"nuclear matter" approach to the energy dependence of the real part of the proton-nucleus optical potential at intermediate incident energies
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We present and discuss here the results of a calculation of the real part of the potential energy of a proton within nuclear matter, making use of the realistic Reid soft-core nucleon-nucleon interaction, which we justify in the intermediate-energy range. The problem of evaluating the volume of the real part of the proton-nucleus optical-model potential as a function of incident energy is solved with the help of a number of techniques previously developed in the literature of nuclear-matter theory. We find good agreement with results of various phenomenological studies over an energy range of 100 to 1050 MeV incident proton energy for targets /sup 40/Ca and /sup 208/Pb, which we adopt as test cases. Furthermore, we consider a number of higher-order corrections to our initial result; all of these have minimal effect in the energy regime we have considered except for the third-order correction proposed by Rajaraman, as we demonstrate and discuss. Finally, we show that the conventional approach to the nucleon-nucleus potential at medium energy, the so-called Rayleigh-Lax potential, which makes use of a straightforward impulse approximation and an empirical nucleon-nucleon scattering amplitude, is in gross disagreement both with phenomenological findings concerning the energy dependence of the optical potentialmore » and with results of the present calculations. We make an effort to shed some light on the physical reasons for the failure of the Rayleigh-Lax approach, as opposed to the success of other approaches relying upon realistic nucleon-nucleon interactions or phase shifts rather than an empirical medium-energy nucleon-nucleon T matrix.« less