  Dihadron angular correlations in forward $pA$ collisions have been considered
as one of the most sensitive observables to the gluon saturation effects. In
general, both parton shower effects and saturation effects are responsible for
the back-to-back dihadron angular de-correlations. With the recent progress in
the saturation formalism, we can incorporate the parton shower effect by adding
the corresponding Sudakov factor in the saturation framework. In this paper, we
carry out the first detailed numerical study in this regard, and find a very
good agreement with previous RHIC $pp$ and $dAu$ data. This study can help us
to establish a baseline in $pp$ collisions which contains little saturation
effects, and further make predictions for dihadron angular correlations in
$pAu$ collisions, which will allow to search for the signal of parton
saturation.
