Coupled-reaction-channel study of the 12C(α,8Be) reaction and the 8Be + 8Be optical potential

Background: Given the established 2 alpha structure of Be-8, a realistic model of four interacting alpha clusters must be used to obtain a Be-8 + Be-8 interaction potential. Such a four-body problem poses a challenge for the determination of the Be-8 + Be-8 optical potential (OP) that is still unknown due to the lack of the elastic Be-8 + Be-8 scattering data. Purpose: To probe the complex Be-8 + Be-8 optical potential in the coupled-reaction-channel (CRC) study of the alpha transfer C-12(alpha,Be-8) reaction measured at E-alpha, = 65 MeV and to obtain the spectroscopic information on the alpha + Be-8 cluster configuration of C-12. Method: The three- and four-body continuum-discretized coupled-channel (CDCC) methods are used to calculate the elastic alpha + Be-8 and Be-8 + Be-8 scattering at the energy around 16 MeV/nucleon, with the breakup effect taken into account explicitly. Based on the elastic cross section predicted by the CDCC calculation, the local equivalent OP's for these systems are deduced for the CRC study of the 12C(a,8Be) reaction. Results: Using the CDCC-based OP's and alpha spectroscopic factors given by the cluster model calculation, a good CRC description of the alpha transfer data for both the Be-8 + Be-8 and Be-8 Be-8(2+)* exit channels is obtained without any adjustment of the (complex) potential strength. Conclusion: The alpha + Be-8 and Be-8 + Be-8 interaction potential can be described by the three- and four-body CDCC methods, respectively, starting from a realistic alpha + alpha interaction. The alpha transfer C-12(alpha, Be-8) reaction should be further investigated not only to probe of the 4 alpha interaction but also the cluster structure of C-12.