1. Isotopic composition of the residues produced in the fragmentation of 124Xe and 136Xe projectiles
Daniela Henzlova
GSI-Darmstadt, Germany
NSCL-MSU, East Lansing, Michigan

2. relativistic heavy-ion collisions
Introduction
abrasion
projectile spectator
participants
target spectator
properties of nuclear system under conditions of extreme temperatures and densities
relevant for astrophysical scenarios
relativistic heavy-ion collisions
weak isospin diffusion

3. Introduction evaporation ->
dominant influence on the final isotopic composition
R.J.Charity, Phys. Rev. C 58 (1998), 1073
explore isotopic distributions from two systems with very different N/Z
sensitivity to the initial isotopic composition and the length of evaporation process
extraction of properties of hot system?

4. Fragment Separator (FRS) – a high-resolution magnetic spectrometer
inverse kinematics
in-flight identification
mass identification:
position in scintillators
124Xe, 1AGeVc Pb
dE in ionisation chamber
ToF
Z/ΔZ ~ 200
A/ΔA ~ 400
high resolving power:

5. <N>/Z in a broad nuclear charge range
136Xe
136Xe
124Xe
124Xe+Pb 1 A GeV
136Xe+Pb 1 A GeV Z N
<N>/Z investigated in the broad nuclear charge range
cold residues preserve memory on the initial N/Z over the whole nuclear charge range (high excitation energies)
residue corridor not reached

6. Comparison with ABRABLA – influence of the cluster emission
ABRABLA – abrasion+evaporation code
n, p, alpha emission -> too strong removal of memory on initial N/Z
implementation of cluster emission (d, t, 3He, IMF (Z>2))
memory on initial N/Z not completely removed
not sufficient to reproduce <N>/Z of experimental data

7. Excitation energy introduced in abrasion
ABRABLA (abrasion+ablation) calculation
136Xe+Pb 1A GeV
124Xe+Pb 1A GeV
excitation energy above 3 MeV/A introduced
break-up of highly excited system

8. Comparison with ABRABLA – influence of the thermal conditions at the freeze-out of the break-up
E*=aT2
evaporation
<N>/Z of residues from 124Xe less sensitive to length of evaporation cascade
only including the nuclear break-up allows to reproduce <N>/Z of the final residues Tf=5-6 MeV and 3-4 MeV for Z>20 136Xe and 124Xe, respectively
final <N>/Z reflects the thermal conditions at the freeze-out

9. Summary comparison with ABRABLA:
isotopic distributions in the broad Z range reveal sensitivity to the initial N/Z
comparison with ABRABLA:
emission of complex clusters restores memory on the initial N/Z, but not sufficient to reproduce data
break-up results in improved agreement with data
Tf ~ 5-6 MeV for 136Xe
Tf ~ 3-4 MeV for 124Xe
three stage reaction process needed
final <N>/Z reveal sensitivity to the length of an evaporation cascade following the nuclear break-up