Energy dependence of $\sigma^{DD} / \sigma_{\rm tot}$ in DIS and shadowing corrections

We gereralize the Kochegov-McLerran formula for the ratio $\sigma^{DD}/\sigma_{tot}$ in perturbative QCD, using Mueller-Glauber approach for shadowing corrections and AGK cutting rules. We investigate several phenomenological approaches with the goal of obtaining results consisent with experimental data. We fail to reproduce the observed weak energy dependence of the ratio, and conclude that the soft nonperturbative contribution present at short distances must also be included.