  Autocorrelation of two pions produced in heavy-ion collisions at intermediate
$p_T$ is calculated in the framework of the recombination model. The
differences of the pseudo-rapidities and azimuthal angles of the two pions are
related to the angle between two shower partons in a jet. It is shown how the
autocorrelation distribution reveals the properties of jet cone of the shower
partons created by high-$p_T$ partons in hard collisions.
