We present a formulation of the correlation problem in the transverse
plane of high-energy nuclear collisions. The correlation variable is t
he azimuthal angle between two transverse momenta. We assume that the
effects of quark-hadron phase transition are manifested in the existen
ce of a coherence angle chi and a parameter epsilon characterizing the
irreducible correlation. We then derive the consequences on the obser
vable two-particle correlation function.