  In heavy ion collisions, transverse momentum broadening quantifies the
modification of a hard probe due to interactions with the quark-gluon plasma
(QGP). We calculate momentum broadening in the Glasma, which is the highly
non-isotropic precursor stage of the QGP right after the collision. We show
that the Glasma leads to anisotropic momentum broadening: high energy partons
accumulate more momentum along the beam axis than transverse to it. The
physical origin of anisotropic broadening can be traced back to differences in
the shapes of chromo-electric and chromo-magnetic flux tubes in the Glasma. We
provide semi-analytic results for momentum broadening in the dilute Glasma and
numerical results from real-time lattice simulations of the non-perturbative
dense Glasma.
