Charge correlations and isotopic distributions of projectile fragmentation events in 124Xe+112Sn at E/A=50 MeV

Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of Xe-124 projectiles with Sn-112 nuclei at E/A=50 MeV is examined. Charge correlations reveal that symmetric breakups occur with significant probability. By selecting on the parallel velocity of the heaviest fragment we minimize the entrance channel dynamics. Calculations with the statistical decay code GEMINI failed to reproduce the experimental charge correlations for any suitable combination of excitation energy and spin considered. A statistical multifragmentation model (SMM) in which breakup of low-density nuclear matter is assumed was able to reproduce the observed charge correlations. The << N >>/Z and isotope distributions of fragments were compared to the results of the SMM calculations. Describing the << N >>/Z of heavy fragments (Z>6) within SMM suggests that a reduction of the symmetry energy parameter from gamma=25 to 14 MeV is necessary. We observe that the yield of neutron-rich isotopes of heavy fragments is particularly sensitive to the symmetry energy.