Investigation on possible cluster contribution to elastic scattering of protons by 12C at different en¬ergies

The elastic scattering of protons by12C has been analysed at energies from 3.0 to 61.4 MeV. The experimental data have been taken partly from the literature. The discrepancies between the predictions of the optical model and the experimental angular distributions are attributed to the presence of α-cluster structure in the target. We have evaluated, on the basis of a simple semi-classical model, a mean contribution of (19.5±2.0)% to the experimental elastic-scattering cross-section due to cluster structure. The mean distance between the alphas in12C, a free parameter in the model here proposed, has been evaluated under the hypothesis of symmetrical spatial configuration. Its mean value is (4.0±0.1) fm.