Isolation of the nuclear compressibility with the balance energy

Previous theoretical studies of the disappearance of directed transverse flow showed a dual dependence on the equation of state (EOS) and the in-medium cross section (sigma(nn)) for light systems. Also, the balance energy was shown to increase as a function of the impact parameter. However, Boltzmann-Uehling-Uhlenbeck (BUU) model calculations show that the dependence on sigma(nn) weakens for heavy systems such as Au+Au, and data presented here show that the impact parameter dependence nearly vanishes for Au+Au. Therefore, the EOS parameter K can be isolated using the balance energy, and BUU calculations show good agreement for a soft EOS. The reduction in sigma(nn) is then investigated using the experimental mass dependence of the balance energy.