  The SLAC T-510 experiment was designed to reproduce the physics of radio
emission from air showers caused by ultra-high energy cosmic rays in a
controlled lab experiment with the goal to test established formalisms for
simulation of radio emission physics: the "end-point" formalism and the "ZHS"
formalism. Simulation results derived with these formalisms can be explained by
a superposition of magnetically induced transverse current radiation and the
Askaryan (charge-excess) effect. Here, we present results of Geant4 simulations
of the experiment with both formalisms, taking into account the details of the
experimental setup (beam energy, target geometry and material, magnetic field
configuration, and refraction effects) to test this hypothesis
