  We present an ab-initio approach to compute the longitudinal dependence of
the initial state in heavy-ion collisions by including small-x evolution of the
nuclear gluon distributions. Extending the IP-Glasma model by including JIMWLK
rapidity evolution, we compute event-by-event rapidity distributions of
produced gluons and the early time energy momentum tensor as a function of
space-time rapidity and transverse coordinates. We show how the effects of
small-x evolution manifest themselves in longitudinal (rapidity) correlations
of event-by-event multiplicities and transverse geometry and compare our
results to various phenomenological models and experimental observations.
