Investigation of subthreshold K + and K - production what remains from the KN potentials?
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Investigation of subthreshold K+ and K- production
what remains from the KN potentials?C.Hartnack and J. Aichelin
SUBATECH, Ecole des Mines & CNRS & University, Nantes (France)
Outline: ● The IQMD model and its KN potentials● Comparison to KaoS Data● Slope of K+ and K- spectra● Influence of potentials and rescattering● Influence of channels and production times● Conclusion
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The IQMD model
● Semiclassical microscopic model on an event by event basis● Full time-evolution of each event allows for a view inside the reaction● Includes nucleons, deltas , pions with their isospin degrees of freedom● Nuclear eos, Coulomb, asymmetry, Yukawa and momentum dep. pot.● Virtual treatment of strange particles allows for high statistics● KN optical potential
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KN optical potential
Parametrisation :RMF calculations of J. Schaffner-Bielich
Attention: K- production process via hyperons may involve
K+ and K- potentials for K- production
K- pot.
K+pot
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Comparison to KaoS DATA
● Calculations in good agreement with data by A.Foerster● KN potential penalizes K+ and K- production
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Comparison of slopes for K+ and K-
● KaoS claims different slopes of K+ and K- but measures only limited momentum range ● K+ from IQMD show different slopes at low and high p
4π
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Influence of potential and rescattering
● No influence of K+ potentials on the slope ● Rescattering influences high energy tail
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Influence of potential on K- spectra
● Only K+ potential influences the K- slope: reduced production of hyperons● K- potential effect only at very low energies
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Analysis of the production time
K+ are produced in the high density phase while surviving K- stem from later times
Definition of 3 time windows
early t< 8fm/c
mid 8<t<16fm/c
late t> 16fm/c
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Time windows for K+
● Strong contribution of early times● Similar time profile for all channels
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Time windows for K- spectra
● Slope depends on production time● Different channels show up at different times
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Contribution of different channels
● K+ : no strong difference in slopes● K- : Different slopes for π–Y and B-Y
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Conclusion
● K+ spectra show different slopes at low and high momenta
● KN-potentials show little effects on slope of K+ ● K- spectra are only slightly influenced by K- potentials
● B-Y and π-Y induced K-reactions:1) Appear at different times2) Show different slopes3) Consequently: the experimental slope allows to get
information on the production channels but not on the KN potentials
● Importance of the reaction dynamics for understanding the slopes of the spectra
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Appendix (or stuff that you will only see if you really ask for it)
● K+ spectra, centrality dependence● K- spectra, centrality dependence ● K- spectra, influence of absorption ● cos() K+ to K-, K+ potential and rescattering● cos() K- potential and absorption● cos() K+ time-window, channels, centrality● cos() K- time-window, channels, centrality ● K+ K- azimuthal distributions at midrapidity● K+ K- azimuthal distributions: potential● K+ K- azimuthal distributions: rescattering ● Souvenirs of SQM 2001
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Centrality dependence K+ spectra
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Centrality dependence K- spectra
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Influence of K- absorption
● Suppression of absorption recovers many K- produced in early times ● Influence especially at low momenta
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K+ cos() distributions
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K- cos() distributions
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K+ cos() distributions
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K- cos() distributions
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K+&K- azimuthal distributions
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K+ & K- azimuthal dist.: potential
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K+ & K- azimuthal dist.: rescattering
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Souvenirs from SQM 2001
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Influence of KN potentials