K. Wisniewski et al., Direct comparison of phase-space distribution of K- and K+ mesons in heavy-ion collisions at SIS energies - evidence for in-medium modifications of kaons?, EUR PHY J A, 9(4), 2000, pp. 515-519
The ratio of K- to K+-meson yields has been measured in the systems Ru-96 Ru-96 at 1.69 A GeV, Ru-96 + Zr-96 at 1.69 A GeV, and Ni-58 + Ni-58 at 1.9
3 A GeV incident beam kinetic energy. The yield ratio is observed to vary a
cross the measured phase space. Relativistic transport-model calculations i
ndicate that the data are best understood if in-medium modifications of the
kaons are taken into account.