Hadronic matter is soft.
The stiffness of the hadronic equation of state has been extracted from the production rate of K+ mesons in heavy-ion collisions around 1 AGeV incident energy. The data are best described with a compression modulus K around 200 MeV, a value which is usually called "soft." This is concluded from a detailed comparison of the results of transport theories with the experimental data using two different procedures: (i) the energy dependence of the ratio of K+ from Au+Au and C+C collisions and (ii) the centrality dependence of the K+ multiplicities. It is demonstrated that input quantities of these transport theories which are not precisely known, such as the kaon-nucleon potential, the deltaN --> NK+lambda cross section, or the lifetime of the delta in matter, do not modify this conclusion.
Hartnack
Ch
Ch
SUBATECH, Laboratoire de Physique Subatomique et des Technologies Associées, University of Nantes-IN2P3/CNRS-Ecole des Mines de Nantes, 4 rue Alfred Kastler, F-44072 Nantes CEDEX 03, France.
Oeschler
H
H
Aichelin
Jörg
J