From Stopping to Viscosity in Heavy Ion Collisions

Stopping in heavy ion collisions is investigated with the aim of learning about the shear viscosity of nuclear matter. Boltzmann equation simulations are compared to available data on stopping in the energy range of 20 - 117 MeV/nucleon. Stopping observables used include momentum anisotropy and linear momentum transfer. The data show that modeling the transport with free nucleon-nucleon cross-sections is inaccurate and reduced cross-sections are required. Reduction of the cross-sections produces an increase in the shear viscosity of nuclear matter, compared to calculations based on free cross-sections.