Nonlinear quantum electrodynamic processes have been studied in the presence of an intense electromagnetic field.[1] Nonlinear Compton scattering and electron-positron pair production from photon-photon interactions have been observed. Both processes require multiphoton interactions with the electromagnetic field, hence require that the normalized electric field, h=Erms/mwc, be of order one. Erms is the rms value of the laser electric field and w is the laser frequency. Pair production requires, in addition, that the laser field be comparable to the QED critical field (Ecr=1.6 X 10 16 V/cm, or I 1029W/cm2) The experiments were carried out by colliding a 1.053mm or 0.527mm wavelength laser beam with intensities up to 1018W/cm2 with 46.6 or 49.1 GeV electrons at the Final Focus Test Beam at the Stanford Linear Accelerator Center.
These experiments represent the first observations of multiphoton-electron and multiphoton-photon scattering as well as the first observation of the production of particles with mass from the scattering of real photons!
· representing the E-144 collaboration, Princeton University, University of Rochester, University of Tennessee, and Stanford Linear Accelerator Center.
[1] D.L. Burke et al. Phys. Rev. Lett. 79 1626 (1997)