  Event geometry and initial state correlations have been invoked as possible
explanations of long range azimuthal correlations observed in high multiplicity
p+p and p+Pb collisions. We study the rapidity dependence of initial state
momentum correlations and event-by-event geometry in $\sqrt{s}=5.02~\rm{TeV}$
p+Pb collisions within the 3+1D IP-Glasma model~\cite{Schenke:2016ksl}, where
the longitudinal structure is governed by JIMWLK rapidity evolution of the
incoming nuclear gluon distributions. We find that the event geometry is
correlated across large rapidity intervals whereas initial state momentum
correlations are relatively short range in rapidity. Based on our results, we
discuss implications for the relevance of both effects in explaining the origin
of collective phenomena in small systems.
