1 / 45

The HBT excitation function in relativistic heavy ion collisions

The HBT excitation function in relativistic heavy ion collisions. Mike Lisa Ohio State University. Plan. y. |b|. p T. I will discuss a set of zero measure in this rich parameter space what do we think we can learn from systematics in X (=y, p T , |b|…)?

sissy
Download Presentation

The HBT excitation function in relativistic heavy ion collisions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The HBT excitation functionin relativistic heavy ion collisions Mike Lisa Ohio State University

  2. Plan y |b| pT • I will discuss a set of zero measure in this rich parameter space • what do we think we can learn from systematics in X (=y, pT, |b|…)? • what do we think we have learned from systematics in X (=y, pT, |b|…)? • how does this change with s ? Also, upon request: comments on technical issues (event-mixing, Coulomb, non-Gaussianness, RP resolution correction…) Brief “summary” (intro to discussion)

  3. Reminder Rlong p1 qside x1 p2 qout Rside qlong x2 Rout • HBT: Quantum interference between identical particles 2 C (q) Gaussian model (3-d): 1 • Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for q (GeV/c) • Two-particle interferometry: p-space separation  space-time separation

  4. Reminder Rlong p1 qside x1 p2 qout Rside qlong x2 Rout Rside Rout • Two-particle interferometry: p-space separation  space-time separation Pratt-Bertsch (“out-side-long”) decomposition designed to help disentangle space & time

  5. E895 NPA661 444c (1999) E802 PRC66 054906 (2002) Au+Au 14.6 AGeV Si+Al 14.6 AGeV Si+Au 11.6 AGeV Au+Au • AGS: sNN  2-5 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear

  6. NA49 NPA661 448c (1999) RQMD 158 AGeV Pb+Pb 200 AGeV S+S 158 AGeV p+p • AGS: sNN  2-5 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear “initial” Rside • SPS: sNN  17-20 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear • apparent ~2x expansion

  7. AGS: sNN  2-5 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear • SPS: sNN  17-20 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear • apparent ~2x expansion NA44, Eur Phys J C18 317 (2000)

  8. STAR nucl-ex/0312009 accepted to PRL STAR PRL87 082301 (2001) PHENIX nucl-ex/0401003 32-72% 12-32% 0-12% • AGS: sNN  2-5 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear • SPS: sNN  17-20 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL: trend (and expectation) less clear • apparent ~2x expansion • RHIC: sNN = 130-200 GeV • Expected “geometric” scaling of transverse radii with |b|, Npart • RL trend very similar (expected?) • apparent ~2x expansion

  9. So far… • can learn: how does FO system size track with initial size? • did learn: transverse expansion ~2x • HBT radii appear to follow expected increases with (initial) system size(comforting to remember in present age of uncertainty) • Rlong(Npart) with s ? However, recall: HBT radii do not measure entire source,but “homogeneity regions” * * [Sinyukov, “Hot Hadronic Matter: Theory and Experiment,” NATO ASI Series B 346:309 (1995)]

  10. 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

  11. 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

  12. 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 MAL et al, PRC49 2788 (1994)

  13. 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)

  14. 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

  15. 80 AMeV Ar+Sc(pp,X) E895 PRL84 2798 (2000). y (fm) x (fm) • decreasing HBT R(p) present at all energies • sub-AGS energies (protons, IMFs) • cooling significant • AGS (and upward) – flow dominated • signs of trouble in s dep…(models work at one energy…) RQMD: Sorge PRC52 3291 (1995) MAL et al, PRL70 3709 (1993)

  16. E895 PRL84 2798 (2000) CERES, NPA714 124 (2003) STAR, PRL87 082301 (2001) • decreasing HBT R(p) present at all energies • sub-AGS energies (protons, IMFs) • cooling significant • AGS (and upward) – flow dominated • signs of trouble in s dep…(models work at one energy…) • SPS: smooth, almost (!) featureless transition AGS RHIC • can the models do that??! NB: error in CERES paper

  17. NA44) PRC58, 1656 (1998) D. Hardtke, Ph.D. thesis (1997) E895 PRL84 2798 (2000). • At fixed s, a chance to understand system • higher energy AGS: hadronic flow • @ lower s • could tune RQMD to give less flow… • model source too small and (maybe) emits too slowly? • SPS energy: • source too large? • model could be tuned… • already pre-RHIC: doubts of a complete understanding • but RQMD (nor hydro) did not get p-space perfectly, so… NA44RQMD Rout4.88  0.21 6.96  0.14 Rside4.45  0.32 6.23  0.20 Rlong6.03  0.35 7.94  0.21

  18. Kolb &Heinz, hep-ph/0204061 QM01 Heinz & Kolb, hep-ph/0204061 PHENIX, PRL91(’03)182301. Hydro: P.Huovinen et al.(’01) • RHIC: new hope! • hydro reproduces p-space very well with no/minimal tuning • details! • But alas! • hydro nor hydro+RQMDnor AMPT simultaneously gets p- and x-space • already pre-RHIC: doubts of a complete understanding • but RQMD (nor hydro) did not get p-space perfectly, so…

  19. Heinz & Kolb, hep-ph/0204061 dN/dt time • p-space observables well-understood within hydrodynamic framework • x-space observables not well-reproduced • correct dynamical signatures with incorrect dynamic evolution? • Too-large timescales modeled? • emission/freezeout duration (RO/RS) • evolution duration (RL)

  20. p-space observables well-understood within hydrodynamic framework • x-space observables not well-reproduced • correct dynamical signatures with incorrect dynamic evolution? • Too-large timescales modeled? • emission/freezeout duration (RO/RS) • evolution duration (RL) Retiere QM04 • Poor experimentalist’s exploratory tool: BW • tunable parameters (T, , timescales..) T=106 ± 1 MeV <bInPlane> = 0.571 ± 0.004 c <bOutOfPlane> = 0.540 ± 0.004 c RInPlane = 11.1 ± 0.2 fm ROutOfPlane = 12.1 ± 0.2 fm Life time (t) = 8.4 ± 0.2 fm/c Emission duration = 1.9 ± 0.2 fm/c c2/dof = 120 / 86 BW: F. Retiere & MAL, nucl-th/0312024

  21. Poor experimentalist’s exploratory tool: BW • tunable parameters (T, , timescales..) T=106 ± 1 MeV <bInPlane> = 0.571 ± 0.004 c <bOutOfPlane> = 0.540 ± 0.004 c RInPlane = 11.1 ± 0.2 fm ROutOfPlane = 12.1 ± 0.2 fm Life time (t) = 8.4 ± 0.2 fm/c Emission duration = 1.9 ± 0.2 fm/c c2/dof = 120 / 86 • Similar results from similar hydro-inspired models (e.g. Buda-Lund) Csanád, Csörgő, Lörstad nucl-th/0311102 and nucl-th/0310040

  22. 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! Csanád, Csörgő, Lörstad nucl-th/0311102 and nucl-th/0310040

  23. 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

  24. 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

  25. T T x (fm) 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

  26. 2 p+p+X Rlong Rout / Rout(pp) Rside / Rside(pp) Rout 1 Rside p+pstring fragmentation Au+AuCollective expansion Rlong / Rlong(pp) 0.25 0.5 pT • latest “puzzle” in HBT? • HBT radii from pp fall with pT(as observed previously, usually attributed to string kT kick)… • …but as much (proportionally) as dAu and AuAu ?? • coincidence…? • something deeper…? STAR, QM04 transverse plane

  27. local x-p corr. NB: p-space observables identical in the two cases • latest “puzzle” in HBT? • HBT radii from pp fall with pT(as observed previously, usually attributed to string kT kick)… • …but as much (proportionally) as dAu and AuAu ?? • coincidence…? • something deeper…? • What it does NOT mean: • AA=N*(strings) • AA=N*(“little blastwaves”) • AA: global x-p correlations

  28. So far… • HBT radii appear to follow expected increases with (initial) system size • comforting to remember in present age of uncertainty • Rlong(Npart)(s) less clear • can learn • what is nature of dynamic x-p correlations? • how strong is the flow? • what are the timescales involved? • did learn • emitting source dominated by (global) collective flow • HBT (and non-id) correlations described consistently with p-space • short evolution and emission timescales indicated • HBT “puzzle” puzzle? Get more information!

  29. Obtaining more detailed information in p-space… P. Kolb and U. Heinz, hep-ph/0204061 P. Kolb, nucl-th/0306081 “radial flow” “elliptic flow” • generically: breaking azimuthal symmetry (b0)  more differential detailed picture • HBT(): as v2, sensitive to interplay b/t anisotropic geometry & dynamics/evolution • another handle on dynamical timescales – likely impt in HBT puzzle

  30. ? in-plane-extended out-of-plane-extended What can we learn? Strongly-interacting 6Li released from an asymmetric trap O’Hara, et al, Science 298 2179 (2002) transverse FO shape + collective velocity  evolution time estimate check independent of RL(pT) Teaney, Lauret, & Shuryak nucl-th/0110037

  31. small RS big RS • observe the source from all angles with respect to RP • expect oscillations in HBT radii (including “new” cross-terms)

  32. y Au+Au 2 AGeV; E895, PLB 496 1 (2000) out side long 40 R2 (fm2) 20 x b os ol sl 10 0 -10 y 0 0 0 180 180 180 fp (°) x qs z (Beam) Coordinate space! • observe the source from all angles with respect to RP • expect oscillations in HBT radii (including “new” cross-terms) • At AGS: observed at2, 4, 6 AGeV Au+Au • including first-orderoscillations at y=0 • elliptical transverse shapes • strongly tilted w.r.t. beam • physics of directed flow

  33. Mike Lisa: 1 fm = 1/4” Images of p--emitting sources (scaled ~ x1014) qS=47° qS=33° qS=37° y z y z y z x ’ x ’ x ’ x x x similar to naïve overlap: b~5 fm 3 fm 2 AGeV 4 AGeV 6 AGeV Large, positive tilt angles E895 – QM01

  34. y x b y x qs z (Beam) Coordinate space! • observe the source from all angles with respect to RP • expect oscillations in HBT radii (including “new” cross-terms) • At AGS: observed at2, 4, 6 AGeV Au+Au • including first-orderoscillations at y=0 • elliptical transverse shapes • strongly tilted w.r.t. beam • physics of directed flow • At RHIC: • no 1st-order RP  no tilt (yet)

  35. observe the source from all angles with respect to RP • expect oscillations in HBT radii (including “new” cross-terms) • At AGS: observed at2, 4, 6 AGeV Au+Au • including first-orderoscillations at y=0 • elliptical transverse shapes • strongly tilted w.r.t. beam • physics of directed flow • At RHIC: • no 1st-order RP  no tilt (yet) • oscillations versus centrality • oscillations versus pT • average values  same as “traditional” HBT (sizes) • oscillations: transverse shape STAR, nucl-ex/0312009, PRL in press

  36. Estimate of initial vs F.O. source shape FO = init • estimate INIT from Glauber • from asHBT: • FO < INIT→ dynamic expansion • FO > 1 → source always OOP-extended • constraint on evolution time STAR, nucl-ex/0312009, PRL in press

  37. A simple estimate – 0 from init and final “radial flow” P. Kolb, nucl-th/0306081 • 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 valuable “evolutionary clock” constraint for models MAL ISMD03

  38. 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

  39.  (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: this year ? ?

  40. 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)

  41.  (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? • requires true 3D dynamical model (explicitly non-B.I.) STAR: this year ? ?

  42. Vf N CERES, PRL 90 (2003) 022301 • neglecting dynamics (flow), timescale, etc: is it trivial? • (though much of the interesting stuff is dynamics and timescales…) • gross geometrical features dictated by rule of critical mfp ~ 1 fm? Mean free path rough FO volume use measured:

  43. Same universal freeze-out in p+p, d+Au ? √s=200 GeV 90 90 d+Au Vf (fm3) 80 80 N (fm2) 70 70 60 60 50 50 40 40 30 30 p+p 20 20 10 10 0 • Check CERES’ ansatz using dN/dy’s and HBT radii for p+p and d+Au • dN/dy’s taken from power-law fits to STAR pT spectra (nucl-ex/0309012) Vf N CERES, PRL 90 (2003) 022301 • f ~ 1 fm seems to hold for light systems as well (!) • Why are p+p, d+Au and Au+Au so similar? Magestro, QM04 Dan Magestro, Ohio State University

  44. broad strokes… (shorter than usual) • first order: “R=6 fm” (though this means 2x expansion) • Well… R=(1.2 fm)*A1/3 • Well… R ~ (Npart)1/3 • HBT radii are, indeed, connected with geometry… • but these are easy rules: dynamical models cannot follow them? • pT, m1-m2 dep: • strong global collective flow dominates • -dep: freezeout in out-of-plane configuration • non-trivial aspect of excitation function • IMHO: Soft-sector dynamical observations (x- and p-space) demand faster timescales than present understanding allows. • e.g. maybe essentially no hadronic phase? • personal most worrisome “puzzle”: pp = “small AA”??

  45. parting words • s scan of HBT worthless? (not huge changes) • no! at one energy, we would (mistakenly) believe we understood space-time structure of collisions • Experimental HBT dataset is richly structured, with huge systematics and expertise available • IMHO, real work needed on theory side, and not dismissal • (meanwhile, experimentalists will mess around with BW to try to discern what the data is telling us) • Puzzles may be annoying speedbumps on the way (to Stockholm?), but one ignores them at one’s peril.

More Related