Speaker
Description
The study of the density dependence of the equation of state (EOS) of nuclear matter at supra-saturation densities is a major topic of modern nuclear physics, with important implications in many fields. These span from astrophysics, such as the behavior of neutron stars and core collapse supernovae, to heavy ion collision (HIC) phenomena. Symmetry energy can be investigated not only by means of HIC, but also from astrophysical observations, including multimessenger astronomy combining gravitational waves and electromagnetic radiation observations. HIC at intermediate energies offer the opportunity to study nuclear matter at supra-saturation densities under controlled laboratory conditions. In this context, the ASY-EOS II experiment was performed at GSI, to constrain the symmetry energy of the EOS through measurements of neutron and proton elliptic flows, which are sensitive to the symmetry pressure during the high-density phase of the nuclear collisions. The ASY-EOS II experiment investigated ${}^{197}$Au+${}^{197}$Au reactions at beam energies of 280, 400, 600 and 1000 AMeV, employing several detector systems. The KRAB detector was used for multiplicity measurements and centrality selection and, together with the CHIMERA multidetector placed at forward polar angles, reaction plane reconstruction. The TOFD detector measured forward emitted fragments for the determination of impact parameter by means of global observables such as $Z_{max}$ and $Z_{bound}$. At 50 degrees the NeuLAND detector, dedicated to neutron and proton detection and vetoed by another TOFD double plane, allows neutron detection with high efficiency and granularity. Data analysis of the experiment is still ongoing: data reduction of CHIMERA and KRAB is advanced, with good reconstruction of the reaction plane and the impact parameter. Calibration of TOFD (veto) and NeuLAND is ongoing, with particular attention to neutrons and charged particle discrimination. Preliminary results of neutron and proton elliptic flow observables, currently in progress, will be shown.