Correlations of projectile like fragments in heavy ion reactions at Fermi energy

TL;DR

This study investigates correlations between projectile-like fragments emitted in heavy ion reactions at Fermi energy, revealing significant differences based on emission angles and supporting an inelastic breakup model involving complex fragment trajectories.

Contribution

It provides new experimental data on fragment correlations and interprets them with a semi-classical model, highlighting inelastic breakup mechanisms at Fermi energies.

Findings

Large difference in correlations depending on emission angles.

Evidence supporting inelastic breakup process.

Charge correlation trends consistent with complex fragment trajectories.

Abstract

Correlations between pairs of projectile-like fragments, emitted by the system ${^{16}O}+{^{197}Au}$ at the laboratory bombarding energy of 515 MeV, have been studied under two stipulated conditions: (1) at least one member of the pair is emitted at an angle less than the grazing angle for the system, (2) both the members of the pair are emitted at angles larger than the grazing angle. A surprisingly large difference, by more than an order of magnitude, is found between the correlations for the two cases. This observation could be explained on the basis of a simple semi-classical break up model. Further analysis of the variation of the charge correlation function with the difference in the nuclear charges of the correlated pair showed trends which are consistent with an "inelastic break up process", in which the projectile breaks up at the radius of contact, in such a way that, one fragment (preferably the lighter) is emitted to one side within the grazing angle, while the other orbits around the target nucleus for a while and emerges on the other side, at a negative scattering angle, much like in a deep inelastic scattering.