Measurement of the Response of the Spectators to the Participants Blast M. V. Ricciardia, T. Enqvista,[1], J. Pereirab, J. Benlliureb, M. Bernasc, E. Casarejosb, V. Henzla, A. Kelića, J. Taiebc,[2], K.-H. Schmidta   aGSI, Planckstr. 1, 64291, Darmstadt, Germany bUniversity of Santiago de Compostela, 15706 Santiago de Compostela, Spain cInstitut de Physique Nucléaire, 91406 Orsay Cedex, France [1] Present address: University of Jyväskylä, 40351 Jyväskylä, Finland [2] Present address: CEA/Saclay DM2S/SERMA/LENR, 91191 Gif/Yvette CEDEX, France

Motivation BUU calculations : 124Sn +124Sn Tlab= 800 MeV/u b = 5 fm L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001) The surviving spectator is influenced by the blast of the participants Response of the spectators is ruled by the properties of the nuclear matter (=> EOS) !!!

The experiment at the Fragment Separator, GSI-Darmstadt Once mass and charge are identified (A, Z are integer numbers) the velocity is calculated from B => very precise evaluation!

Velocity distributions of fragmentation residues 238U+Pb (dashed line) 238U+Ti (full lines) T.Enqvist et al. NPA658(1999)47 M.V.Ricciardi et al. submitted to PRL

Mean velocities of fragmentation residues T.Enqvist et al. NPA658(1999)47 M.V.Ricciardi et al. submitted to PRL Indications for the postulated response of the spectators to the participant blast. Precise velocity measurement of projectile fragments is a new tool to investigate the EOS of nuclear matter

The epilogue: “What can we learn from the spectators?” Theoretical calculations: (Shi, Danielewicz, Lacey) Change of the net momentum (NM) depends on momentum dependence of the nuclear mean field (MF) Dependence of NM change on stiffness of EOS very small Different reaction systems => different response