0 v 3 2 2 M ar 1 99 7 Probing the exchanged object ( s ) in diffractive scattering

The reaction mechanisms of the following proton diffractive scattering processes are studied and compared with one another: γ∗p → V p, γ∗p → Xp, pp → (ΛK+)p and pA → ΛK+A (Here, γ∗ stands for the space-like photon in inelastic electronproton scattering, V for the vector mesons ρ, ω, φ, J/ψ, and A for a target nucleus.) It is shown that, by taking parity, and C–parity conservation into account, the existing data for these reactions strongly suggest the following: A considerable part of the objects exchanged between projectile and target in the above-mentioned processes are virtual quark-antiquark pairs in color-singlet states with J = 0−+, I = 0+, where J stands for total angular momentum, I for isospin, P , C and G stand for parity, C-parity and G-parity respectively. Such quark-antiquark pairs are created by soft-gluon interactions. New experiments are suggested; and predictions for such experiments are made.