  A microscopic treatment of cumulative phenomena based on perturbative QCD
calculations of the corresponding quark diagrams near the threshold is
presented. To sum all diagrams like these the special technique based on the
recurrence relations was developed. The x-behaviour of the nuclear structure
function $F_{2}(x)$ in the cumulative region x>1 was found to be roughly
exponential, governed by an effective coupling constant, which depends on the
QCD coupling constant and quark mass. Two mechanisms for cumulative particle
production, direct and spectator ones, were analysed. It was shown that due to
final state interactions the leading terms of the direct mechanism contribution
are cancelled and the spectator mechanism is the dominant one. It leads to a
smaller slope of the particle production rates compared to the slope of the
nuclear structure function in the cumulative region, in agreement with the
recent experimental data. The slope difference is due to additional multiple
interactions between nuclear and projectile partons which enter the spectator
mechanism for the cumulative production. The different versions of
hadronization mechanisms of the produced cumulative quarks into hadrons are
also discussed.
