  Identical two-particle interferometry provides a scenario where interference
and exchange effects manifest at once. We present a detailed calculation of the
detection patterns in the two-particle two-slit experiment by extending
Feynman's Gaussian slit approach to multi-mode states. We show the existence of
two regimes depending on the mode distributions. In one of them we find a novel
behavior for bosons, with detection patterns almost equal to those of
distinguishable particles although the overlapping is large. As a byproduct of
our analysis we conclude that the interaction at the diffraction grating is an
efficient method to increase the initial overlapping. We propose a scheme,
within the reach of present day technology, to experimentally verify our
results.
