Electromagnetic dissociation of relativisticO18nuclei

Measurements of fragment-production cross sections have been made with ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ projectiles of 1.7 GeV/nucleon incident upon targets of Be, C, Al, Ti, Cu, Sn, W, Pb, and U. We have found that the enhancement with high-$Z$ targets of cross sections for certain fragments agrees both in magnitude and $Z_T$ dependence with the predictions of the electromagnetic-dissociation process, which are based upon the known photonuclear cross sections and classical relativistic virtual-photon theory. We have found as well that factorization of the cross sections for nuclear processes is valid to an accuracy of better than 4%.