Experiments on Photon-Photon Scattering

An experimental program is underway at Ecole Polytechnique to search for possible non-QED new physics in photon-photon elastic scattering at low photon energies (eV's). A two beam experiment was performed in 1995, where an IR and a green laser beam were brought to a head-on collision in vacuum, and possible scattered photons were searched for at an angle of 45$^\circ$. The first phase of an experiment with an extended discovery potential has been performed recently, in which a third beam stimulates the reaction.