Impact of the in-medium conservation of energy on the π-/π+ multiplicity ratio.

An upgraded version of the isospin dependent Tübingen QMD transport model, which allows the conservation of the total energy, is presented. This is achieved by including in the energy-balance equations of the density, isospin asymmetry and momentum dependent inmedium baryon potential energies. It leads to an effective modification of particle production thresholds with respect to the vacuum ones. Compatible constraints for the symmetry energy stiffness from π-/π+ multiplicity ratio and elliptic flow experimental data of Au+Au collisions at 400 MeV/nucleon can be extracted in this case. However, an important dependence of the π-/π+ observable on the strength of the isovector part of the Δ(1232) isobar potential is also demonstrated. [ABSTRACT FROM AUTHOR]