  We study the diffusion of charm and beauty in the early stage of high energy
nuclear collisions at RHIC and LHC energies, considering the interaction of
these heavy quarks with the evolving Glasma by means of the Wong equations. In
comparison with previous works, we add the longitudinal expansion as well as we
estimate the effect of energy loss due to gluon radiation. We find that heavy
quarks diffuse in the strong transverse color fields in the very early stage
(0.2-0.3 fm/c) and this leads to a suppression at low $p_T$ and enhancement at
intermediate low $p_T$. The shape of the observed nuclear suppression factor
obtained within our calculations is in qualitative agreement with the
experimental results of the same quantity for $D-$mesons in proton-nucleus
collisions. We compute the nuclear suppression factor in nucleus-nucleus
collisions as well, for both charm and beauty, finding a substantial impact of
the evolving Glasma phase on these, suggesting that initialization of heavy
quarks spectra in the quark-gluon plasma phase should not neglect the early
evolution in the strong gluon fields.
