Searching for states analogous to the 12C Hoyle state in heavier nuclei using the thick target inverse kinematics technique

TL;DR

This study uses the Thick Target Inverse Kinematics technique to search for alpha cluster states in heavier nuclei similar to the 12C Hoyle state, providing experimental evidence for potential analog states in 16O and 24Mg.

Contribution

First experimental application of TTIK to identify potential Hoyle-like states in heavier alpha-conjugate nuclei such as 16O and 24Mg.

Findings

Identified a structure at 15.2 MeV in 16O suggestive of a Hoyle-like state.

Re-analyzed data confirms a possible analogous state in 24Mg at around 34 MeV.

Demonstrated TTIK's effectiveness in studying multi-alpha decay channels.

Abstract

Identification of alpha cluster states analogous to the 12C Hoyle state in heavier alpha- conjugate nuclei can provide tests of the existence of alpha condensates in nuclei. Such states are predicted for 16O, 20Ne, 24Mg, 28Si etc. at excitation energies slightly above the multi-alpha particle decay threshold, but have not yet been experimentally identified. The Thick Target Inverse Kinematics (TTIK) technique can be used to study the breakup of excited self-conjugate nuclei into many alpha particles. The reaction 20Ne+{\alpha} was studied using a 20Ne beam at 12 MeV/nucleon from the K150 cyclotron at Texas A&M University. The TTIK method was used to study both single {\alpha}-particle emission and multiple {\alpha}-particle decays. Events with alpha multiplicity up to four were analyzed. The analysis of the three {\alpha} - particle emission data allowed the identification of the Hoyle state and other 12C excited states decaying into three alpha particles. The results are shown and compared with other data available in the literature. Although the statistics for events with alpha multiplicity four is low, the data show a structure at about 15.2 MeV that could indicate the existence in 16O of a state analogous to the 12C Hoyle state. This structure is confirmed by the re-analysis of alpha multiplicity four events from a previous experiment performed at 9.7 MeV/nucleon with a similar setup but lower granularity. Moreover, the reconstructed excitation energy of 24Mg for these events peaks at around 34 MeV, very close to the predicted excitation energy for an excited state analogous to the 12C Hoyle state in 24Mg.