  We exploit GaAs-based quantum point contacts as mesoscopic detectors to
analyze the ballistic flow of photogenerated electrons in a two-dimensional
electron gas at a perpendicular magnetic field. Whereas charge transport
experiments always measure the classical cyclotron radius, we show that this
changes dramatically when detecting the photoinduced non-equilibrium current in
magnetic fields. The experimentally determined radius of the trajectories
surprisingly exceeds the classical cyclotron value by far. Monte Carlo
simulations suggest electron-electron scattering as the underlying reason.
