Effects of Nonlocality on Transfer Reactions

TL;DR

This paper investigates the effects of nonlocal interactions on transfer reactions in nuclear physics, demonstrating significant discrepancies when nonlocality is approximated or ignored, and emphasizing the need for exact nonlocality inclusion in reaction models.

Contribution

The study provides a comprehensive analysis of nonlocality effects in transfer reactions, comparing local and nonlocal models, and introduces methods to incorporate nonlocality consistently into reaction calculations.

Findings

Nonlocality affects wave functions in the nuclear interior and surface regions.

Discrepancies of 15-50% in transfer distributions when using local versus nonlocal potentials.

Including nonlocality exactly reduces discrepancies, highlighting the importance of accurate models.

Abstract

We solved the nonlocal scattering and bound state equations using the Perey-Buck type interaction, and compared to local equivalent calculations. Using the distorted wave Born approximation we construct the T-matrix for (p,d) transfer on 17O, 41Ca, 49Ca, 127Sn, 133Sn, and 209Pb at 20 and 50 MeV. Additionally we studied (p,d) reactions on 40Ca using the the nonlocal dispersive optical model. We have also included nonlocality consistently into the adiabatic distorted wave approximation and have investigated the effects of nonlocality on on (d,p) transfer reactions for deuterons impinged on 16O, 40Ca, 48Ca, 126Sn, 132Sn, 208Pb at 10, 20, and 50 MeV. We found that for bound states the Perry corrected wave functions resulting from the local equation agreed well with that from the nonlocal equation in the interior region, but discrepancies were found in the surface and peripheral regions. Overall, the Perey correction factor was adequate for scattering states, with the exception for a few partial waves. Nonlocality in the proton scattering state reduced the amplitude of the wave function in the nuclear interior. The same was seen for nonlocality in the deuteron scattering state, but the wave function was also shifted outward. In distorted wave Born approximation studies of (p,d) reactions using the Perey-Buck potential, we found that transfer distributions at the first peak differed by 15-35% as compared to the distribution resulting from local potentials. When using the dispersive optical model, this discrepancies grew to 30-50%. When nonlocality was included consistently within the adiabatic distorted wave approximation, the disagreement was found to be ~40%. This highlights the necessity to pursue reaction formalisms that include nonlocality exactly.