Treatment of the Coulomb interaction in momentum space calculations of proton elastic scattering.

It is now well established' that the nonlocality of the first order Kerman-McManus-Thaler (KMT) optical potential for nucleon-nucleus scattering must be treated accurately in order to reproduce experimental data for proton-nucleus elastic scattering at intermediate energies. It thus proves very convenient to perform the associated numerical calculations in momentum space. It has been shown clearly, in the recent calculations of Elster et al. , that intermediate energy calculations of nucleon-nucleus scattering are highly sensitive to the details of the theoretical input to the calculations, a sensitivity which reveals itself most often near interference minima in spin-dependent observables and at larger scattering angles. The effects of the inclusion of the Coulomb interaction are, however, manifest in the same angular regions. Thus, to be able to probe details of our description of the strong nucleon-nucleus interaction, by comparison with the now high precision experimental data, it is vital that the effects of the Coulomb interaction can be included accurately to as large a scattering angle as can reasonably be achieved. The common approach to incorporating the Coulomb potential in momentum space, and that adopted here, is to use, in the solution of the integral equation, a free particle Green's function and to add the mornenturn space representation of the Coulomb interaction to the Snite ranged (in configuration space) nuclear interactions Vz. This procedure is, however, complicated by the I/q singularity in the momentum space representation of the Coulomb interaction. Approximate prescriptions, to overcome this difFiculty, have been discussed in the literature and are examined here. We present an alternative approximate, simple and stable method which yields more accurate calculations of reaction observables.