Proposal for a STUDY OF QED AT CRITICAL FIELD STRENGTH IN INTENSE LASER–HIGH ENERGY ELECTRON COLLISIONS AT THE STANFORD LINEAR ACCELERATOR

Executive Summary We propose a program of study of the interaction of electrons and photons in fields approaching the critical QED field strength of an electron rest energy per Compton wavelength. This can be achieved in collisions between the picosecond pulses of a teraWatt laser and a 50-GeV electron beam. The phenomena accessible to study include nonlinear Compton scattering , trident production, and Breit-Wheeler pair production. The electric field at the laser focus is of similar strength to that of an electron bunch in future linear colliders, permitting a close analog of beamstrahlung to be studied. Measurement of the invariant-mass spectrum of electron-positron pairs could clarify whether the positron peaks seen at Darmstadt in heavy-ion collisions are a strong-field QED effect. Electron-laser collisions at critical field strength may prove to be a high-brightness source of positrons for future colliders.