  The standard model of particle physics lies in an enormous number of string
vacua. In a nonperturbative formulation of string theory, various string vacua
can, in principle, be compared dynamically, and the probability distribution
over the vacuum space could be calculated. In this paper, we consider
situations where the IIB matrix model is compactified on a six-dimensional
torus with various gauge groups and various magnetic fluxes, find matrix
configurations that provide the standard model matter content, and estimate
semiclassically the probability of their appearance.
