New determination of the astrophysical SE1 factor of the C12(α,γ)</mml…

The ¹²C(α,γ)¹⁶O reaction substantially influences the abundance ratios of the main isotopes of carbon and oxygen and hence has been regarded as the holy grail in nuclear astrophysics. Its importance lies in the fact that it significantly affects the yield of key elements and that it plays a crucial role in the study of the mass gap of black holes. This reaction's cross section is greatly influenced by the subthreshold state 7.117-MeV 1^- of ¹⁶O, which is challenging to determine. To study such states the α-cluster transfer reaction can be helpful. In this work, the angular distribution of the ¹²C(¹¹B,⁷Li)¹⁶O reaction was measured, leading to the 7.117-MeV 1^- state at E_¹¹B(lab)=50 MeV. By using the finite-range distorted-wave Born approximation and coupled-reaction-channel analysis, we obtained the asymptotic normalization coefficient (ANC) to be (2.54±0.40)×10²⁸ fm^-1 and the reduced α width to be 4.92±0.77 keV at a channel radius of 6.5 fm. Then, by using the R-matrix code azure, we calculated the astrophysical S factor of the ¹²C(α,γ)¹⁶O reaction and found that the astrophysical SE1 (300) factor of the ground-state transitions is 55.3±9.0 keV b. This value is lower than what was found in previous works, indicating that the S factor is highly sensitive to the ANC.