The cascading 3.21 MeV and 4.44 MeV electric quadrupole transitions have been observed from the Hoyle state at 7.65 MeV excitation energy in 12C, excited by the 12C(p,p′) reaction at 10.7 MeV proton energy. From the proton-γ-γ triple coincidence data, a value of Γrad/Γ=6.2(6)×10−4 was obtained for the radiative branching ratio. Using our results, together with ΓπE0/Γ from Eriksen et al., Phys. Rev. C 102, 024320 and the currently adopted Γπ(E0) values, the radiative width of the Hoyle state is determined as Γrad=5.1(6)×10−3 eV. This value is about 34% higher than the currently adopted value and will impact on models of stellar evolution and nucleosynthesis.
@article{arxiv.2009.10915,
title = {The radiative width of the Hoyle state from $\gamma$-ray spectroscopy},
author = {T. Kibédi and B. Alshahrani and A. E. Stuchbery and A. C. Larsen and A. Görgen and S. Siem and M. Guttormsen and F. Giacoppo and A. I. Morales and E. Sahin and G. M. Tveten and F. L. Bello Garrote and L. Crespo Campo and T. K. Eriksen and M. Klintefjord and S. Maharramova and H. -T. Nyhus and T. G. Tornyi and T. Renstrøm and W. Paulsen},
journal= {arXiv preprint arXiv:2009.10915},
year = {2020}
}