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Bulk signatures & properties (soft particle production)

Bulk signatures & properties (soft particle production). Does the thermal model always work ?. Data – Fit ( s ) Ratio. Particle ratios well described by T ch = 160  10 MeV, m B = 24 5 MeV Resonance ratios change from pp to Au+Au  Hadronic Re-scatterings!.

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Bulk signatures & properties (soft particle production)

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  1. Bulk signatures & properties (soft particle production)

  2. Does the thermal model always work ? Data – Fit (s) Ratio • Particle ratios well described by Tch = 16010 MeV, mB = 24 5 MeV • Resonance ratios change from pp to Au+Au  Hadronic Re-scatterings!

  3. Strange resonances in medium Short life time [fm/c] K* < *< (1520) <  4 < 6 < 13 < 40 Rescattering vs. Regeneration ? Medium effects on resonance and their decay products before (inelastic) and after chemical freeze out (elastic). Red: before chemical freeze out Blue: after chemical freeze out

  4. ResonanceProduction in p+p and Au+Au Life time [fm/c] :  (1020) = 40 L(1520) = 13 K(892) = 4 ++ = 1.7 Thermal model [1]: T = 177 MeV mB = 29 MeV UrQMD [2] [1] P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication [2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher, private communication Rescattering and regeneration is needed !

  5. Resonance yields consistent with a hadronic re-scattering stage • Generation/suppression according to x-sections p p D p Preliminary r/p p p D L* D/p More D K Chemical freeze-out f/K f Ok p p r p p Less K* K*/K p r K* Less L* L*/L K K f 0.1 0.2 0.3 K

  6. Blast wave fit of p,K,p (Tkin +b) + Tchem • Dt ~ 6 fm/c Based on entropy: Dt ~ (Tch/Tkin – 1) R/bs • Dt does not change much with centrality • because slight DT reduction is compensated by slower expansion velocity b in peripheral collisions. preliminary More resonance measurements are needed to verify the model and lifetimes Lifetime and centrality dependence from (1520) / and K(892)/K G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239 Life time: K(892) = 4 fm/c L(1520) = 13 fm/c • Model includes: • Temperature at chemical freeze-out • Lifetime between chemical and thermal freeze-out • By comparing two particle ratios (no regeneration) • results between : • T= 160 MeV =>  > 4 fm/c(lower limit !!!) •  = 0 fm/c => T= 110-130 MeV (1520)/ = 0.034  0.011  0.013 K*/K- = 0.20  0.03 at 0-10% most central Au+Au

  7. hadronic phase and freeze-out QGP and hydrodynamic expansion initial state Balance function (require flow) pre-equilibrium Resonance survival hadronization Rout, Rside Rlong (and HBT wrt reaction plane) dN/dt time 5 fm/c 1 fm/c 10 fm/c 20 fm/c Chemical freeze out Kinetic freeze out Time scales according to STAR data

  8. BRAHMS: 10% central PHOBOS: 10% PHENIX: 5% STAR: 5% Identified Particle Spectra for Au-Au @ 200 GeV • The spectral shape gives us: • Kinetic freeze-out temperatures • Transverse flow • The stronger the flow the less appropriate are simple exponential fits: • Hydrodynamic models (e.g. Heinz et al., Shuryak et al.) • Hydro-like parameters (Blastwave) • Blastwave parameterization e.g.: • Ref. : E.Schnedermann et al, PRC48 (1993) 2462 Explains: spectra, flow & HBT

  9. Blastwave: a hydrodynamic inspired description of spectra Spectrum of longitudinal and transverse boosted thermal source: bs R Ref. : Schnedermann, Sollfrank & Heinz, PRC48 (1993) 2462 Static Freeze-out picture, No dynamical evolution to freezeout

  10. STAR preliminary Heavy (strange ?) particles show deviations in basic thermal parametrizations

  11. Blastwave fits • Source is assumed to be: • In local thermal equilibrium • Strongly boosted • , K, p: Common thermal freeze-out at T~90 MeV and <>~0.60 c • : Shows different thermal freeze-out behavior: • Higher temperature • Lower transverse flow • Probe earlier stage of the collision, one at which transverse flow has already developed • If created at an early partonic stage it must show significant elliptic flow (v2) Au+Au sNN=200 GeV STAR Preliminary  68.3% CL 95.5% CL 99.7% CL

  12. Collective Radial Expansion From fits to p, K, p spectra: • <r > • increases continuously • Tth • saturates around AGS energy • Strong collective radial expansion at RHIC • high pressure • high rescattering rate • Thermalization likely Slightly model dependent here: Blastwave model

  13. Dynamics indicate common freezeout for most particles Chemical FO temperature About 70 MeV difference between Tch and Tth: hadronic phase

  14. z y x Collective anisotropic flow

  15. Elliptic Flow(in the transverse plane)for a mid-peripheral collision Flow Y Out-of-plane In-plane Reaction plane Flow X Dashed lines: hard sphere radii of nuclei Re-interactions  FLOW Re-interactions among what? Hadrons, partons or both? In other words, what equation of state?

  16. Anisotropic Flow y f x z x Transverse plane Reaction plane A.Poskanzer & S.Voloshin (’98) “Flow” is not a good terminology especially in high pT regions due to jet quenching. 0th: azimuthally averaged dist.  radial flow 1st harmonics: directed flow 2nd harmonics: elliptic flow …

  17. Hydrodynamics describes the data Strong collective flow: elliptic and radial expansion with mass ordering Hydrodynamics: strong coupling, small mean free path, lots of interactions NOT plasma-like

  18. v2 measurements Multistrange v2 establishes partonic collectivity ?

  19. # III: The medium consists of constituent quarks ? baryons mesons

  20. Ideal liquid dynamics –reached at RHIC for the 1st time

  21. A more direct handle? • elliptic flow (v2) and other measurements (not discussed)  evidence towards QGP at RHIC • indirect connection to geometry • Are there more direct handles on the space-time geometry of collisions? • yes ! Even at the 10-15 m / 10-23 s scale ! • What can they tell us about the QGP and system evolution?

  22. Volumes & Lifetimes= 2nd Law Thermodynamics • Ideal Gas • Relativistic Fermi/Bose Gasm=0 • Pions (3) vs. QGP (37)

  23. The Bottom line… if a pion is emitted, it is more likely to emit another pionwith very similar momentumif the source is small Creation probability r(x,p) = U*U F.T. of pion source Measurable! Probingsource geometry through interferometry(Hanbury-Brown & Twiss (HBT) – photons from stars p1 r1 x1 p source r(x) 1 m x2 r2 p2 experimentally measuring this enhanced probability: quite challenging 5 fm

  24. Bose-Einstein correlations

  25. ~ P(p1,p2)/P(p1)P(p2) = 1 + | r(p1 - p2) |2 HBT (GGLP) Basics • In the simplest approximation, the technique has not changed since before most of you were born Goldhaber, Goldhaber, Lee, and Pais, PR 120:300 (1960) • For identical bosons/fermions P(p1,p2;r1,r2) = Who made first use of this pedagogic picture? Gaussian source in xi yields Gaussian correlation in conjugate variable qi=p1i-p2i But this (plane wave) approximation neglects many effects

  26. HBT Complexities • We have neglected • Final state interactions • Coulomb interaction • Strong interaction • Weak decays • Position-momentum correlations • Things more subtle, such as special relativity State of the art analysis incorporates most of these, but not all

  27. Au+Au R ~ 6 fm p+p R ~ 1 fm d+Au R ~ 2 fm Correlation functions for different colliding systems STAR preliminary C2(Qinv) Qinv (GeV/c) Different colliding systems studied at RHIC Interferometry probes the smallest scales ever measured !

  28. 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

  29. p1 Rlong q Rside p2 Rout beam direction More detailed geometry Relative momentum between pions is a vector  can extract 3D shape information Rlong – along beam direction Rout – along “line of sight” Rside–  “line of sight”

  30. central collisions mid-central collisions peripheral collisions Measured finalsource shape STAR, PRL93 012301 (2004) Expected evolution: ?

  31. p1 p2 More information Relative momentum between pions is a vector  can extract 3D shape information Rlong – along beam direction Rout – along “line of sight” Rside –  “line of sight” Rout Rside study as K grows…

  32. Why do the radii fallwith increasing momentum ??

  33. Geometric substructure? random (non-)system: all observers measure the “whole source”

  34. Why do the radii fallwith increasing momentum ?? It’s collective flow !! Direct geometrical/dynamical evidence for bulk behaviour!!!

  35. 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”

  36. Timescales • Evolution of source shape • suggests system lifetime is shorter than otherwise-successful theory predicts • Is there a more direct handle on timescales?

  37. p1 q p2 Disintegration timescale Relative momentum between pions is a vector  can extract 3D shape information Rlong – along beam direction Rout – along “line of sight”  increases with emission timescale Rside –  “line of sight” Rout Rside

  38. Disintegration timescale - expectation Rischke & Gyulassy, NPA 608, 479 (1996) 3D 1-fluid Hydrodynamics with transition with transition “” “” • Long-standing favorite signature of QGP: • increase in , ROUT/RSIDE due to deconfinement  confinement transition • expected to “turn on” as QGP energy threshold is reached

  39. 8 8 6 6 RO (fm) 4 4 RS (fm) 1.5 1.25 RO / RS 1.0 increasing collision energy Disintegration timescale - observation • no threshold effect seen • RO/RS ~ 1 RHIC

  40. Heinz & Kolb, hep-ph/0204061 An important space-time “puzzle” at RHIC - actively under study Disintegration timescale - observation • no threshold effect seen • RO/RS ~ 1 • toy model calculations suggest very short timescales • rapid, explosive evolution • too explosive for “real” modelswhich explain all other data N()

  41. hadronic phase and freeze-out QGP and hydrodynamic expansion initial state pre-equilibrium hadronization Time scales according to STAR data Balance function (require flow) Resonance survival Rout, Rside Rlong (and HBT wrt reaction plane) dN/dt time 5 fm/c 1 fm/c 10 fm/c 20 fm/c Chemical freeze out Kinetic freeze out

  42. Summary: global observables • Initial energy density high enough to produce a QGP • e 10 GeV/fm3 (model dependent) • High gluon density dN/dy ~ 800-1200 • Proof for high density matter but not for QGP

  43. Summary of particle identified observables Statistical thermal models appear to work well at SPS and RHIC • Chemical freeze-out is close to TC • Hadrons appear to be born into equilibrium at RHIC (SPS) • Shows that what we observe is consistent with thermalization • Thermal freeze-out is common for all particles if radial flow is taken into account. T and bT are correlated • Fact that you derive T,bT is no direct proof but it is consistent with thermalization

  44. Conclusion • There is no “ “ in bulk matter properties • However: • So far all pieces point indeed to QGP formation - collective flow & radial - thermal behavior - high energy density elliptic

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