Diffractive Dissociation of High Momentum Pions

The diffractive dissociation of 500 GeV/c $\pi^-$ into di-jets is described as a way to measure the momentum distribution of quarks in the pion. The measurements of the pion diffractive dissociation were carried out using data from Fermilab E791. Preliminary results show that the $|q\bar {q}>$ Asymptotic wave function which was developed using perturbative QCD methods describes the data well for $Q^2 \sim 10 ~{\rm (GeV/c)^2}$. At these values signals of color transparency are expected and, indeed, observed through the $A$-dependence of the yield of the diffractive di-jets.