Search for rare 3-α decays in the region of the Hoyle state of 12C

Abstract

We performed a refined analysis of the data collected with the CHIMERA detector with the aim of searching rare 3-α decay modes near the Hoyle state of 12C. In particular we investigated the direct and sequential decay modes of the Hoyle state including also the recently suggested Efimov state. The comparison of selected events with simulations constrains the precision achievable with measurements in different experimental conditions. We observe good sensitivities to different decay scenarios also in the CHIMERA spherical region notwithstanding its limited angular resolution. The search for the decay of the Efimov state in 12C was performed by using new selection strategies as suggested by simulations. The obtained results are not conclusive, however, we are able to exclude the presence of a sequential decay of this state, while our data could be compatible with its direct decay.