# Finite-Size Effects in Heavy Halo Nuclei from Effective Field Theory

## TL;DR

This paper explores how finite-size effects influence the charge radii of heavy halo nuclei within Effective Field Theory, highlighting the importance of core size and proposing an organizational scheme for these effects.

## Contribution

It introduces a new organizational scheme in Halo EFT that accounts for finite-size effects in heavy cores, improving predictions of charge radii.

## Key findings

- Finite-size effects decrease as 1/A_c for heavy cores.
- Short-range operators can dominate the charge radius in one-neutron P-wave halos.
- Halo EFT remains highly predictive for one-proton halos.

## Abstract

Halo/Cluster Effective Field Theory describes halo/cluster nuclei in an expansion in the small ratio of the size of the core(s) to the size of the system. Even in the point-particle limit, neutron halo nuclei have a finite charge radius, because their center of mass does not coincide with their center of charge. This point-particle contribution decreases as $1/A_c$, where $A_c$ is the mass number of the core, and diminishes in importance compared to other effects, e.g., the size of the core to which the neutrons are bound. Here we propose that for heavy cores the EFT expansion should account for the small factors of $1/A_c$. As a specific example, we discuss the implications of this organizational scheme for the inclusion of finite-size effects in expressions for the charge radii of halo nuclei. We show in particular that a short-range operator could be the dominant effect in the charge radius of one-neutron halos bound by a P-wave interaction. The point-particle contribution remains the leading piece of the charge radius for one-proton halos, and so Halo EFT has more predictive power in that case.