  A simple model, based on two parallel and independent N N -> d pi processes,
has recently been proposed for two-pion production in the d d -> alpha X
reaction. It reproduces all observed features, including the sharp peak
structure in momentum distributions (the ABC effect) and the strong
oscillations in the deuteron vector and tensor analyzing powers. This model is
now extended to describe also four-pion production with the same basic
mechanism, but with two n p -> d pi pi processes as input. The calculations of
the high missing mass spectra are within about 30% of the experimental data for
beam energies in the range 1.9 < T_d < 2.4 GeV.
