# Core-excitation effects in ${}^{20}\mathrm{O}(d,p){}^{21}\mathrm{O}$ transfer reactions: Suppression or enhancement?

## TL;DR

This study uses advanced calculations to analyze how core excitation influences transfer reactions in oxygen isotopes, revealing that effects vary with energy and angular momentum transfer, affecting cross sections and angular distributions.

## Contribution

It introduces a detailed Faddeev-type calculation including core excitation effects, showing their complex impact on transfer reactions beyond simple spectroscopic factor adjustments.

## Key findings

- Core excitation effects can suppress or enhance cross sections depending on angular momentum transfer.
- At higher energies, core-excitation effects become more complex and cannot be simply related to spectroscopic factors.
- The effects result from a complex interplay between two- and three-body contributions.

## Abstract

${}^{20}\mathrm{O}(d,p){}^{21}\mathrm{O}$ transfer reactions are described using momentum-space Faddeev-type equations for transition operators and including the vibrational excitation of the ${}^{20}\mathrm{O}$ core. The available experimental cross section data at 10.5 MeV/nucleon beam energy for the ${}^{21}\mathrm{O}$ ground state $\frac52^+$ and excited state $\frac12^+$ are quite well reproduced by our calculations including the core excitation. Its effect can be roughly simulated reducing the single-particle cross section by the corresponding spectroscopic factor. Consequently, the extraction of the spectroscopic factors taking the ratio of experimental data and single-particle cross section at this energy is a reasonable procedure. However, at higher energies core-excitation effects are much more complicated and have no simple relation to spectroscopic factors. We found that core-excitation effects are qualitatively very different for reactions with the orbital angular momentum transfer $\ell=0$ and $\ell=2$, suppressing the cross sections for the former and enhancing for the latter, and changes the shape of the angular distribution in both cases. Furthermore, the core-excitation effect is a result of a complicated interplay between its contributions of the two- and three-body nature.