1. Helmut Oeschler Darmstadt University of Technology Transition from Baryonic to Mesonic Freeze Out SQM2006, March 28 th, 2006

2. 1.Experimental observation of maximal strangeness content around 30 A GeV comparison with Statistical model NPA 697(2002) 902 2.Freeze-out condition changes Phys. Lett. B615 (2005) 3.Possible deviation from usual freeze out around 30 A GeV? 4.Strangeness content of a ``corresponding´´ QGP

3. Chemical Freeze Out J. Cleymans and K. Redlich, PRL 81 (1998) 5284

4. Baryons Stat. Mod. : All exhibit maxima, but at different locations

5. Mesons Stat. Mod. : Only K + /π + exhibits a maximum!

6. Maximum Strangeness around 30 AGeV P. Braun-Munzinger, J. Cleymans, HO, K. Redlich, NPA 697(2002) 902 λ S = 2 sŝ/(uū+ dđ)

7. Transition from baryonic to mesonic freeze out entropy prop to T 3 J. Cleymans, H.O., K. Redlich, S. Wheaton, Phys. Lett. B615 (2005) Meson dominated Baryon dominated

8. Transition At this transistion the freeze out condition is changing! Deviations from the simple unique freeze out possible?

9. S.Wheaton,

10. S. Wheaton et al., to appear

11. Freeze-Out Volume from HBT D. Adamova et al., CERES, PRL 90 (2003) √ √

12. K - /K + Ratio from SIS up to RHIC

13. T(K - ) < T(K + ) at 1 – 2 A GeV A.Förster, KaoS Collab., PRL 91 (2003) 152301 K+K+ K-K-

14. Strangeness Content A. Schmah et al., TU Darmstadt Hadron gasIdeal gas of quarks NPA 697(2002) 902

15. Why do we observe the strangeness content of a Hadron Gas and not of a Quark Gluon Plasma?

16. R.V. Gavai and S. Gupta, PRD 65 (2002) 094515 λ s ~ χ S / χ u

17. Observation qualitatively agree with Stat. Model. But deviations are seen! Different location of maxima as a test? Early freeze out of K + ? Would increase its yield! Equilibrated quark gas would give a very high yield of strangeness! Thank you!

19. Expected Centrality Dependence (SM) Pion density n(π) = exp(-E π /T) Strangeness is conserved! Kaon density NN N Λ K + n(K) = exp(-E K /T) [g V ∫ … exp[-(E Λ -µ B )/T] J. Cleymans, HO, K. Redlich, PRC 60 (1999)

20. Qualitative agreement! Except for AGS!

21. AGS Au+Au 6 A GeV P. Chung et al., E895 Coll. PRL 91(2003) Updated M ~ (A part ) α

22. All these observation agree with a hadron gas at chemical equilibrium What did we learn? Many arguments that „QGP“ has been formed. 1.What dynamics causes freeze out? 2. Where do we observe quark degrees?

23. Strangeness Enhancement Data: WA97 New: NA57 Theory: S. Hamieh, K. Redlich A. Tounsi, PL B486 (2000) 61 Strangeness enhancement as a signal of QGP? Canonical strangeness suppression?

24. λ S = 2 sŝ/(uū+ dđ)

25. SIS: nuclear EoS, K + and K - : Different freeze out K - via strangeness exchange SIS and AGS: Strangeness exchange important Ξ at 6 AGeV yield in agreement with Stat. Mod. Max. strangeness content around 30 AGeV Transition from Baryonic to Mesonic Freeze Out RHIC: Statistical model works very well LHC:?

26. SIS: nuclear EoS, K+ and K-: Different freeze out A. Förster et al.,(KaoS Coll.) PRL 91 (2003) SIS and AGS: Strangeness exchange important J. Cleymans et al., PLB 603 (2004) Transition from Baryonic to Mesonic Freeze Out J. Cleymans et al., Phys. Lett. B 615 (2005) RHIC: Statistical model works very well And beyond!

27. At LHC particle production will be dominated by hard processes! Jets! Will this destroy the simple picture (SM)? More strangeness due to faster decay from the QGP? Less strangeness due to fragmentation? Will one observe a hadronic composition in jets as expected from the two parameters T and μ B ? Interesting already in pp collisions … v2, jet quenching, heavy flavor,…

28. P. Braun-Munzinger, J. Cleymans, HO, K. Redlich, NPA 697(2002) 902

31. Do the slopes make a consistent picture? Ni+Ni 1.93 AGeV F. Uhlig, TU DA Diss. Protons, K + and pions cross K - differ! T(stat. Model) = 74 MeV PRC 59 (1999)

32. Transition

33. √

34. A. Mischke, Ph.D. thesis

36. Statistical Model P. Braun-Munzinger, D. Magestro, K. Redlich, J. Stachel, PL B518 (2001) updated

37. Statistical Model

38. Statistical Model for SIS J. Cleymans, H. O., K. Redlich, PRC 59 (1999)

40. Dynamics of K + and K - K + yield established early by the high-density phase, not changed due to s-conservation (K + from the interior) K + slopes (and angular distributions) dominated by rescattering K - yield established late by Λ and π concentration (K - from the surface) Even if K - from a thermal source of Λ and π, T(K - ) is smaller than T(source). Only those K - are observed which did NOT had an interaction Stat. Model describes the ratios, but does not describe T(K - ).

42. K - and K + are linked Au+Au and Ni+Ni 1.5 AGeV A. Förster, F. Uhlig et al., KaoS PRL 91 (2003) 152301 dashed line: stat. Model K - and K + are linked via strangeness exchange Λ π -> K - N „Law of mass action“ J. Cleymans, et al. PLB603(2004)

43. Maximum around 30 A GeV