LIFETIMES AND SIZES FROM 2-PARTICLE CORRELATION-FUNCTIONS

We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the t wo-particle correlation function for azimuthally symmetric expanding s ources. We derive model-independent expressions for the YKP fit parame ters and discuss their physical interpretation. We use them to evaluat e the YKP fit parameters and their momentum dependence for a simple mo del for the emission function and propose new strategies for extractin g the source lifetime. Longitudinal expansion of the source can be see n directly in the rapidity dependence of the Yano-Koonin velocity.