  Disordered systems are characterized by the existence of many sample-
dependent local energy minima, that cause a stepwise response when the system
is perturbed. In this article we use an approach based on elementary
probabilistic methods to compute the complete probability distribution of the
jumps (static avalanches) in the response of mean-field systems described by
replica symmetry breaking; we find a precise condition for having a power-law
behavior in the distribution of avalanches caused by small perturbations, and
we show that our predictions are in remarkable agreement both with previous
results and with what is found in simulations of three dimensional systems of
soft-spheres, either at jamming or at slightly higher densities.
