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The TexAT (Texas Active Target) detector is a new active-target time projection chamber (TPC) that was built at the Cyclotron Institute Texas A&M University. The detector is designed to be of general use for nuclear structure and nuclear astrophysics experiments with rare isotope beams. TexAT combines a highly segmented Time Projection Chamber (TPC) with two layers of solid state detectors. It provides high efficiency and flexibility for experiments with low intensity exotic beams, allowing for the 3D track reconstruction of the incoming and outgoing particles involved in nuclear reactions and decays.

Background: The structure of the Hoyle state, a highly α-clustered state at 7.65 MeV in 12 C, has long been the subject of debate. Understanding if the system comprises of three weakly-interacting α-particles in the 0s orbital, known as an α-condensate state, is possible by studying the decay branches of the Hoyle state. Purpose: The direct decay of the Hoyle state into three α-particles, rather than through the 8 Be ground state, can be identified by studying the energy partition of the 3 α-particles arising from the decay. This paper provides details on the break-up mechanism of the Hoyle stating using a new experimental technique. Method: By using beta-delayed charged-particle spectroscopy of 12 N using the TexAT (Texas Active Target) TPC, a high-sensitivity measurement of the direct 3 α decay ratio can be performed without contributions from pileup events. Results: A Bayesian approach to understanding the contribution of the direct components via a likelihood function shows that the direct component is < 0.043% at the 95% confidence level (C.L.). This value is in agreement with several other studies and here we can demonstrate that a small non-sequential component with a decay fraction of about 10 −4 is most likely. Conclusion: The measurement of the non-sequential component of the Hoyle state decay is performed in an almost medium-free reaction for the first time. The derived upper-limit is in agreement with previous studies and demonstrates sensitivity to the absolute branching ratio. Further experimental studies would need to be combined with robust microscopic theoretical understanding of the decay dynamics to provide additional insight into the idea of the Hoyle state as an α-condensate.

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