Observation of color-transparency in diffractive dissociation of pions

production in deep inelastic muon scattering [14], and in the energy andflavor dependences of vector meson production in epscattering at HERA [15]. In this paper,we report a direct observation of color transparency in the A-dependence of diffractive di-jetproduction by pions.The pion wave function can be expanded in terms of Fock states:Ψ = α|qq¯i+β|qqg¯ i+γ|q¯qgg i+··· . (1)The first (valence) component is dominant at large Q