  Multi-particle correlation observables in the Relativistic Heavy Ion Collider
small system scan are computed in a framework that contains both initial state
momentum anisotropies from the Color Glass Condensate effective theory and
final state hydrodynamic evolution. The initial state is computed using the
IP-Glasma model and coupled to viscous relativistic hydrodynamic simulations,
which are followed by microscopic hadronic transport. All parameters of the
calculation were previously constrained using experimental data on Au+Au
collisions at the same center of mass energy. We find that the qualitative
features of the experimental data, such as the system and centrality dependence
of the charged hadron momentum anisotropy, can only be reproduced when final
state interactions are present. On the other hand, we also demonstrate that the
details of the initial state are crucially important for the quantitative
description of observables in the studied small systems, as neglecting the
initial transverse flow profile or the initial shear stress tensor, which
contain information on the momentum anisotropy from the Color Glass Condensate,
has dramatic effects on the produced final state anisotropy. We further show
that the initial state momentum anisotropy is correlated with the observed
elliptic flow in all small systems, with the effect increasing with decreasing
multiplicity. We identify the precise measurement of $v_2$ in d+Au and Au+Au
collisions at RHIC energy at the same multiplicity as a means to reveal effects
of the initial state momentum anisotropy.
