ENTROPY IN CENTRAL AU+AU REACTIONS BETWEEN 100 AND 400A MEV

The ratio of the total charge bound in fragments with Z between 2 and 15 to the hydrogen yield, (Sigma(2)(15) M(i)Z(i))/M(H), has been measu red, and the neutron-to-proton ratio n/p has been estimated from the d ata of central Au + Au reactions between 100 and 400 A MeV, measured w ith the phase I setup of the detector system FOPI at the GST, Darmstad t, in the polar-angle range between 7 degrees and 30 degrees. These tw o quantities were used to determine the entropy per nucleon S/A by com paring them with the predictions of the FREESCO code. The analysis all ows the simultaneous extraction of the values of the baryonic entropy, temperature, and collective how. The extracted values are in good agr eement with the values obtained in earlier FOPI studies and, for the b aryonic entropy, with recent hydrodynamic calculations.