Bulk signatures & properties (soft particle production)

Does the thermal model always work ?  Particle ratios well described by T ch = 160  10 MeV,  B = 24  5 MeV  Resonance ratios change from pp to Au+Au  Hadronic Re-scatterings! Data – Fit (  ) Ratio

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

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

Resonance yields consistent with a hadronic re-scattering stage Generation/suppression according to x-sections p  **   K*    p K K p      More  Less K*  Chemical freeze-out K K  Ok   p  K K*/K  Less  * Preliminary

Lifetime and centrality dependence from  (1520) /  and K(892)/K 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= MeV  (1520)/  =   K*/K - = 0.20  0.03 at 0-10% most central Au+Au G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239 Life time: K(892) = 4 fm/c  (1520) = 13 fm/c preliminary More resonance measurements are needed to verify the model and lifetimes Blast wave fit of ,K,p (T kin +  T chem   ~ 6 fm/c Based on entropy:  t ~ (T ch /T kin – 1) R/  s  does not change much with centrality because slight  T reduction is compensated by slower expansion velocity  in peripheral collisions.

Time scales according to STAR data hadronization initial state pre-equilibrium QGP and hydrodynamic expansion hadronic phase and freeze-out dN/dt 1 fm/c 5 fm/c 10 fm/c20 fm/c time Chemical freeze out Kinetic freeze out Balance function (require flow) Resonance survival Rlong (and HBT wrt reaction plane) Rout, Rside

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

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

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

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 (v 2 ) Au+Au  s NN =200 GeV STAR Preliminary  68.3% CL  95.5% CL  99.7% CL

Collective Radial Expansion  r   increases continuously T th  saturates around AGS energy Strong collective radial expansion at RHIC  high pressure  high rescattering rate  Thermalization likely Slightly model dependent here: Blastwave model From fits to , K, p spectra:

Dynamics indicate common freezeout for most particles Chemical FO temperature About 70 MeV difference between T ch and T th : hadronic phase

Collective anisotropic flow x y z

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

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

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

v 2 measurements Multistrange v2 establishes partonic collectivity ?

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

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

A more direct handle? elliptic flow (v 2 ) and other measurements (not discussed)  evidence towards QGP at RHIC elliptic flow (v 2 ) 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? Are there more direct handles on the space-time geometry of collisions?  yes ! Even at the m / s scale ! What can they tell us about the QGP and system evolution? What can they tell us about the QGP and system evolution?

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

Probing source geometry through interferometry (Hanbury-Brown & Twiss (HBT) – photons from stars Measurable! F.T. of pion source Creation probability  (x,p) = U * U 5 fm 1 m  source  (x) r1r1 r2r2 x1x1 x2x2 p1p1 p2p2 The Bottom line… if a pion is emitted, it is more likely to emit another pion with very similar momentum if the source is small experimentally measuring this enhanced probability: quite challenging

Bose-Einstein correlations

HBT (GGLP) Basics In the simplest approximation, the technique has not changed since before most of you were born 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 For identical bosons/fermions But this (plane wave) approximation neglects many effects P(p 1,p 2 ;r 1,r 2 ) = P(p 1,p 2 )/P(p 1 )P(p 2 ) = 1 + |  (p 1 - p 2 ) | 2 ~ Gaussian source in x i yields Gaussian correlation in conjugate variable q i =p 1i- p 2i Who made first use of this pedagogic picture?

HBT Complexities We have neglected 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

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

q out q side q long Reminder R side R long R out x1x1 x2x2 p1p1 p2p2 Two-particle interferometry: p-space separation  space-time separation Two-particle interferometry: p-space separation  space-time separation R side R out Pratt-Bertsch (“out-side-long”) decomposition designed to help disentangle space & time source s p (x) = homogeneity region [Sinyukov(95)]  connections with “whole source” always model-dependent

beam direction More detailed geometry Relative momentum between pions is a vector  can extract 3D shape information p2p2 p1p1 q R long R side R out R long – along beam direction R out – along “line of sight” R side –  “line of sight”

STAR, PRL (2004) Measured final source shape central collisions mid-central collisions peripheral collisions Expected evolution:

More information Relative momentum between pions is a vector  can extract 3D shape information p2p2 p1p1 R out R long – along beam direction R out – along “line of sight” R side –  “line of sight” R side study as K grows…

Why do the radii fall with increasing momentum ??

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

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

Specific predictions of bulk global collective flow: space-momentum (x-p) correlations faster (high pT) particles come from smaller source closer to “the edge” Flow-generated substructure random (non-)system: all observers measure the “whole source”

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

Disintegration timescale Relative momentum between pions is a vector  can extract 3D shape information p2p2 p1p1 q R out R long – along beam direction R out – along “line of sight” R side –  “line of sight” R side  increases with emission timescale

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

Disintegration timescale - observation R O (fm) R S (fm) R O / R S increasing collision energy RHIC no threshold effect seen R O /R S ~ 1

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

Time scales according to STAR data dN/dt 1 fm/c 5 fm/c 10 fm/c20 fm/c time Chemical freeze out Kinetic freeze out Balance function (require flow) Resonance survival Rlong (and HBT wrt reaction plane) Rout, Rside hadronization initial state pre-equilibrium QGP and hydrodynamic expansion hadronic phase and freeze-out

 Initial energy density high enough to produce a QGP    10 GeV/fm 3 (model dependent)  High gluon density dN/dy ~ 800  1200 dN/dy ~ 800  1200  Proof for high density matter but not for QGP Summary: global observables

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

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