Аннотация:We present the first direct determination of asymptotic normalization coefficients (ANCs) for the ground andfirst excited states of 7Be from 3He + 4He elastic scattering phase shifts. The analysis draws upon the classicdatasets of two older low-energy measurements, long considered difficult due to internal inconsistencies andthe absence of systematic uncertainties. Employing single-level R-matrix fits, the mapping between reducedwidths and ANCs, and Bayesian inference, we reconstruct posterior distributions and quantify uncertainties.A key innovation of this study is the application and validation of the extrapolation method developed by ourgroup, specifically designed to extract ANC values in cases where direct low-energy information is lacking.Benchmarking against the latest measurements [Paneru et al., Phys. Rev. C 109, 015802 (2024)], which reportedonly R-matrix fits with fixed ANCs, confirms the predictive power and robustness of our approach. Our findingsshow that ANCs deduced from older scattering measurements are systematically lower than those inferredfrom radiative capture, thereby confirming earlier indications of a discrepancy between the two methods. Thiswork demonstrates both the originality and reliability of the extrapolation method as a powerful tool for ANCdetermination in nuclear astrophysics.
