Circumstantial evidence for a soft nuclear symmetry energy at supra-saturation densities

Zhigang Xiao, Bao-An Li, Lie-Wen Chen +2

Within an isospin- and momentum-dependent hadronic transport model it is shown that the recent FOPI data on the ${\pi }^{-}/{\pi }^{+}$ ratio in central heavy-ion collisions at SIS/GSI energies…