FINAL-STATE INTERACTIONS IN 2-PARTICLE INTERFEROMETRY

We reconsider the influence of two-particle final state interactions ( FSI) on two-particle Bose-Einstein interferometry. We concentrate in p articular on the problem of particle emission at different times. Assu ming chaoticity of the source. we derive a new general expression for the symmetrized two-particle cross section. We discuss the approximati ons needed to derive from the general result the Koonin-Pratt formula. Introducing a less stringent version of the so-called smoothness appr oximation we also derive a more accurate formula. It can be implemente d into classical event generators and allows us to calculate FSI corre cted two-particle correlation functions via modified Bose-Einstein ''w eights.''