1. Idea
BUU calculations : 124Sn +124Sn Tlab= 800 MeV/u b = 5 fm
L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001)
Observation
T.Enqvist et al. NPA658(1999)47
WCI3 Texas 2005

2. Experiment at the Fragment Separator
Inverse kinematics:
From ToF:
 /∆ ≈ 400
(36m)
A/∆A ≈ 400
Once mass and charge are identified (A, Z are integer numbers) the velocity is calculated from B => very precise determination!
 /∆ = B/∆B ≈ 2000
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3. Characteristics of the data
unambiguous identification & precise longitudinal momenta
limited acceptance: ±15mrad, ±1.5% in momentum
only one fragment in one reaction measured
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4. Information with limited acceptance (op.I)
single, predominantly largest residue per reaction unambiguously identified
mid-peripheral collisions investigated
the largest fragment is correlated with impact parameter
238U+Cu 1AGeV - ALADIN
fission
fission excluded
WCI3 Texas 2005

5. Information with limited acceptance (op.II)
Reconstruction of the velocity distribution:
limited momentum acceptance:
Several magnetic field settings need to be combined to get complete velocity distribution
136Xe+Pb at 1A GeV
21Ne
D. Henzlova PhD thesis (in preparation)
WCI3 Texas 2005

6. Information with limited acceptance (op.III)
How to distinguish fragmentation and fission?
238U (1 A GeV) + Pb
Fragmentation: heaviest residues fully accepted (A>90)
Fission: Only forward and backward component accepted
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7. Velocity correction for limited acceptance
Influence of limited angular acceptance on mean residue velocities is negligible (A ≥ 60) or small and correctable (25 ≤ A ≤ 60)
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