Description of Four-Body Breakup Reaction with the Method of Continuum-Discretized Coupled-Channels

We present a method of smoothing discrete breakup S-matrix elements calculated by the method of continuum-discretized coupled-channels (CDCC). This smoothing method makes it possible to apply CDCC to four-body breakup reactions. The reliability of the smoothing method is confirmed for two cases, Ni-58(d, pn) at 80 MeV and the El transition of He-6. We apply CDCC with the smoothing method to a He-6 breakup reaction at 22.5 MeV. Multistep breakup processes are found to be important.