Anomalous pinch in electron-electron beam collision

We show that an anomalous pinch can occur in ultrarelativistic electron-electron or positron-positron beam interaction, caused by the combined interplay of collective beam motion (disruption) and strong-field quantum electrodynamics (SF-QED). The locally created electron-positron pairs, from SF-QED effects, screen the self-fields of the beams and can invert the polarity of the Lorentz force resulting in a pinch of the beams. A theoretical model predicts the pinch condition and is confirmed by first-principles 3-dimensional particle-in-cell simulations. This anomalous pinch enhances density compression, increases the collision luminosity, and amplifies the local magnetic fields and the quantum parameter of the beam particles by several orders of magnitude.