The $^{8}$Be nucleus and the Hoyle state in dissociation of relativistic nuclei

TL;DR

This paper reports on the study of relativistic nuclear dissociation using nuclear emulsion techniques, identifying specific unstable states like $^8$Be and the Hoyle state, with implications for nuclear clustering and astrophysics.

Contribution

It presents new experimental results on unstable nuclear states in relativistic dissociation, utilizing automated microscopy and complete fragment detection.

Findings

Identification of decays of $^8$Be, $^9$B, and the Hoyle state in nuclear dissociation.

Increased contribution of $^8$Be, $^9$B, and $^{12}$C(0$^+_2$) with higher alpha-particle multiplicity.

Demonstration of nuclear emulsion method's effectiveness with automated microscopy at JINR.

Abstract

The possibility of recording fragmentation events of relativistic nuclei in a nuclear emulsion, discovered back in the pioneering era of cosmic ray physics, opens up the prospect of using this method to study extremely cold ensembles of H and He nuclei in the interests of developing the physics of nuclear clustering and, possibly, expanding the scenarios of nuclear astrophysics. The results of the BECQUEREL experiment at JINR, obtained on unstable states in the relativistic dissociation of nuclei in a nuclear emulsion providing complete detection of fragments with record resolution are presented. According to the invariant masses calculated from the emission angles in the fragmentation cone, the decays of $^8$Be(0$^+$), $^8$Be(2$^+$), $^9$Be(1.7), $^9$B, $^6$Be, $^{12}$C(0$^+_2$) or the Hoyle state and $^{12}$C(3$^-$) have been identified. The contribution of $^8$Be(0$^+$), $^9$B and $^{12}$C(0$^+_2$) increases rapidly with the $\alpha$-particle multiplicity. Their structure and the diversity of parent nuclei suggest the fusion of the latter. The usage of automated microscopy for an analysis of exposures at the JINR NICA accelerator complex becomes a modern basis to apply the nuclear emulsion method.