Measurement of theADependence ofJψPhotoproduction

$\frac{J}{\psi }$ photoproduction has been measured from beryllium and tantalum targets by observing the yield of single muons at a transverse momentum of 1.65 GeV/c with a bremsstrahlung beam of $E_0=20\mathrm{}$ GeV. The results have been interpreted in terms of a nuclearoptics model to yield the $\psi$-nucleon total cross section. The result is ${\sigma }_{\psi N}=3.5\mathrm{}\pm 0.8$ mb.