  Multi-boson symmetrization effects on two-particle Bose-Einstein
interferometry are studied for ensembles with arbitrary multiplicity
distributions. In the general case one finds interesting residual correlations
which require a modified framework for extracting information on the source
geometry from two-particle correlation measurements. In sources with high
phase-space densities, multi-boson effects modify the Hanbury Brown-Twiss (HBT)
radius parameters and simultaneously generate strong residual correlations. We
clarify their effect on the correlation strength (intercept parameter) and thus
explain a variety of previously reported puzzling multi-boson symmetrization
phenomena. For event ensembles of (approximately) fixed multiplicity, the
residual correlations lead to a minimum in the correlation function at non-zero
relative momentum, which can be practically exploited to search, in a
model-independent way, for multi-boson symmetrization effects in high-energy
heavy-ion experiments.
