  Heavy flavour production like $J/\psi$ and $D$- meson production in
scattering of electrons/unpolarized protons off polarized proton target offer
promising probes to investigate gluon Sivers function. In this talk, I will
summarize our recent work on trasverse single spin asymmetry in $J/\psi $
-production and $D$ - meson production in $p p^\uparrow$ scattering using a
generalized parton model approach. We compare predictions obtained using
different models of gluon Sivers function within this approach and then, taking
into account the transverse momentum dependent evolution of the unpolarized
parton distribution functions and gluon Sivers function, we study the effect of
evolution on asymmetry.
