SWANLOP: Scattering waves off nonlocal optical potentials in the presence of Coulomb interactions

Abstract

We introduce the package SWANLOP to calculate scattering waves and corresponding observables for nucleon elastic collisions off spin-zero nuclei. The code is capable of handling local and nonlocal optical potentials superposed to long-range Coulomb interaction. Solutions to the implied Schrödinger integro-differential equation are obtained by solving an integral equation of Lippmann–Schwinger type for the scattering wavefunctions, ψ=ϕC+GCUSψ, providing and exact treatment to the Coulomb force Arellano and Blanchon (2019). The package has been developed to handle potentials either in momentum or coordinate representations, providing flexible options under each of them. The code is fully self-contained, being dimensioned to handle any A≥4 target for nucleon beam energies of up to 1.1 GeV. Accuracy and benchmark applications are presented and discussed. Program summaryProgram title: SWANLOPCPC Library link to program files:https://doi.org/10.17632/89gw9jdfv4.1Licensing provisions: GNU General Public License, Version 2Programming language: FORTRAN-90Nature of problem: Optical model potentials constitute a valuable tool to investigate the physics involved in nuclear collisions and reactions with nucleonic probes. As such, it becomes essential to obtain accurate results for its associated scattering observables and corresponding scattering waves. An important feature of optical potentials is their nonlocal nature, arising from the fermionic nature of the (A+1)–nucleon problem together with the fact that effective nucleon–nucleon (NN) interactions are nonlocal as well. The superposition of Coulomb interaction to these nonlocal potentials poses non-trivial difficulties to obtain scattering waves and observables in collision processes.Solution method: The code performs the calculation of scattering waves associated to nonlocal potentials in the presence of the long-range Coulomb interactions, solving a Lippmann–Schwinger type integral equation for the scattering wavefunction. The potential can be given either in coordinate or momentum space. Phase-shifts and associated elastic scattering observables are extracted from the asymptotic behavior of the solution.