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Bulk matter properties in RHIC collisions

Bulk matter properties in RHIC collisions. Outline. 3. 1. 2. Hadronic ratios. Resonance production. p T spectra. T c – Critical temperature for transition to QGP T ch – Chemical freeze-out ( T ch  T c ) : inelastic scattering stops

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Bulk matter properties in RHIC collisions

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  1. Bulk matter properties in RHIC collisions

  2. Outline 3 1 2 • Hadronic ratios. • Resonance production. • pT spectra. Tc – Critical temperature for transition to QGP Tch– Chemical freeze-out (Tch Tc) : inelastic scattering stops Tfo – Kinetic freeze-out (Tfo Tch): elastic scattering stops

  3. RHIC detectors designed for PID V0 decayvertices Ks p + + p - L  p + p - L  p + p + X-  L + p - X+L + p + W  L + K- Resonances in invariant mass spectra dE/dx in TPC STAR Preliminary Au+Au 40% to 80% 0 f0K0S  K*0 X+ Electron ID via p/E in EMC 0.2  pT  0.9 GeV/c Time of Flight (ToF) So far the RHIC experiments have published identified particle spectra for: p, p0, K, K0s, p, d, L, X± , W r0, f, D, h, K*0(892), S*(1385), L*(1520) D0, D±, J/Y’s(+ anti-particles) …

  4. A theoretical view of the collision 1 Chemical freezeout (Tch  Tc) : inelastic scattering stops

  5. What can Kaons tell us? Kaons carry large percentage of strangeness content. K- = us K+ = su Ratio tells about baryon transport even though not a baryon. Changing rapidity slice changes chemistry

  6. Models to evaluate Tch and B • Statistical Thermal Model • F. Becattini; P. Braun-Munzinger, J. Stachel, D. Magestro • J.Rafelski PLB(1991)333; J.Sollfrank et al. PRC59(1999)1637 • Assume: • Ideal hadron resonance gas • thermally and chemically equilibrated fireball at hadro-chemical freeze-out • Recipe: • GRAND CANONICAL ensemble to describe partition function  density of particles of species i • fixed by constraints: Volume V, , strangeness chemical potentialS,isospin • input: measured particle ratios • output: temperature T and baryo-chemical potential B Particle density of each particle: Qi : 1 for u and d, -1 for u and d si : 1 for s, -1 for s gi:spin-isospin freedom mi : particle mass Tch : Chemical freeze-out temperature mq : light-quark chemical potential ms : strangeness chemical potential gs : strangeness saturation factor Compare particle ratios to experimental data

  7. Centrality and Energy Dependence Close to net-baryon free Tch flat with centrality ● p, K,p ● p, K,p ● p, K,p, L, X ● p, K,p, L, X Close to chem. equilibrium ! STAR preliminary Au+Au at √sNN=200GeV and 62 GeV TLQCD~160-170MeV TLQCD~160-170MeV Energy dependence but small Nch dependence…

  8. Rapidity Dependence • Tch, gs • Small sensitivity to y • Close to strangeness equilibration in central collisions over y=0-3 (ybeam=6) • mq, ms • Reflect baryon density with y • Fit results • Mean • Upper/Lower error BRAHMS Au+Au 200 GeV

  9. (In)dependence of mid-rapidity yields Preliminary Preliminary • T, µB, and V can all vary with energy, but in such a way as to ensureyields stay ~constant Preliminary

  10. Results of Fit 200 GeV Au+Au Resonance Suppression 200 GeV p+p Strangeness Enhancement STAR Preliminary p+p particle ratios well described Au+Au only stable particle ratios well described

  11. How does volume affect production? • Canonical (small system i.e. p-p): Quantum Numbers conserved exactly. Computations take into account energy to create companion to ensure conservation of strangeness. Relative yields given by ratios of phase space volumes Pn/Pn’ = fn(E)/fn’(E) • Grand Canonical limit (large system i.e. central AA): Quantum Numbers conserved on average via chemical potential Just account for creation of particle itself. The rest of the system “picks up the slack”. When reach grand canonical limit strangeness will saturate. Not new idea pointed out by Hagedorn in 1960’s (and much discussed since)

  12. How can we observe this • Canonical suppression increases with increasing strangeness • Canonical suppression increases with decreasing energy • σ(Npart) / Npart = ε σ(pp) ε > 1 Enhancement!

  13. C to GC predicts a factor 4 - 5 larger X-enhancement at √sNN =8.8 GeV than at 17.3 GeV SPS at √s= 17.3 & 8.8 GeV NA57 (D. Elia QM2004) Yields don’t have time to reach limit – hadronic system? Temperature assumed is incorrect?

  14. And then at RHIC (200 GeV)... STAR Preliminary Au-Au √s=200 GeV p,K,p p,K,p,L,X L not flat any more! But does it over saturate or ONLY just reach saturation?

  15. Rcp of strange particles Baryons and mesons are different Rcp

  16. RAA of strange particles Phase space suppression in p+p vs jet suppression in Au+Au. h- Baryons with s quarks scale differently to non-strange.

  17. Is there a scaling? • The more strangeness you add the less it scales with Npart. Npart scaling Normalized to unity for 0-5% data

  18. Is there a scaling? • The more strangeness you add the less it scales with Npart. • The larger strangeness content scales better with Nbin. • Still not perfect. Nbin scaling Normalized to unity for 0-5% data

  19. s quarks have different scaling? • How about scaling according to quark content? u, d – scale with Npart – already observed. s – scale with Nbin – appears better for strange particles. • K0s – 1/2*Npart + 1/2*Nbin • p – Npart • L – 2/3*Npart + 1/3*Nbin • – 1/3*Npart + 2/3*Nbin • f – Nbin • W – Nbin Pretty good! Does strangeness “see” a different correlation volume? f – Npart

  20. A theoretical view of the collision 2 Chemical freezeout (Tch ) ~ 170 MeV Time between Tch and Tfo

  21. Resonance survival probability  K* lost  K K*   K* K K K measured • Initial yield established at chemical freeze-out • Decays in fireball mean daughter tracks can rescatter destroying part of signal • Rescattering also causes regeneration which partially compensates • Two effects compete – Dominance depends on decay products and lifetime  lost K* K measured Kinetic freeze-out Chemical freeze-out time Ratio to “stable” particle reveals information on behaviour and timescale between chemical and kinetic freeze-out

  22. Resonance ratios Thermal model [1]: T = 177 MeV mB = 29 MeV UrQMD [2] K*rescatt. > regen. L* rescatt. > regen. D++ rescatt. < regen. S* rescatt. < regen. Need >4fm between Tch and Tfo [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 Small centrality dependence: little difference in lifetime!

  23. A theoretical view of the collision 3 1 2 Chemical freezeout (Tch ) ~ 170 MeV Time between Tch and Tfo 4fm Kinetic freeze-out (Tfo Tch): elastic scattering stops

  24. Hydro-dynamical model Fit range : mT – mass < 1 GeV/c2 bs R Shape of the mT spectrum depends on particle mass Two Parameters: Tfo and b Lattice QCD: Tc = 17010 MeV Tch PHENIX Au-Au 200 GeV E.Schnedermann et al, PRC48 (1993) 2462 r =s(r/R)n STAR Preliminary Tfo ~110MeV, <  > = 0.8 c

  25. Multi-strange Kinetic Freeze-out Tdec = 100 MeV Kolb and Rapp,PRC 67 (2003) 044903. • , K, p: Common thermal freeze-out at Tfo ~ 90 MeV <> ~ 0.60 c • : Shows different thermal freeze-out behavior: Tfo ~ 170 MeV <> ~ 0.45 c Blastwave parameterization Higher temperature Lower transverse flow Probe earlier stage of collision? • Hydro does not need different T for multi-strange • Freeze-out T different – Is blastwave realistic? Are re-interactions till freeze-out realistic either?

  26. p+p is not trivial

  27. pT spectra vs multiplicity 1) Re-bin and Divide by min.bias 2) Scale by:<NMB>/ <Nk> L high mult. spectra are more enhanced at high pT then K0s → More contribution of Minijets ??

  28. Summary • Appear to have strangeness saturation at most central top RHIC energies but not before (gs = 1). • Do s quarks “see“ a different correlation volume to light quarks? • There is a rescattering between Tch and Tfo. • There is strong radial flow in Au-Au system. • Seems that X and W freeze-out differently. • 62.4 GeV rather similiar to 200 GeV Our simple thermal pictures are only approximately correct. The devil is in the details but we have the data to figure it all out.

  29. Backup from here

  30. What happens to other particles? p – Npart scaling p – slight increase phase space suppression of baryons? K0s – only small phase space suppression of strange mesons? Not flat with centrality Containss and s quark, so not strange should show no volume dependence What about thef? factor 2 increase relative to p-p

  31. from BaBar

  32. Scale: (Nud/Nq)*Npart + (Ns/Nq)*Nbin Scale: (Nud/Nq)*0.5*Npart + (Ns/Nq)*Nbin

  33. SIS energies KaoS M. Mang et al. C: N ~ V2 (V 0) GC: N ~ V (V ) Assume V ~ Npart Pions/Apart constant grand-canonical! Kaons/Apart rising canonical! J. Cleymans, H. Oeschler, K. Redlich, PRC 59 (1999)

  34. Seems OK at SPS too Again not bad except for peripheral bin - errors large. Normalized to unity for 0-5% data

  35. Thermal model reproduced data Created a Large System in Local Chemical Equilibrium Data – Fit (s) Ratio Do resonances destroy the hypothesis? Used in fit

  36. Constraining the parameters

  37. How about at SPS? Again : • The more strangeness the less the particle scales with Npart. • Nbin scaling not correct either. • u,d vs s quark scaling, not bad except for most peripheral bin - errors large. Npart scaling Nbin scaling Normalized to unity for 0-5% data

  38. RAA of strange particles h- K±, K0s, f and h- all scale similarly p, L, X show hierarchy. Phase space suppression in p-p fighting jet suppression in Au-Au.

  39. Flow Effect on Spectra Flow increases as centrality increases PHENIX, STAR Preliminary 200 GeV p

  40. Baryon transport to mid-rapidity Clear systematic trend with collision energy • B - all from pair production • B - pair production + • transported from ybeamto y=0 • B/B ratio =1 - Transparent collision • B/B ratio ~ 0 - Full stopping, little pair production Preliminary L/L • ~2/3 of baryons from pair production • First time pair production dominates • Still some baryons from beam

  41. Au-Au p-p Collective motion in Au-Au data data / power law not absolute mT scaling... but if you rescale not in Au-Au

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