Binding Energy of Muonic Beryllium: Perturbative versus All--Order Calculations

TL;DR

This paper compares perturbative and all-order methods for calculating the ground-state binding energy of muonic beryllium, demonstrating their agreement and providing a tool for precise charge radius extraction and theoretical unification.

Contribution

It introduces a comprehensive approach that bridges calculations for light and heavy muonic systems, enhancing theoretical predictions across all charge numbers.

Findings

Both methods agree within one part-per-million of total energy.

Provides a parametrization for extracting the $^9$Be charge radius.

Demonstrates the feasibility of a unified relativistic approach.

Abstract

We compute the ground-state binding energy of muonic $^9$Be in two ways: first, the fully perturbative treatment of the nuclear-size effect often employed in light systems, and second, an approach that accounts for the finite-nuclear-size to all orders (and is inspired by calculations otherwise employed for heavy muonic ions). The results are compared term by term and show that both approaches agree to better than one part-per-million of the total energy. The objective of this work is twofold. The first is practical: to provide a parametrization that allows the extraction of the $^9$Be charge radius from recent and forthcoming experiments with high precision. The second is more conceptual: to act as a bridge between the community working on calculations for light systems and those focusing on heavy systems, demonstrating that the fully relativistic approach otherwise chosen for heavy systems can be enhanced to cover theoretical predictions for all charge numbers.