  Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport
model, the isotope Sn+Sn reactions at 270 MeV/nucleon are investigated. It is
shown that nucleon and meson observables in the Sn+Sn reactions at 270
MeV/nucleon cannot effectively probe the high-density symmetry energy. These
observables, however, are sensitive to the curvature of the symmetry energy. It
thus sheds light on the study of the high-density behavior of the nuclear
symmetry energy by extracting the curvature of the symmetry energy through the
interpretation of forthcoming RIBF/RIKEN related data.
