  We present results for the three-cluster breakup in deuteron-deuteron
collisions at 130 and 270 MeV deuteron beam energy. The breakup amplitude is
calculated using the first term in the Neumann series expansion of the
corresponding exact four-nucleon equations. In analogy with nucleon-deuteron
breakup where an equivalent approximation is compared with exact calculations,
we expect this single-scattering approximation to provide a rough estimation of
three-body breakup observables in quasifree configurations. We predict the
nucleon-deuteron and deuteron-deuteron three-cluster breakup cross sections to
be of a comparable size and thereby question the reliability of the recent
experimental data [A. Ramazani-Moghaddam-Arani, Ph.D. thesis, University of
Groningen, 2009; A. Ramazani-Moghaddam-Arani et al., EPJ Web of Conferences 3,
04012 (2010)] that is smaller by about three orders of magnitude. We also show
that an equivalent single-scattering approximation provides a reasonable
description of deuteron-deuteron elastic scattering at forward scattering
angles.
