Speaker
Description
Indirect methods play an important role in constraining the astrophysical rates of nuclear reactions. This talk will review several recent indirect studies that provided almost model-independent constraints for the key rates.
Neutron-upscattering enhancement of the triple-alpha reaction responsible for the production of carbon, suggested in [1], was investigated by measuring a time-inverse process, 12C(n,n’)12C(Hoyle), using the Texas Active Target Time Projection Chamber [2]. The total cross section for inelastic neutron scattering in carbon was measured in a wide range of energies, and the detailed balance and R-matrix analysis was used to establish the 12C(Hoyle)(n,n’)12C reactions cross section at astrophysically relevant energies [3].
The radiative width of the Hoyle state has a direct impact on the triple-alpha reaction rate. Recent measurements by Kibedi [4] reported a radiative width significantly above the previously recommended value [5]. I will report the results of the new study performed at the Cyclotron Institute, Texas A&M University, which provides a definitive resolution to the controversy.
The α-cluster properties of the ground state of 16O (the alpha asymptotic normalization coefficient, ANC) influence the low energy extrapolation for the key 12C(α,γ)16O reaction rate [6]. The new measurements at Texas A&M University used 12C(20Ne,16O)16O alpha-transfer reaction at sub-Coulomb energy to provide nearly model-independent constraints to the respective ANC values.
[1] M. Beard, S.M. Austin, R. Cyburt, Phys. Rev. Lett., 119, 112701 (2017).
[2] E. Koshchiy, et al., Nucl. Inst. Meth. Phys. Res. A, 957, 163398 (2020).
[3] J. Bishop, et al., Nature Communications, 13, 2151 (2022).
[4] T. Kibedi, et al., Phys. Rev. Lett., 125, 182701 (2020).
[5] M. Freer and H. Fynbo, Prog. Part. Nucl. Phys., 78, 1 (2014).
[6] R.J. deBoer, et al., Rev. Mod. Phys., 89, 035007 (2017).
