Particle correlations in such collision?! N=n(n-1)/2. azimuthal, back-to back, multiplicity... close velocity,

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1 Future of Nuclear Collisions at High Energies Kielce, Poland, October Particle correlations in heavy ion collisions Jan Pluta Warsaw University of Technology Faculty of Physics, Heavy Ion Reactions Group (HIRG),

2 Particle correlations in such collision?! N=n(n-1)/2 q azimuthal, back-to back, multiplicity... close velocity,

3 Particle correlations as a tool to explore the space-time geometry and dynamics The idea: HBT+FSI Quantum statistics and Final-State Interaction Space-time sizes and dynamics (cannot be measured directly) close velocity correlations Momenta and momentum difference (can be measured)

4 Role of momentum correlations in interpreting QGP signatures Probe the emitting source structure at decupling Identify traces left behind by the QGP Test the relations between collective expansion and thermal motion Measure the spatial deformations of the source Distinguish between different models of collision dynamics

5 Dependencies to be verified beam energy transverse momentum (k T ) particle species collision system azimuthal angle onset effects, transition phenomena dynamics, collective expansion differences in emission origins of correlations, phase space spatial anisotropies, constrain system evolution

6 Who can do it? How to do it 2 nd Warsaw Meeting on Particle Correlations and Resonances in Heavy Ion Collisions Warsaw University of Technology October 2003

7 Some words about formalism R side R long x 2 x 1 p 1 q side p 2 q r q out r q r k = = r r p 2 p r r p 2 p 1 ( + ) q long R out Gaussian model (3-d): P( p1, p2) C( p1, p2) = = P( p1)p( p2) r r v 2 qout C( q, k ) = 1+ λ( k ) e R real event pairs mixed event pairs 2 out q 2 side R 2 side q 2 long R 2 long C (q) 2 1 ~ 1 R Final-state effects (Coulomb, strong) also can cause correlations, need to be included q (GeV( GeV/c)

8 Mercedes Lopez-Noriega, QM 2002 HBT Excitation Function Comparison with lower energies for ~ 10% most central events at midrapidity k T ~ 0.17 GeV/c No significant increase in radii with energy R O /R S ~ 1

9 Consistency test of RHIC experiments A highlight from this week Burt Holzman, PHOBOS

10 RHIC HBT puzzle unexpected (small) sizes R out /R side = (approx.)1 P t dependence do not agree with hydro The same P t dependence for pp, dau and AuAu Success of blast wave parameterisation Emission Function necessary in Hydro approach Proper treatment of resonances can solve a lot A consistent description urgently necessary NonGaussian shape analysis can be useful Particle correlations - a tool to verify our understanding...

11 RHIC HBT Puzzle Most reasonable models still do not reproduce RHIC at 130GeV HBT radii Hydro + RQMD STAR 130 GeV PHENIX 130 GeV π + π - Blast wave parameterization (Sollfrank model) can approximately describe data but emission duration must be small ρ 0 = 0.6 (radial flow) T = 110 MeV R = 13.5 ± 1fm (hard-sphere) τ emission = 1.5 ± 1 fm/c (Gaussian) PHENIX PRL (2002) from spectra, v 2

12 Theory

13 Thermal approach to RHIC W. Broniowski, W. Florkowski hep-ph/ One freeze-out Complete treatment of resonances

14 The RHIC HBT Puzzle Hinting at the solution Blast-wave parametrization Retiere and Lisa, nucl-th/ Longitudinal boost invariance Relative particle abundances not fixed Constant parameters at freeze-out Buda-Lund Hydro parameterization Csorgo et al, nucl-th/ Not boost invariant (Hubble flow) Freeze-out smeared in temperature R out (fm) R side (fm) R long (fm) s = 130 GeV STAR PHENIX Retiere, Lisa Csorgo et al k T (GeV/c)

15 Experiment

16 Role of Coulomb correction STAR - procedures Standard correction Dilution procedure Bowler-Sinyukov procedure: (born in Nantes by Sinyukov, Erazmus et al.)

17 Role of Coulomb correction STAR - preliminary

18 By T.Gutierrez and Z. Chajęcki p+p, d+au, Au+Au R out R out / R(fm) out (pp) R side R side / R(fm) side (pp) STAR - preliminary R R long (fm) long / R long (pp) All three systems exhibit similar k T dependence (?!)

19 Fourier coefficients of HBT(Φ) oscillations Out-of-plane sources at freeze-out Pressure and/or expansion time was not sufficient to quench initial shape From v 2 we know... Strong in-plane flow significant pressure build-up in system ε initial = ε final R y eccentricity R x STAR Collaboration, nucl-ex/ Short expansion time plays dominant role in out-of-plane freeze-out source shapes

20 Last minute results

21 Will be published in PRC M t dependence for positive and negative pion pairs STAR - preliminary 1. Excellent agreement for: (pi+) and (pi-) (The Coulomb interaction between outgoing charged pions and the residual positive charge is negligible.) 2. Increase of λ parameter: contribution of pions from long-lived resonances. 3. Decrease of radii: longitudinal and radial flow 4. Ro/Rs~1 short emission duration

22 Consistency of the results: STAR and PHENIX STAR - preliminary

23 New Coulomb corrections, open symbols STAR - preliminary

24 Non-identical particle correlations Study emission asymmetries with final-state interactions Strong radial flow induces species-dependent x-p correlations Case 1 Particle emitted closer to center is slower Case 2 Particle emitted closer to center is faster Effective interaction time Effective interaction time shorter larger Weaker correlation Stronger correlation The two cases can be discriminated Two correlation functions: lighter particle faster, lighter particle slower Compare correlation strength of two CF s...the idea born in Nantes by R. Lednicky, B. Erazmus et. a.

25 A. Kisiel for STAR Au+Au, s = 200 GeV pion slower pions C(pion faster) / C(pion slower) pion faster low β high β protons PRELIMINARY Blast-wave picture K pion faster shows stronger correlation π pions on average emitted nearer to source center Arises naturally in collective expansion picture Similar studies are underway for many particle combinations Exotic correlations like Ξ-π can yield information about nature of Ξ flow

26 Adam Kisiel Hydro inspired parametrization - radial flow produces asymmetry T = 110 MeV spectra trans. flow v = 0.6c - flow radius = 13 fm Unlike sign corr. Fctn like sign corr. fctn Unlike sign out ratio Like sign out ratio

27 Track Merging non-ident. (1) On the first glance track merging effects should not be present in non-identical analysis They are bended in opposite directions by the magnetic field However, it is also present in this kind of analysis

28 Hanna Gos Merging and anti-merging

29 Hanna Gos (pi+,pi-) - correlations

30 ALICE

31 4. Working chain for particle correlations Obtained results - what we have made already...

32 QS (quantum statistics) and FSI (final state interaction) weights for different two-particle systems (R. Lednicky) complete calculation of QS and FSI (Coulomb and strong), 6-dim. dependence: (p1x,p1y,p1z, p2x, p2y, p2z), possibility to introduce three body Coulomb effects, possibility to integrate bound state formation (deuterons). A table of two-particle systems for which the weight calculation is already prepared (The numbers correspond to the numbering in the computer code FSIW-LL )

33 Fits to 1D projections

34 Single event pion-pion interferometry by Hania GOS

35 CorrFit (fitting of correlation parameters) CorrFit is a tool developed in STAR by Adam Kisiel CorrFit is able to find parameters that fits correlation function taking to the account: Quantum Statistics Final State Interaction (Coulomb and strong) They are not for correction but are treated as a source of correlations! Detector resolution Can work with any model of the freeze-out distribution (Not limited to Gaussian source distribution!) Is able to fit non-identical particle correlation functions

36 Looking ahead towards LHC important contribution of hard processes Hard processes in Momentum Correlations Guy Paic and Piotr Skowroński Assumption: the source is a superposition of jet sources and a thermal fireball Then: the resulting correlations should reflect contributions from: 1. pairs of particles from a single jet dimension of the region where the jet fragmented, 2. pairs from different jets the size of the initial collision volume, 3. pairs where both particles come from the decupling thermal fireball, 4. pairs where one particle comes from the jet and the other from the thermal fireball. The simulations are in progress...

37 Thank you for your attention

38 L.Ray, QM 2002 Balance Function Widths for Au+Au at 200 GeV Narrows with centrality: - transverse boost - additional resonances(?) - late hadronization(?)

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