Nuclear rainbow and the EOS of cold nuclear matter

Abstract

Elastic scattering of strongly-bound light nuclei at energies of 10–70 MeV/nucleon shows the phenomenon of “Rainbow scattering” which is associated with strongly attractive potentials and deflections into “negative” angles. This process involves a strong overlap of nuclear densities (up to twice the saturation density of nuclear matter), but rather weak absorption due to the high Q-values for excitations and high separation energies of nucleons. In particular, elastic 16O + 16O scattering has been studied with high precision, over a wide range of angles and energies. At high energies, a systematics of primary Airy minima has been established, while at lower energies higher-order Airy structures were identified. Elastic data at all energies are consistently described by the potentials obtained from a self-consistent folding model using a weakly density dependent nucleon-nucleon interaction. This same density dependent interaction gives, within the Hartree-Fock formalism, a soft equation of state (EOS) for cold nuclear matter (with the nuclear incompressibility K ≈ 230 MeV). We also show that the Pauli-blocking, expected at large density overlap, is strongly reduced if the mean field contribution to the relative momenta of nucleons in the dinuclear system is treated self-consistently. Similar study of other refractive systems also confirms the soft EOS for cold nuclear matter.