Model Independent Measurements of α-ANCs for the ¹²C(α,γ)¹⁶O Reaction

The ¹²C(α,γ)¹⁶O reaction is often considered the “Holy Grail” of nuclear astrophysics. It determines the absolute abundance of ¹²C and ¹⁶O in our universe and plays a fundamental role in the late stages of stellar evolution. However, direct measurement of this reaction is not possible with current experimental methods. This is because the Gamow peak at 300 keV is far below the Coulomb barrier where the cross section is on the order of 10⁻¹⁷ b. Low-energy extrapolations from higher energy measurements have proven challenging for this reaction and thus the reaction rate is not known to the desired uncertainty of 10%. One way to reduce uncertainties related to low-energy extrapolations is an indirect technique that measures Asymptotic Normalization Coefficients (ANCs) of bound states extracted from sub-Coulomb α-transfer reactions. This approach provides a valuable tool for studying astrophysically important reaction rates since the results are nearly model independent. One of the remaining sources of uncertainty for extrapolation is the α-ANC of the ground state of ¹⁶O. The preliminary results of an experiment performed at the Texas A&M University Cyclotron Institute using the TexPPAC detector will be presented for the sub-Coulomb α-transfer reaction of ¹²C(²⁰Ne,¹⁶O)¹⁶O.