  Angular correlations measured in \pp and heavy ion collisions at the
Relativistic Heavy Ion Collider (RHIC) include a same-side (SS) 2D peak. In
peripheral \aa and p-p collisions the SS peak properties are consistent with
predicted minimum-bias jet correlations. However, in more-central \auau
collisions the SS peak becomes elongated on pseudorapidity $\eta$. Arguments
have been proposed to explain the SS peak $\eta$ elongation in terms of
possibly-fluctuating initial-state geometry multipoles coupled with radial flow
to produce final-state momentum-space multipoles. Such arguments are based on
Fourier decomposition of 2D angular correlations projected onto 1D azimuth. In
this analysis we show that measured correlation structure on $\eta$ (large
curvatures) establishes a clear distinction between the SS 2D (jet) peak and 1D
multipoles. Measured 2D peak systematics can predict inferred 1D Fourier
amplitudes interpreted as "higher harmonic flows." But 1D Fourier amplitudes
alone cannot describe 2D angular correlations. The SS 2D peak remains a unique
structure which can be interpreted in terms of parton scattering and
fragmentation in all cases.
