The momentum spectrum of He-4 particles from d + d reactions at E-lab
= 569 MeV has been measured at zero degrees in the laboratory. The mis
sing-mass spectrum is consistent with a pure phase space behaviour for
the isospin zero channel of two pions, corresponding to a total cross
section of 43 +/- 5 nb. (C) 1997 Elsevier Science B.V.