Exploring hot and dense QCD matter with HADES

Abstract

Abstract Experiments at snn s NN = 2 − 3 3 GeV provide the lowest energy point of the global effort made by the heavy-ion community in order to map the QCD phase diagram. This correspond to the highest baryon chemical potential, 700-900 MeV according to the universal freeze-out curve, and temperatures of the fireball of 60-80 MeV. The formed matter can be characterized in terms of particle spectra, fluctuations and correlations. The dilepton spectrum is dominated by thermal emission from the medium and it is sensitive to in medium hadron properties. Strangeness production occurs below the free nucleon-nucleon threshold and it is a sensitive probe to test models of strangeness propagation in matter and its coupling to baryons. Data show a common scaling of measured yields as a function of number of participating nucleons independently on the strangeness content or mass of the hadron. Strangeness propagation in cold nuclear matter produced in pion induced reactions on heavy and light targets shows a significant absorption of negative kaons in heavy targets as well as a similar behaviour of ϕ indicating a strong coupling of ϕ with nucleons. Two-pion correlations, flow harmonics, fluctuations are explored as well in order to further pin down the properties of the created matter.