Kaon and pion production in nuclear collisions

Kaon production has been studied in proton-nucleus, deuteron-nucleus, alpha-nucleus and in symmetric nucleus-nucleus collisions at bombarding energies above and below the K"+ production threshold for free NN collisions. The K"+ double differential cross section measured in p+C collisions at 2.5 GeV beam energy can be explained by kaon production in first chance nucleon-nucleon collisions with the target nucleon having a momentum-energy distribution according to the nuclear spectral function. The K"+ production cross section measured in p+C and p+Pb collisions at 1.2 and 1.5 GeV beam energy exceeds the prediction of the first chance collision model by a factor of 5 to 10. The projectile and target dependence of K"+ and #pi#"+ production as measured in d+C, d+Pb, #alpha#+C and #alpha#+Pb collisions at 1.15 AGeV yields evidence for K"+ production via collisions of high energetic pions with nucleons. In Au+Au collisions at 1 AGeV the K"+ multiplicity per participating nucleon increases with increasing number of participating nucleons. The azimuthal emission pattern and the inverse slope parameter of K"+ mesons and high energetic pions are a hint for a simultaneous freeze-out of these particles during the hot and dense phase of the collision. Transport calculations have to assume a soft equation of state in order to reproduce the measured K"+ cross sections. The in-medium K"-cross section measured in Ni+Ni collisions is enhanced by a factor of 7#+-#3 as compared to the free cross section when using the K"+ cross section at equivalent beam energies as a normalization. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman