  The role of the short-range part (repulsive core) of the proton-neutron
($pn$) potential in deuteron elastic breakup processes is investigated. A
simplified one-range Gaussian potential and the Argonne V4' (AV4') central
potential are adopted in the continuum-discretized coupled-channels (CDCC)
method. The deuteron breakup cross sections calculated with these two
potentials are compared. The repulsive core is found not to affect the deuteron
breakup cross sections at energies from 40 MeV to 1 GeV. To understand this
result, an analysis of the peripherality of the elastic breakup processes
concerning the $p$-$n$ relative coordinate is performed. It is found that for
the breakup processes populating the $pn$ continua with orbital angular
momentum $\ell$ different from 0, the reaction process is peripheral, whereas
it is not for the breakup to the $\ell=0$ continua (the s-wave breakup). The
result of the peripherality analysis indicates that the whole spatial region of
deuteron contributes to the s-wave breakup.
