  The origin of weakly-bound nuclear clusters in hadronic collisions is a key
question to be addressed by heavy-ion collision (HIC) experiments. The measured
yields of clusters are approximately consistent with expectations from
phenomenological statistical hadronisation models (SHMs), but a theoretical
understanding of the dynamics of cluster formation prior to kinetic freeze out
is lacking. The competing model is nuclear coalescence, which attributes
cluster formation to the effect of final state interactions (FSI) during the
propagation of the nuclei from kinetic freeze out to the observer. This
phenomenon is closely related to the effect of FSI in imprinting femtoscopic
correlations between continuum pairs of particles at small relative momentum
difference. We give a concise theoretical derivation of the
coalescence--correlation relation, predicting nuclear cluster spectra from
femtoscopic measurements. We review the fact that coalescence derives from a
relativistic Bethe-Salpeter equation, and recall how effective quantum
mechanics controls the dynamics of cluster particles that are nonrelativistic
in the cluster centre of mass frame. We demonstrate that the
coalescence--correlation relation is roughly consistent with the observed
cluster spectra in systems ranging from PbPb to pPb and pp collisions. Paying
special attention to nuclear wave functions, we derive the coalescence
prediction for hypertriton and show that it, too, is roughly consistent with
the data. Our work motivates a combined experimental programme addressing
femtoscopy and cluster production under a unified framework. Upcoming pp, pPb
and peripheral PbPb data analysed within such a programme could stringently
test coalescence as the origin of clusters.
