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

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

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?

Fragment Separator (FRS) – a high-resolution magnetic spectrometer inverse kinematics in-flight identification mass identification: position in scintillators 124Xe, 136Xe @ 1AGeVc Pb dE in ionisation chamber ToF Z/ΔZ ~ 200 A/ΔA ~ 400 high resolving power:

<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

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

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

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

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