We have observed the production of e+e- pairs when a high energy (46.6 GeV) electron traverses the focal area of an intense (terawatt) laser pulse. From kinematic considerations alone this process involves the absorption of at least five laser photons (w=1.17 ev). Alternately one can interpret the results as the spontaneous breakdown of the vacuum induced by the electromagnetic field of the laser pulse. Indeed, in the rest-frame of the incident electron the electric field approaches the Schwinger critical value E=1.3x10¹⁶ V/cm.

Thursday, October 29th 1998, 15:30
Ernest Rutherford Physics Building, room 305