Final State Interactions in Near Threshold Meson Production from pp Collisions

We analyse the experimental data on near threshold $\pi$, $\eta$, $\omega$, $\eta'$ and $K^+$ production from $pp$ collisions and show that all information gained so far is compatible with approximately constant production matrix elements when including the rescattering between the baryons in the final states. Different methods to include the final state interactions are discussed and their range of validity is indicated. We, furthermore, show that Dalitz plots for the proton-meson invariant mass spectra at different energies should be suited to distinguish between final state interactions and resonant production amplitudes.