Differential neutron-hydrogen squeeze-out

The equation of state (EOS) of asymmetric nuclear matter is of fundamental importance to both nuclear physics and astrophysics. While considerable progress has been made recently in determining the symmetry energy around normal nuclear matter density [1], much more work is still needed to probe its high-density behaviour. This requires reaction studies at sufficiently high energies and probes sensitive to mean-field effects in the initial compressed stage of the reaction as, for example, the neutron-proton differential transverse and elliptic flows [2]. In two experiments at GSI using the LAND and FOPI detectors, both neutron and hydrogen collective flow observables from Au + Au collisions at 400, 600 and 800A MeV have been measured [3]. This data set is presently being reanalyzed in order to determine the optimum conditions for a dedicated differential flow experiment, but also with the aim to produce first results from a comparison with state-of-the-art transport models. In the following, we present results obtained with the UrQMD model which has recently been adapted to heavy ion reactions at intermediate energies [4].