|Authors:||A.S. Botvina, O.V. Lozhkin, and W. Trautmann|
Phys. Rev. C65(2002)044610
Preprint GSI-2002-07, February 2002
Isotopic effects observed in fragmentation reactions
induced by protons, deuterons, and α particles of incident
energies between 660 MeV and 15.3 GeV on
112Sn and 124Sn targets are discussed.
The exponential scaling of the yield ratios with the
third component of the fragment isospin
t3 = (N-Z)/2 is observed
in all reactions, with scaling parameters that depend on the
Breakup temperatures for these reactions are deduced from
double ratios of isotopic yields and tested for their relation
with the isoscaling parameters.
The quantum statistical (QSM) and the statistical multifragmentation (SMM) models are used for interpreting the results. The observed isoscaling can be understood as a consequence of a statistical origin of the emitted fragments in these reactions. The SMM analysis shows that the exponent describing the isoscaling behavior is proportional to the strength of the symmetry term of the fragment binding energy. Using this result, a symmetry-term coefficient γ ~ 22.5 MeV for fragments at breakup is deduced from the experimental data. This is close to the standard value and supports SMM assumptions for the breakup configuration. An alternative method of determining the symmetry-energy coefficient, by using isotope distribution widths, is also discussed.
PACS numbers: 25.70.Mn, 25.70.Pq, 24.10.Pa, 25.40.Sc
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