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

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

Au+Au C+C

Creation of Strange Mesons uduudu  uuuu  udsuds susu p K-K- K - absorption uduudu uduudu n p uddudd susu K+K+ susu p KK dduddu n udsuds n p uddudd susu  K+K+ dduddu n uduudu udsuds n dudu  uddudd susu  K+K+

Mean free path of Kaons and Antikaons K + : "nearly" undisturbed messengers mean free path at ρ 0 : λ(π) = 0.3 fm λ(K + ) = 5 fm λ(K - ) = 0.8 fm K - absorption by strangeness exchange reactions: K - p → Y π o

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

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

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

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

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

Kaon Spectra PRC 75 (2007)

Trend of the K + slopes

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

Slopes of K - are lower!

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

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

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

IQMD Calculations (C. Hartnack et al.)

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

Latest from KaoS: v 2 as a function of p t Au+Au 1.5 AGeV, M. Ploskon, KaoS to be published! IQMD calculations, C. Hartnack

T. Gaitanos et al., EPJ A12, 421 (2001) The nuclear equation of state Densities reached in Au+Au ≈ 2-3 ρ 0, in C+C much less

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)

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

K + yield determined at production which is around twice ρ 0 K + spectra dominated by scattering, some influence by KN potential K - yield dominated by strangeness exchange at densities around ρ 0 K - spectra influenced by absorption, scattering and potential

Best observable for KN Potential? K + yield K - yield K - /K + ratio Difference in slopes Spectra at low momenta v 2 (K + ) v 2 (K - ) * - ** * (*) * ? Input ? Input, K +, pi, … Same only K + cancels K + rescattering K - decay Difficult to measure Contribution of rescatt.? Emission time and potential(?) K + ( AuAu )/K + ( CC ) * * * EOS! Most uncertainties cancel

Grazie!