  Electron-plasmon coupling in graphene has recently been shown to give rise to
a "plasmaron" quasiparticle excitation. The strength of this coupling has been
predicted to depend on the effective screening, which in turn is expected to
depend on the dielectric environment of the graphene sheet. Here we compare the
strength of enviromental screening for graphene on four different substrates by
evaluating the separation of the plasmaron bands from the hole bands using
Angle Resolved PhotoEmission Spectroscopy. Comparison with G0W-RPA predictions
are used to determine the effective dielectric constant of the underlying
substrate layer. We also show that plasmaron and electronic properties of
graphene can be independently manipulated, an important aspect of a possible
use in "plasmaronic" devices.
