Dynamic polarization potential and dynamical nonlocality in nuclear potentials: Nucleon-nucleus potential

Background: Of the two sources of nonlocality in nucleon-nucleus and nucleus-nucleus interactions, knock-on exchange and dynamically generated, almost all papers referring to nonlocality mention only the first. Purpose: Our purpose is threefold: to demonstrate a method for including dynamical nonlocality, for which a simple prescription (like the Perey factor for exchange nonlocality) is unknown, within distorted wave Born approximation (DWBA) calculations; to identify signatures of dynamic nonlocality and illuminate the extent to which the presence of such nonlocality can influence the extraction of spectroscopic information from direct reactions, and more generally, to increase our understanding of nucleus-nucleus interactions. Methods: After reviewing existing indications of dynamically induced nonlocality, DWBA transfer calculations are presented which compare results involving dynamically nonlocal potentials with those involving their local equivalents. The dynamical nonlocal potentials are generated in situ by the presence of channel coupling and the local equivalents are generated by inversion of the corresponding coupled channel elastic S matrix. This method obviates the need for solving integro-differential equations for including nonlocal potentials in DWBA. Results: The coupling of nucleons to collective states of the target nucleus induces dynamical nonlocality in the nucleon-nucleus interaction that has a significant effect on (p,d) reactions at energies relevant to spectroscopic studies. Conclusions: A method for studying the contribution of dynamically induced nonlocality in nuclear interactions has been demonstrated. Dynamically induced nonlocality should not be overlooked in the analysis of direct reactions. The method can also be applied to dynamic nonlocality due to projectile excitation.