Boundary and expansion effects on two-pion correlation function in relativistic heavy-ion collisions

We examine the effects that a confining boundary together with hydrodynamical expansion play on two-pion distribution in relativistic heavy-ion collisions. We show that the effects arise from the introduction of further correlations due both to collective motion and the system's finite size. As is well know, the former leads to a reduction in the apparent source radius with increasing and large average pair momentum K. However, for small K, the presence of boundary leads to a decrease of the apparent source radius with decreasing K. These two competing effects produce a maximum at a finite value of the effective source radius as a function of K.