Differential cross sections of the reactions pp→dπ+ and pp→pnπ+ have been measured at Tp=400 MeV by detecting the charged
ejectiles in the angular range 40≤ΘLab≤21∘. The
deduced total cross sections agree well with those published previously for
neighbouring energies. The invariant mass spectra are observed to be strongly
affected by Δ production and NN final-state interaction. The data are
well described by Monte Carlo simulations including both these effects. The
ratio of pp→pnπ+ and pp→dπ+ cross sections also compares
favourably to a recent theoretical prediction which suggests a dominance of
np-production in the relative 3S1-state.Comment: 17 pages, 5 figure