Novel Source of Nonlocality in the Optical Model

TL;DR

This paper introduces a novel nonlocality source in the optical model by adding a velocity-dependent term to fit neutron-12C scattering data, revealing new insights into nonlocal effects and improving fit quality.

Contribution

It presents a new form of nonlocality in the optical model using a velocity-dependent term, with fewer parameters and consistent energy variation, contrasting previous nonlocality models.

Findings

Successful fits to scattering angular distributions and analyzing power data

Fewer parameters than traditional local optical potentials

Nonlocality form differs from previous models

Abstract

In this work we fit $neutron$ - $^{12}C$ elastic scattering angular distributions in the energy range 12 to 20 MeV, by adding a velocity dependent term to the optical potential. This term introduces a wave function gradient, whose coefficient is real and position dependent, and which represents a nonlocality. We pay special attention to the prominent backscattering minima which depend sensitively on the incident energies, and which are a tell-tale of nonlocalities. Reasonable fits to the analyzing power data are also obtained as a by-product. All our potentials have the form of conventional Woods - Saxon shapes or their derivatives. The number of our parameters (12) is smaller than the number for other local optical potentials, and they vary monotically with energy, while the strengths of the real and imaginary parts of the central potential are nearly constants. Our nonlocality is in contrast to other forms of nonlocalities introduced previously.