Coupled-channels treatment of $^7\mathrm{Be}(p,\gamma)^8\mathrm{B}$ in effective field theory

TL;DR

This paper uses halo effective field theory with coupled-channels to calculate E1 and M1 contributions to the $^7$Be(p,γ)$^8$B reaction at low energies, including the excited core state, and compares results with previous models.

Contribution

It introduces a coupled-channels approach with explicit excited core states in halo EFT and provides a revised analysis differing from prior calculations.

Findings

Calculated $S_{17}(0)=21.0(7)$ eV b using Bayesian inference.

Included M1 transition near the $1^+$ resonance, improving reaction modeling.

Disagreed with previous EFT calculations in formalism and analysis.

Abstract

The E1 and M1 contributions to $^7\mathrm{Be}(p,\gamma)^8\mathrm{B}$ at low energies are calculated in halo effective field theory. The excited $^7\mathrm{Be}^\star$ core is included as an explicit degree of freedom in a coupled-channels calculation. The E1 transition is calculated up to next-to-next-to-leading order. The leading contribution from M1 transition that gives significant contribution in a narrow energy region around the $1^+$ resonance state of $^8$B is included. We compare our results with previous halo effective field theory calculations that also included the $^7\mathrm{Be}^\star$ as an explicit degree of freedom. We disagree with these previous calculations in both the formal expressions and also in the analysis. Bayesian inference of the data gives $S_{17}(0)=21.0(7)$ eV b when combined with the expected theory error.