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Femtoscopy in heavy ion collisions: Two decades of progress

Femtoscopy in heavy ion collisions: Two decades of progress. Mike Lisa Ohio State University. An experimentalist’s view of the situation B.Q.M.( * ) cf. Bysterský, Chajecki, Chaloupka, Chung, Kisiel, Kniege, Panitkin. * BQM= Before Quark Matter. Outline. Relevance of femtoscopy to R.H.I.C.

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Femtoscopy in heavy ion collisions: Two decades of progress

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  1. Femtoscopy in heavy ion collisions:Two decades of progress Mike Lisa Ohio State University An experimentalist’s view of the situation B.Q.M.(*) cf. Bysterský, Chajecki, Chaloupka, Chung, Kisiel, Kniege, Panitkin... * BQM= Before Quark Matter mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  2. Outline • Relevance of femtoscopy to R.H.I.C. • Growing activitiies of a (sub)field : 2 decades of systematics • R(√SNN, b, Npart, A, B, mT, y, ,PID) • what information is encoded? • what have we mined so far? • special attention to size and shape • comments blastwave comparison to models experimental details mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  3. STAR, PRC66 (2002) 034904 STAR, PRL93 (2004) 252301 Spacetime - an annoying bump on the road to Stockholm? • Non-trivial space-time - the hallmark of rhic • Initial state: dominates further dynamics • Intermediate state: impt element in exciting signals • Final state: • Geometric structural scale is THE defining feature of QGP mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  4. Ann.Rev.Nucl.Part.Sci. 46 (1996) 71 Spacetime - an annoying bump on the road to Stockholm? • Non-trivial space-time - the hallmark of rhic • 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  5. 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 “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 - WPCF Aug 2005 - Kroměříž Czech Republic

  6. 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 • 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  7. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  8. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  9. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  10. 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) ? NB: scaling violated s < 4 GeV (as with femtoscopy) mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  11. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  12. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  13. ? 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 - WPCF Aug 2005 - Kroměříž Czech Republic Teaney, Lauret, & Shuryak nucl-th/0110037

  14. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  15. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  16. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  17. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  18. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  19. 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 mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  20. “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 - WPCF Aug 2005 - Kroměříž Czech Republic

  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 - WPCF Aug 2005 - Kroměříž Czech Republic

  22. Spectra v2 HBT Flow-dominated “Blast-wave” model PRC70 044907 (2004) mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  23. 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 Kolb & Heinz, QGP3 nucl-th/0305084 mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  24. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  25. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  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 • 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  27. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  28. pT T • flow-dominated “models” can reproduce soft-sector x-space observables • imply short timescales • however, are we on the right track? [flow] • puzzles?  check your assumptions! • look for flow’s “special signature”x-p correlation • In flow pictures, low-pT particles emitted closer to source’s center (along “out”) • non-identical particle correlations(FSI at low v) probe: • (x1-x2)2 (as does HBT) • x1-x2  K p [click for more details on non-id correlations] F. Retiere & MAL, nucl-th/0312024 Csanád, Csörgő, Lörstad nucl-th/0311102 and nucl-th/0310040 mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  29. T T x (fm) QM02 x (fm) A. Kisiel (STAR) QM04 • extracted shift in emission point x1-x2 consistent w/ flow-dominated blastwave • In flow pictures, low-pT particles emitted closer to source’s center (along “out”) • non-identical particle correlations(FSI at low v) probe: • (x1-x2)2 (as does HBT) • x1-x2 mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  30. 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 - WPCF Aug 2005 - Kroměříž Czech Republic

  31. LPSW(05) - DATA in color-- experimentalist’s plot what agreement!! (what agreement?) Strong flow confirmed by all expts... mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  32. Strong flow confirmed by all expts... Central (~10%) AuAu (PbPb) collisions at y~0 mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  33. Another implication of strong flow: ~mT scaling mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  34. inconsistent with boost-invariance Motivation Formalism Experiment Trends Models PHOBOS nucl-ex/0410022 Some longitudinal systematics consistent with boost-invariance mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  35. beam “Dynamic” BI without “Chemical” BI ? Only femtoscopy can tell! mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  36. beam “Dynamic” BI without “Chemical” BI ? Only femtoscopy can tell! mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  37. sizes and offsets in impact parameter and longitudinal directions E877, Miskowiec CRIS’98 nucl-ex/9808003 C p-- 10 fm b qX (GeV/c) qY (GeV/c) qZ (GeV/c) z Greater detail - -p correlations @ AGS mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

  38. We are working on the many slowly crawling ants... ... don’t give up your dreams!! Comments • massive systematic program provides tremendous geometric detail • each element reasonable by itself not really “puzzling.” • “critical mass” in the femtoscopy community • Related, but not in my talk: important new directions [talks @ WPCF] • moments analysis • imaging • continued emphasis on non-identical particle correlations • connection to “elementary” systems - communication “across lines” • Important puzzles beyond central Au+Au at top energy • Ignoring femtoscopy to pursue “perfection” is unjustified • Space-time is the defining feature of R.H.I.C. • Femtoscopy does measure space-time • The measurements are sensitive to underlying physics mike lisa - Femtoscopy in relativistic heavy ion collisions - WPCF Aug 2005 - Kroměříž Czech Republic

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