  Relativistic nuclear collisions offer a unique way to study strong
interactions at very high energy. The collision process can be described within
the gluon saturation framework as the interaction of two colored glasses, and
because of this interaction strong longitudinal gluon fields, namely the
Glasma, are produced immediately after the collision. Besides, heavy quarks are
also produced in the very early stage and because of their large mass and small
concentration, their motion does not affect the evolution of the Glasma, thus
behaving as ideal probes of the Glasma itself. We study the evolution of the
heavy quarks in the Glasma allegedly produced in high energy p-Pb collisions by
solving consistently the equations of motion of the quarks in the evolving
Glasma fields. We find that this motion can be understood in terms of diffusion
in momentum space, similarly to the random motion of a heavy probe in a hot
thermalized medium. We show how the diffusion of heavy probes affects the
nuclear modification factor of D and B mesons in p-Pb collisions.
