1. Response of the Spectators to the Participants Blast as a Probe of the Momentum-Dependent Nuclear Mean Field V. HENZLa, M. V. Ricciardia, T. Enqvista,[1], J. Pereirab, J. Benlliureb, M. Bernasc, E. Casarejosb,, A. Kelića, J. Taïebc,[2], K.-H. Schmidta, aGSI, Planckstr. 1, 64291, Darmstadt, Germany, bUniversity of Santiago de Compostela, Santiago de Compostela, Spain, cInstitut de Physique Nucléaire, Orsay Cedex, France [1] Present address: University of Jyväskylä, Jyväskylä, Finland, [2] Present address: CEA/Saclay DM2S/SERMA/LENR, Gif/Yvette CEDEX, France
General motivation
Experiment at the Fragment Separator
Inverse kinematics:
Fundamental questions:
how does the nuclear matter „look like“?, how does it behave ? ...
Astrophysical interest:
From ToF:
 /∆ ≈ 400
evolution of the early universe
supernovae explosions
formation and stability of neutron stars
A/∆A ≈ 400
(36m)
influenced by properties of the NM under extreme conditions (high T, P, ρ)
Once mass and charge are identified (A, Z are integer numbers) the velocity is calculated from B => very precise determination!
Properties of the NM:
 /∆ = B/∆B ≈ 2000
static – (in)compressibility, phase transitions, excitation…
dynamic – viscosity, momentum dependence of the mean field …
+ unambiguous identification and precise longitudinal momenta
+ full acceptance of most of the fragments
Present knowledge
Recent analysis:
(Danielewicz et al.)
- Only one fragment in one reaction measured, no correlations, no multiplicity
- Low acceptance for light and fission fragments (~10%)
Possible values of the nuclear incompressibility constrained by the experiments.
Velocity distributions of fragmentation residues
1 AGeV
238U+Ti @ 1 AGeV
T.Enqvist et al. NPA658(1999)47
M.V.Ricciardi et al. PRL 90(2003)212302
Science 298 (2002) 1592
Only the most extreme models of EoS could be excluded by the experiment
Basic characteristics:
Fact: Static properties are studied in dynamical processes !!!
width
position
shape
the interpretation is influenced by competing phenomena
Problem: most of the experimental observables is not selective; !!! The results are very often ambiguous !!!
Information on reaction mechanism !!!
Tools to investigate the nuclear matter
What can we learn from the spectator response?
Theoretical calculations for 4 different EoS: (Shi, Danielewicz, Lacey)
Experiment: (Enqvist and Ricciardi et al.))
(Fission events excluded !!!)
BUU calculations : 124Sn +124Sn Tlab= 800 MeV/u b = 5 fm
L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001)
Standard tools:
elliptic flow, sideward flow, transverse momentum, kaon production, …
! New !
! New !
Spectator response:
the spectator is not a passive witness, but rather a victim of violent participants !
Spectator response selectively reflects the MD properties of the nuclear MF !!!
Precise velocity measurement of projectile fragments provides a novel access to investigate the MD of nuclear mean field
L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001)
M.V.Ricciardi et al. PRL 90(2003)212302
CHARMS
(Collaboration for High-Accuracy Experiments
on Nuclear Reaction Mechanisms with the FRS)