check” • non-trivial excitation function • does it make sense? Is it related to bulk dynamics? • YES (in a toy model yes - fordiscusison if asked) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  21. Messages from systematics • AB, |b|, Npart systematics • sanity check on overall size dependence  • final state multiplicity/chemistry determines rough geometry... • , |b|, s systematics • sanity check on shape evolution  • geometric evolution ~ consistent with collective bulk dynamics (flow) look for dynamic signatures & substructure • more than T versus mass • more than spectral shapes • more than v2 • ... • flow is defined by space-momentum correlations • only femtoscopy can probe substructure • of dynamic bulk behaviour mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  22. Geometric substructure? random (non-)system: all observers measure the “whole source” mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  23. Flow-generated substructure random (non-)system: all observers measure the “whole source” • Specific predictions ofbulk global collective flow: • space-momentum (x-p) correlations • faster (high pT) particles come from • smaller source • closer to “the edge” mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  24. what agreement!! (what agreement?) LPSW(05) Strong flow confirmed by all expts... mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  25. Spectra v2 HBT Flow-dominated “Blast-wave” model PRC70 044907 (2004) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  26. Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations early times: small, hot source late times: large, cool source mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  27. MAL et al, PRC49 2788 (1994) • Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  28. Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations • hot core surrounded by cool shell • important ingredient of Buda-Lund hydro picturee.g. Csörgő & LörstadPRC54 1390 (1996) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  29. Each scenario generates x-p correlations • Decreasing R(pT) • usually attributed to collective flow • flow integral to our understanding of R.H.I.C.; taken for granted • femtoscopy the only way to confirm x-p correlations – impt check but… x2-p correlation: yes x-p correlation: yes • Non-flow possibilities • cooling, thermally (not collectively) expanding source • combo of x-t and t-p correlations • hot core surrounded by cool shell • important ingredient of Buda-Lund hydro picturee.g. Csörgő & LörstadPRC54 1390 (1996) x2-p correlation: yes x-p correlation: no t x2-p correlation: yes x-p correlation: no mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  30. Spectra v2 R (fm) space-momentum substructure mapped in detail STAR PRL 91 262301 (2003) HBT mT (GeV/c) Flow-dominated “Blast-wave” model PRC70 044907 (2004)  K mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  31. RHIC femtoscopy with wide variety of particle species R(√SNN, b, Npart, A, B, mT, y, ,PID1, PID2)  = prelim or final result available mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  32. Finally, we understand it! M Gyulassy ‘95 Just one event! RHIC serves the perfect liquid Trends, soft sector, and RHI history A. Wetzler (2005) • unlike hard and “intermediate” sectors, soft sector has “decades” of systematics Then: p-dependent potentials, surface effects, hard-cores, absoption... mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  33. model comparisons • unlike hard and “intermediate” sectors, soft sector has “decades” of systematics • single-point agreement a bit unsatisfying... • femtoscopic model comparisons: mostly “HBT radii” in b=0 collisions • RHIC models only expected to work at highest energies... mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  34. LPSW(05) Comparison to “perfect” hydro calculations • model sensitivity (not just R=5) • Rout too big (too long emission time?) • Rlong too big (too long evolution time?) • Rside too small (?) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  35. Comparison to Boltzmann/cascade models better! (better than “perfect”...?) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  36. fit calculated* 3D C(q) to Gaussian functional form: “HBT radii” from variances *later: how it is calculated What’s the difference? freeeze-out........ EoS............viscosity hydro cascade should be the same IF source is Gaussian mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  37. Hydrodynamics - CE EOS Frodermann, Heinz, MAL PRC63 (2006) Blast Wave Frodermann, Heinz, MAL PRC63 (2006) Hydrodynamics - NCE EOS Frodermann, Heinz, MAL PRC63 (2006) C2 C2 C2    qs (GeV/c) qs (GeV/c) qs (GeV/c) • Depending on model (& parameters, like EoS), • non-Gauss effects may be important, (also, Hirano, Ko/Li, Rischke) • BW - no big effect • “perfect” hydro - pushes results into “right” direction. NCE EoS close RO RS RL  KT (GeV/c) KT (GeV/c) KT (GeV/c) KT (GeV/c) KT (GeV/c) KT (GeV/c) Non-Gaussian Effects and Model Comparisons - Hydro/BW mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  38. Wherefore & Whence R(√SNN, b, Npart, A, B, mT, y, ,PID1, PID2) • size & shape; timescale estimate • space-momentum substructure of a flowing system;dynamics and evolution of • radial flow (size and shift) • elliptic flow (shape and timescale) • directed flow (shape and tilt) [did not show due to time] • hadronic particle potentials / phase shifts • Femtoscopy: • well-calibrated, well-established tool • the one most directly connected to space-time - THE defining feature of R.H.I.C. • huge set of systematics of consistent measurements • sensitive to physics in models • with care: the femtoscope is a precision tool to apply to new systemsLHC, p+p, etc mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  39. Whither? • non-id correlations for b≠0[Retiere & Lisa PRCPRC70 044907 (2004)] • invert the problem : low-energy phaseshifts from exotic pairs (e.g. -) [talk of H. Gos] &[P. Chaloupta QM05] • space-time substructure in p+p ?? - “direct comparison] [talk of Z. Chajecki][Chajecki et al, WW05] • imaging - beyond sizes and shifts [Brown, Danielewicz, Pratt, & others] • first-order azimuthally-sensitive femtoscopy - spacetime aspects of v1[Lisa et al, PLB489 287; PLB496 1] • relative jets, spin.... (?) • continue/expand rich program @ ALICE/LHC mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  40. THEEND mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  41. Strong flow confirmed by all expts... Central (~10%) AuAu (PbPb) collisions at y~0 mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  42. “radial flow” P. Kolb, nucl-th/0306081 A simple estimate – 0 from init and final • BW → X, Y @ F.O. (X > Y) • hydro: flow velocity grows ~ t • From RL(mT): 0 ~ 9 fm/c • consistent picture • Longer or shorter evolution times • inconsistent • toy estimate: 0 ~ 0(BW)~ 9 fm/c • too short to account for expansion?? • Need a real model comparison→ asHBT workable “evolutionary clock” constraint for models MAL ISMD03 mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  43. Motivation Formalism Experiment Trends Models 1D projections: a limited view STAR PRC71 044906 (2005) • Usually, quality of data and fit shown in 1D projections • Narrow integration best • limited view of data • see talks of Adam, Scott, Sandra • tomorrow: a better way out “Gaussian fit” (remember: not Gaussian CF) side long mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  44. Motivation Formalism Experiment Trends Models The perennial non-Gaussianness • Source has never been fully Gaussian. c.f. J. Sullivan @ SPS • periodically re-discovered, with little change; information condensation needed to observe systematic data trends • non-Gaussianness @ RHIC reported in first and subsequent HBT measurements • imaging is probably best solution (but even then...) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  45. Motivation Formalism Experiment Trends Models RS (fm) RO (fm) RO/RS Rl (fm) The perennial non-Gaussianness • CF is “mostly” Gaussian • STAR tried “Edgeworth” functional expansion (Csorgo 2000) among few quantitative estimates of non-Gaussian shape STAR PRC71 044906 (2005) • 20% effect in Rlong! systematic error...? • appears fit captures dominant length scale mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  46. Another implication of strong flow: ~ mT scaling mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  47. using four of the six “radii” AGS: FO  init RHIC: FO < init (approximately same centrality) sNN (GeV) • transverse shape: • non-trivial excitation function • increased flow*time  rounder FO geometry @ RHIC • insufficient [flow]x[time] to become in-plane mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  48. using ALL of the six “radii” Au+Au sNN = 2.3 GeV; b5 fm E895, PLB496 1 (2000) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  49.  (o) y x qs sNN (GeV) z (Beam) AGS • transverse shape: • non-trivial excitation function • increased flow*time  rounder FO geometry @ RHIC • insufficient [flow]x[time] to become in-plane • Spatial orientation: • another handle on flow & time • HUGE tilts @ AGS!! • RHIC? • QGP-induced orientation? STAR: soon ? ? mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

  50. v1 predictions (QGP invoked) x-p transverse-longitudinal coupling may be affected in early (v1) stage L.P. Csernai, D. Rohrich: Phys. Lett. B 458 (1999) 454 J. Brachmann et al., Phys. Rev. C. 61 024909 (2000) mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

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