# Effect of the Constant Potential in the Bethe-Salpeter Equation for Proton-Neutron Elastic Scattering

## TL;DR

This paper investigates how constant potential terms derived from the Bethe-Salpeter equation influence spin observables in proton-neutron elastic scattering, especially at 90 degrees, by extending the nucleon-nucleon potential to include next-order contributions.

## Contribution

It introduces the effect of constant potential terms in the Bethe-Salpeter framework on scattering wave functions and spin observables at intermediate energies.

## Key findings

- Constant potential terms significantly affect spin observables at 90 degrees.
- Next order in the potential improves the accuracy of scattering wave functions.
- The approach enhances understanding of nucleon-nucleon interactions at intermediate energies.

## Abstract

Nucleon-nucleon potential is given in coordinate space starting from the Bethe-Salpeter equation appropriate to elastic scattering at the intermediate energy region. The next order in the potential is added to construct the scattering wave for ${}^3S_1$ state. The constant terms have an effect on the spin observables particularly at the center of mass angle $\theta=90^{\circ}$