Helmut Oeschler Darmstadt University of Technology

1. Strangeness Production at 1 -2 AGeV Helmut Oeschler Darmstadt University of Technology Erice, September 2008

2. Results mainly from the KaoS Collaboration Phys. Rev. C (2007) Detailed IQMD Calculations Phys. Rep. in preparation withC. Hartnack, J. Aichelin

3. Au+Au C+C

4. u d s L u d u u d d p u d d n n s u s u K+ K+ s u u d u K- u d u d d u p p n d d u n u d s u d u u d d u d s p S0 L n u u s u d u s u K- p0 K+ p+ K-absorption Creation of Strange Mesons

5. Mean free path of Kaons and Antikaons mean free path at ρ0: λ(π) = 0.3 fm λ(K+) = 5 fm λ(K-) = 0.8 fm K- absorption by strangeness exchange reactions: K- p → Y πo K+: "nearly" undisturbed messengers

6. K+ production below and at threshold Comparision with data IQMD calculations, Au+Au central collisions

7. Before getting started: Are the pions okay? Data: A. Wagner et al., KaoS N/Z ratio and Coulomb

8. KaoS Collaboration, PRC 75 (2007) K- and K+ are linked Is s exch. in equil.? Law-of-mass action J. Cleymans et al., PLB 603(2004) M ~ Aγ A. Förster, F. Uhlig et al., PRL 91 (2003)

9. IQMD C. Hartnack et al., PRL 93 (2004)

10. Time Evolution of K+ and K- Production Strangeness exchange dominates! Only 20% of all K- survive! C.Hartnack, H.O., J. Aichelin, PRL 90(2003)

11. Kaon Spectra PRC 75 (2007)

12. Trend of the K+ slopes

13. What determines the shape of the K+ spectra? According to IQMD calculations

14. Slopes of K- are lower!

15. Influence on K- spectra Au+Au: only 20% survive about 30% of those do not scatter

16. K+ yield determined at production K+ spectral shape at last collision K- yield and spectral shape at last collision

17. Out-of-plane Emission Ni+Ni 1.93 AGeV (F .Uhlig, PRL 95 (2005))

18. IQMD Calculations (C. Hartnack et al.)

19. F. Uhlig, et al., KaoS, PRL 95 (2005)

20. Latest from KaoS: v2 as a function of pt Au+Au 1.5 AGeV, M. Ploskon, KaoS to be published! IQMD calculations, C. Hartnack

21. T. Gaitanos et al., EPJ A12, 421 (2001) The nuclear equation of state Densities reached in Au+Au ≈ 2-3 ρ0, in C+C much less

22. KaoS Collaboration C. Sturm et al., PRL 86 (2001) A.Förster et al., PR C75 (2007) RQMD: C. Fuchs et al., PRL 86 (2001) IQMD: C. Hartnack et al., PRL 96 (2006)

23. Results confirmed also with several calculations and other observables! C. Hartnack, HO, J. Aichelin, PRL 96 (2006)

24. K+ yield determined at production which is around twice ρ0 • K+ spectra dominated by scattering, some influence by KN potential • K- yield dominated by strangeness exchange at densities around ρ0 • K- spectra influenced by absorption, scattering and potential

25. Best observable for KN Potential? K+(AuAu)/K+(CC) * * * EOS! Most uncertainties cancel

26. Grazie!