Speaker
Description
Recently we measured the gamma decay probability of 12C levels over the threshold for particle decay as the Hoyle and the 9.64 MeV levels [1] measuring for the first time the two gamma decay of such last level. We observe in our data a large gamma decay width, 3 times larger than the already larger than systematic result of Kibedi et al [2]. Investigating also on the 3-alpha decay channel of the state [3] we have noted that our data are compatible with the population and direct decay of an Efimov state at 7.458 MeV recently proposed [4]. Moreover, our data exclude the sequential decay of such state. The population of an Efimov state with 0.3% population probability with respect to the one of the Hoyle state could explain the large measured gamma decay probability observed in our data. However, astrophysical consequences of the presence of the Efimov state could be dramatic as recently outlined by Bishop et al [5], with the violation of the Suda limit [6] for the formation of red giant stars. We will show that the exclusion of the sequential decay mode of the Efimov state strongly reduces the astrophysical impact of such a state on the creation of 12C at stellar temperature in the range from 10^7 to 10^8 K.
[1] G.Cardella et al, Phys. Rev. C, 104 (2021) 064315.
[2] T.Kibedi et al, Phys. Rev. Lett., 125 (2020) 182701.
[3] G.Cardella et al, Nucl. Phys. A, 1020 (2022) 122395.
[4] S. Zhang et al, Phys. Rev. C, 99 (2019) 044605.
[5] J.Bishop et al, Phys. Rev. C, 103 (2021) L051303.
[6] T. Suda, R. Hirschi, and M. Y. Fujimoto, The Astr. Jour. 741, 61 (2011).
