Photonuclear interaction of high energy muons and tau leptons

The general formalism for the two-component description of inelastic lepton-nucleon scattering in the diffractive region is proposed. The nonperturbative contribution to electromagnetic structure functions of a nucleon is described by a modified generalized vector dominance model containing special cutoff factors restricting the phase volume of the initial $q\overline{q}$ pairs of the virtual photon's fluctuations. The perturbative QCD contribution is described by the phenomenological model suggested (in nonunitarized form) by Forshaw, Kerley, and Shaw. The formulas needed for a numerical calculation of the photonuclear cross sections integrated over ${Q}^{2}$ are presented. It is argued that in the case of photonuclear cross sections at superhigh energies of leptons $(E\ensuremath{\gtrsim}{10}^{5}\mathrm{GeV}),$ integrated over ${Q}^{2},$ the following two-component scheme is good enough: the nonperturbative contribution is approximated by the old parametrization of Bezrukov and Bugaev, and the perturbative one is described by the model of Forshaw, Kerley, and Shaw with the parameters determined from DESY data. The corresponding results of numerical calculations for the perturbative part are given, for the cases of $\ensuremath{\mu}A$ and $\ensuremath{\tau}A$ scattering at superhigh energies.