Refuting The Nature Of The Sixth 0+ Hoyle-analogue State Candidate In 16O

A prominent candidate for a Hoyle-analogue state in $\mathrm{^{16}O}$ is the $0_{6}^{+}$ state, previously observed at $E_{x} = 15.097(5)$ MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-$\alpha$ cluster state, analogous to the Hoyle state in $\mathrm{^{12}C}$. Whilst much theoretical work has been performed to reconcile a calculated $\alpha$-cluster state with this resonance, the experimental information on this state remained very scarce. To investigate this state, the $\mathrm{^{16}O}(\alpha, \alpha^{\prime})$ reaction was studied at $\theta_{lab}=0^{\circ}$ at an incident energy of $\textrm{E}_{lab}$ = 200 MeV using the K600 magnetic spectrometer at iThemba LABS. For the first time, the decay channels of the $E_{x} = 15.097(5)$ MeV state were isolated using a large acceptance silicon-strip detector array at backward angles. The lineshapes of the states were analysed within a phenomenological R-matrix framework. Results indicate the presence of a resonance at $E_{x} \approx 15$ MeV which does not exhibit a $J^{\pi} = 0^{+}$ nature.