Femtoscopy with unlike particles

The possibilities of unlike particle correlations for a study of space--time characteristics of particle production are demonstrated. The correlation data from heavy ion collisions is discussed, particularly - in terms of the transport RQMD and hydrodynamic models. An attention is paid to the relative space-time asymmetries in the production of different particle species, measured as a ratio of the correlation functions corresponding to different directional selections of the relative momentum vector. Being sensitive to the relative time delays and to the intensity of collective flows, these asymmetries can become a promising tool in a study of the deconfinement transition and the formation of quark-gluon plasma.