Speaker
Description
Carbon burning is a key step in the evolution of massive stars, Type 1a supernovae and superbursts in x-ray binary systems. Determining the $^{12}$C+$^{12}$C fusion cross section at relevant energies by extrapolation of direct measurements is challenging due to resonances at and below the Coulomb barrier. A study of the $^{24}$Mg($\alpha$,$\alpha$')$^{24}$Mg reaction has identified several 0$^{+}$ states in $^{24}$Mg, close to the $^{12}$C+$^{12}$C threshold, which predominantly decay by $^{20}$Ne(g.s)+$\alpha$. These states were not observed in $^{20}$Ne($\alpha$,$\alpha_0$)$^{20}$Ne resonance scattering suggesting that they may have a dominant $^{12}$C+$^{12}$C cluster structure. Given the very low angular momentum associated with sub-barrier fusion, these states may play a decisive role in $^{12}$C+$^{12}$C fusion in analogy to the Hoyle state in helium burning [1]. We present estimates of updated $^{12}$C+$^{12}$C fusion reaction rates based on these newly observed potential resonances.
[1] P. Adsley. M. Heine, D.G. Jenkins et al., Phys. Rev. Lett. (in press)
