FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

Isospin-dependent multifragmentation of relativistic projectiles
Collaborators: N. Buyukcizmeci 1 , A.S. Botvina, I.N. Mishustin, W. Trautmann 2 et al.
1 Selcuk University, Konya, Turkey 2 GSI, Darmstadt
Multifragmentation is an universal phenomenon occurring when a large amount of energy is deposited in a
nucleus. It is challenging to describe the production of fragments in multifragmentation simultaneously with
evaporation and fission which have been already studied extensively. It is also important that the physical conditions
in some stellar processes (e.g., during collapses of massive stars associated with supernova explosions)
is essentially determined by the state of hot nuclear matter at subnuclear density which can be investigated in
multifragmentation reactions. There is a considerable interest to how the nuclear processes are modified with
the neutron richness of matter. For this reason the ALADIN collaboration at GSI has performed experimental
studies of fragmentation of relativistic projectiles with different mass and isospin content ( 107 Sn, 124 Sn, and
124 La), at beam energy of 600 MeV per nucleon.
In this work we have applied a well known statistical multifragmentation model (SMM) for simulation of
the projectile break-up, and extraction of new information on properties of nuclear matter at various isospin
asymmetries. We were able to reproduce simultaneously the charge yields of fragments, their mass (isotope)
distributions, and correlations of these observables with excitation energy. For example, in Fig. 1 we show
the quality of description of fragment charge distributions at different excitation energies (controlled by the
charge bound in fragments) produced at disintegration of the 124 Sn projectile. We have demonstrated that inmedium
reduction of the nuclear symmetry energy is necessary for successful description of the whole set of
the data. Besides improving nuclear reaction models, this conclusion has consequences for many astrophysical
processes, since the symmetry energy influences nuclear composition and weak reactions in stellar matter.
Figure 1: Experimental cross sections dσ/dZ for the
fragment production following collisions of 124 Sn projectiles
sorted into five intervals of Zbound/Z0 with centers
as indicated and width 0.2 (symbols) in comparison
with normalized SMM calculations (lines). Different
scale factors were used for displaying the cross sections
as indicated.
Related publication in 2011:
1) R. Ogul, A.S. Botvina, U. Atav, N. Buyukcizmeci, I.N. Mishustin, W. Trautmann et al., Isospin dependent
multifragmentation of relativistic projectiles, Phys. Rev. C83, 024608 (2011).
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