  We propose to study the partonic structure of $^4$He by measuring the Beam
Spin Asymmetry (BSA) in coherent Deeply Virtual Compton Scattering (DVCS) and
the differential cross-section of the Deeply Virtual Meson Production (DVMP) of
the $\phi$. Despite its simple structure, a light nucleus such as $^4$He has a
density and a binding energy comparable to that of heavier nuclei. Therefore,
by studying $^4$He nucleus, one can learn typical features of the partonic
structure of atomic nuclei.
  The combination of CLAS12 and the ALERT detector provides a unique
opportunity to study both the quark and gluon structure of a dense light
nucleus. Coherent exclusive DVCS off $^4$He will probe the transverse spatial
distribution of quarks in the nucleus as a function of the quarks' longitudinal
momentum fraction, $x$. In parallel, the average spatial transverse gluon
density of the $^4$He nucleus will be extracted within a GPD framework using
the measured longitudinal cross-section for coherent $\phi$ production in a
similar range of $x$. Additionally, threshold effects of $\phi$ production can
be explored by exploiting the ALERT detector's large acceptance for low $|t|$
events.
