Three-body effects in the Hoyle-state decay

TL;DR

This paper models the decay of the Hoyle state into three alpha particles, revealing features of both sequential and direct decay processes and analyzing Coulomb effects on the decay spectrum.

Contribution

It introduces a sequential $R$-matrix model combined with a toy Coulomb interaction model to study Hoyle state decay mechanisms and phase-space distributions.

Findings

Sequential decay features resemble direct decay in phase-space distributions

Coulomb interactions significantly influence the decay spectrum

Predictions made for direct decay phase-space distributions and interference effects

Abstract

We use a sequential $R$-matrix model to describe the breakup of the Hoyle state into three $\alpha$ particles via the ground state of $^8\mathrm{Be}$. It is shown that even in a sequential picture, features resembling a direct breakup branch appear in the phase-space distribution of the $\alpha$ particles. We construct a toy model to describe the Coulomb interaction in the three-body final state and its effects on the decay spectrum are investigated. The framework is also used to predict the phase-space distribution of the $\alpha$ particles emitted in a direct breakup of the Hoyle state and the possibility of interference between a direct and sequential branch is discussed. Our numerical results are compared to the current upper limit on the direct decay branch determined in recent experiments.