Projectile Fragmentation and Isotopic Scaling in a Transport Approach

We investigate projectile fragmentation using transport theory coupled with statistical decay codes for the excited primary fragments. We concentrate on isotope distributions and on an isoscaling analysis of isotope ratios to obtain information about the symmetry energy. The analysis is performed depending on the impact parameter since the thermodynamic properties of the primary fragments depend on it strongly. We compare reaction systems with different neutron and proton excess, Ar-38, Ca-40+Be-9 and Ca-48, Ca-40+Be-9 both at 140 AMeV, to investigate the range of validity of the isoscaling assumption. We find it is well-justified for isotopes which are mainly produced by the secondary decay. However, for isotopes with N or Z near the incident projectile for grazing impact parameters, the process is more direct and the distributions are not well-represented by statistical ensembles. In the range of validity, the extracted symmetry energies are generally reasonable.