Evidence against the Efimov effect in ¹²C from spectroscopy and astrophysics

The Efimov effect is a universal phenomenon in physics whereby three-body systems are stabilized via the interaction of unbound two-body sub-systems. A hypothetical state in ¹²C at 7.458 MeV excitation energy, comprising of a loose structure of three α-particles in mutual two-body resonances, has been suggested to correspond to an Efimov state in nuclear physics. Using the combined data sets from two recent experiments, one with the TexAT TPC to measure α-decay and the other with Gammasphere to measure γ-decay of states in ¹²C populated by ¹²N and ¹²B β-decay respectively, we achieve high sensitivity to states in close-proximity to the α-threshold in ¹²C. In parallel, calculations of the triple-alpha reaction rate show the inclusion of the Efimov state corresponds to a large increase in the reaction rate around 5×10⁷ K. This talk will summarize these results and demonstrate the remarkable sensitivity achieved in this combined approach.