Observation of strong final-state effects in pi+ production in pp collisions at 400 MeV

Abstract

Differential cross sections of the reactions $pp\to d\ddot{I}{€}^{+}$ and $pp\to pn\ddot{I}{€}^{+}$ have been measured at $T_p=400$ MeV by detecting the charged ejectiles in the angular range $4^0\le \hat{I}{˜}_{Lab}\le 21^{\circ }$. 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 $\hat{I}”$ production and $NN$ final-state interaction. The data are well described by Monte Carlo simulations including both these effects. The ratio of $pp\to pn\ddot{I}{€}^{+}$ and $pp\to d\ddot{I}{€}^{+}$ cross sections also compares favourably to a recent theoretical prediction which suggests a dominance of $np$-production in the relative ${}^3{S}_1$-state.

17 pages, 5 figures