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Using strange hadron yields as probes of dense matter.

This study explores the use of strange hadron yields as probes of dense matter. It investigates the applicability of thermal models, the description of multiplicity trends, and the extension of bulk effects into the high pT regime. The study also examines the predictions made by different models and their consistency with experimental data.

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Using strange hadron yields as probes of dense matter.

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  1. Using strange hadron yields as probes of dense matter. Outline • Can we use thermal models to describe the data? • Can we describe the multiplicity trends? • How do the bulk effects extend into the high pT regime?

  2. Models readily available to experimentalists

  3. First make a consistency check • Require the models to, in principle, be the same. • Only allow the least common multiple of parameters: T, q, s, s • Use Grand Canonical Ensemble. • Fix weak feed-down estimates to be the same (i.e. at 100% or 0%).

  4. The results Au-Au √sNN = 200 GeV after feed-down increase s decrease T 1  error Similar T and s Significantlydifferent errors. Not identical and feed-down really matters

  5. “Best” predictions (with feed-down) 0-5% Au-Au √sNN = 200 GeV STAR Preliminary

  6. Comparison between p-p and Au-Au Au-Au √sNN = 200 GeV STAR Preliminary p-p √s = 200 GeV STAR Preliminary Canonical ensemble

  7. Centrality dependence Solid – STAR Au-Au √sNN = 200 GeV Hollow - NA57 Pb-Pb √sNN = 17.3 GeV STAR Preliminary We can describe p-p and central Au-Au average ratios. Can we detail the centrality evolution? Look at the particle enhancements. E(i) = YieldAA/Npart Yieldpp /2

  8. Centrality dependence STAR Preliminary • Use stat. model info: • C – p-p • Strangeness suppressed • GC – central A-A • Strangeness saturated • Transition describes • E(i) behaviour • T =170-165 MeV • assume same T for p-p and Au-Au Au-Au √sNN = 200 GeV K. Redlich

  9. Varying T and R Au-Au √sNN = 200 GeV Calculation for most central Au-Au data Correlation volume: V0  R03 R0 ~ proton radius strong interactions Rapid increase in E(i) as T decreases SPS data indicated R = 1.1 fm K. Redlich

  10. Centrality dependence Correlation volume: V= (ANN)·V0 ANN = Npart/2 V0 = 4/3 p·R03 R0 = 1.1 fm proton radius/ strong interactions STAR Preliminary T = 170 MeV T = 165 MeV Au-Au √sNN = 200 GeV Seems that T=170 MeV fits data best – but shape not correct K. Redlich

  11. Npart dependence Correlation volume: V= (ANN)a·V0 ANN = Npart/2 V0 = 4/3 p·R03 R0 = 1.2 fm proton radius/ strong interactions STAR Preliminary T = 165 MeV a = 1/3 T = 165 MeV a = 1 T = 165 MeV a = 2/3 Au-Au √sNN = 200 GeV Seems to be a “linear” dependence on collision geometry K. Redlich

  12. More on flavour dependence of E(i) STAR Preliminary STAR Preliminary PHOBOS: measured E(ch) for 200 and 19.6 GeV Enhancement for all particles? PHOBOS: Phys. Rev. C70, 021902(R) (2004) Au-Au √sNN = 200 GeV Yes – not predicted by model Similar enhancement for one s hadrons

  13. Can we describe √s dependence? PHOBOS: Phys. Rev. C70, 021902(R) (2004) There’s a correlation between dNch/dh and Npart/2 small dotted lines are: dNch/dh = npp(1-x)Npart/2 + xNbin npp= Yield in pp = 2.29 ( 1.27) x = 0.13 N.B.: SPS energy only 17 GeV If know npp can predict yield at any Npart

  14. Strangeness and dNch/dh Solid – STAR Hollow – NA57 STAR Preliminary Look at yields relative to pp SPS and RHIC data follows similar curves as a func. of dNch/dη at mid-rapidity NA57 dNch/dη (pBe) =1.64 STAR dNch/dη (pp) =2.12 Entropy alone seems to drive much of the soft physics

  15. RAA – Beyond the bulk √sNN = 200 GeV Canonical suppression in p+p? √sNN = 200 GeV STAR Preliminary Rcp  Raa Effect increases as strange content of baryon increases.

  16. RAA for central and peripheral data Au-Au √sNN = 200 GeV STAR Preliminary Au-Au √sNN = 200 GeV STAR Preliminary Peripheral and central data both show an enhancement Peripheral data is more enhanced – Cronin effect?

  17. RAA - A mocked upstring picture does well Are strong color fields the answer? HIJING/BBar + KT ~ 1 GeV Strong Color Field (SCF) qualitatively describes RAA. SCF - long range coherent fields SCF behavior mimicked by doubling the effective string tension Topor Pop et al. hep-ph/0505210 SCF only produced in nucleus-nucleus collisions RAA≠ RCP

  18. Nuclear modification factors - RCP √sNN=62 GeV 0-5% 40-60% 0-5% 40-60% √sNN=17.3 GeV NA57, PLB in print, nucl-ex/0507012 √sNN=200 GeV First time differences between L and L B absorption? Recombination or different “Cronin” for L and K at SPS?

  19. The Rcp double ratio NA57: G. Bruno, A. Dainese: nucl-ex/0511020 Baryon/meson splitting at SPS and RHIC is the same 62 GeV Au+Au data also follows the same trend Recombination present in all systems? STAR Preliminary What about other centralities?

  20. Conclusions • Not all thermal models are the same – even when you try and make them so. • The enhancement of strangeness as a function of centrality CAN be described– scales with Npart 1/3 NOT Npart • Non-strange particles are enhanced – NOT predicted by phase space models. • Using dNch/dη better than Npart. This is a physical observable unlike Npart. • The phase space effects of p-p extend into high pT regime. • Baryon/meson splitting energy independent.

  21. Multiplicity scaling with log(√s) If I can describe dNch/dh as function of√s dNch/dη- strongly correlated to the entropy of the system! Can we describe other observables in terms of dNch/dη? PHOBOS White Paper: Nucl. Phys. A 757, 28, nucl-ex/0410022

  22. HBT and dNch/dh HBT radii ~linear as a function Npart1/3 Even better in (dNch/dh)1/3 power 1/3 gives approx. linear scale Scaling works across a large energy range nucl-ex/0505014 M.Lisa et al.

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