1. Spectator response to the participant blast in the reaction 197 Au+ 197 Au at 1 A GeV – results of the first dedicated experiment V. Henzl for CHARMS collaboration GSI, Planckstr. 1, 64291, Darmstadt, Germany (on leave from NPI Rez, Czech Republic) New tool for investigating the momentum- dependent properties of nuclear matter.

2. BUU calculations : 124 Sn + 124 Sn T lab = 800 MeV/u b = 5 fm L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001) T.Enqvist et al. NPA658(1999)47 M.V.Ricciardi et al. PRL 90(2003)212302 Fission events excluded !!! Idea Observation Vlad Henzl for CHARMS

3. BUU calculations : 124 Sn + 124 Sn T lab = 800 MeV/u b = 5 fm L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001) T.Enqvist et al. NPA658(1999)47 Idea Observation BUU by V.H. Vlad Henzl for CHARMS

4. Experiment at the Fragment Separator Once mass and charge are identified (A, Z are integer numbers) the velocity is calculated from B  => very precise determination! A/∆A ≈ 400 Inverse kinematics: From ToF:  /∆  ≈ 400  /∆  = B  / ∆ B  ≈ 2000 (36m) Vlad Henzl for CHARMS

5. Characteristics of the data unambiguous identification & precise longitudinal momenta limited acceptance: ±15mrad, ±1.5% in momentum only one fragment in one reaction measured Au+Au@1 A GeVPb+p@1 A GeV Vlad Henzl for CHARMS

6. Characteristics of velocity distributions 136 Xe+ nat Pb @ 1 A GeV (D.Henzlova) 197 Au+ 197 Au @ 1 A GeV (V.H.) limited momentum acceptance: Several magnetic field settings need to be combined to get complete velocity distribution Possible discrimination of fragmentation and fission Vlad Henzl for CHARMS

7.  single, predominantly largest residue per reaction unambiguously identified at FRS  mid-peripheral collisions investigated  the largest fragment is correlated with impact parameter (for Z max >30 ~ A max >65) fission excluded fission Information from 4π experiments 238 U+Cu 1AGeV - ALADIN Aladin data: Au+Au@400, 600, 800, 1000 AMeV Vlad Henzl for CHARMS

8. New experimental data, new simulations Vlad Henzl for CHARMS reacceleration observed for A res ≤ 85 BUU calculations with MD mean fields qualitatively agree with experiment (no sensitivity to stiffness of EoS) BUU calculations with static MI field are not able to describe trend of the data

9. Summary & Outlook 1) 197 Au+ 197 Au @ 500 A MeV (analysis in progress) 2) 197 Au+ 27 Al @ 500 A MeV (analysis in progress) 3) 112,124 Sn+ 112,124 Sn @ 1 A GeV (2005/2006) Outlook : Spectator response to the participant blast measured in Au+Au@1AGeV, reacceleration of the fragmentation residues observed for A res ≤ 85 only BUU with MD MF induce recovery of the fragment velocities with decreasing impact parameter, in qualitative agreement with the experiment Spectator response is a selective tool to access MD properties of MF further experiments needed to constrain MD properties of nuclear mean field Summary : Vlad Henzl for CHARMS