Measurement of Light-Cone Wave Functions by Diffractive Dissociation

Diffractive dissociation of particles can be used to study their light-cone wave function. Results from Fermilab experiment E791 for diffractive dissociation of 500 GeV/c $\pi^-$ mesons into di-jets are presented. The results show that the $|q\bar {q}>$ light-cone asymptotic wave function describes the data well for $Q^2 \sim 10 ~{\rm (GeV/c)^2}$ or more. Evidence for color transparency comes from a measurement of the $A$-dependence of the yield of the diffractive di-jets. It is proposed to carry out similar studies for the light-cone wave function of the photon.