Proton total reaction cross sections of carbon from 16 to 28 MeV

Abstract

Optical model analysis of the elastic scattering of 18 to 31 MeV protons from carbon has shown that fairly wide variations in the optical model parameters are necessary to reproduce the data. A later analysis of these data in which it was assumed that the scattering amplitude is described by the sum of optical model and Breit-Wigner terms has indicated possible resonances at 19.8, 20.01, and 24.9 MeV (c.m.). The later analysis predicts an inflection point in the proton total reaction cross section at about 21 MeV (lab). In this work the reaction cross sections were measured in the energy range 16 to 28 MeV using the anti-coincidence beam attenuation technique, and the energy variation was achieved with beryllium absorbers and subsequent magnetic analysis. The measured reaction cross section agrees well with the cross section predicted by the later analysis except that there is a weak maximum instead of an inflection point at about 21 MeV (lab).