Production of electron-positron pairs and rays in the collision of high density particle beams

The collision of ultrashort high-density electron-electron and positron beams on the 10s of GeV range, to be available at the FACET II facility and in near-term laser wakefield accelerator experiments (LWFA), can lead to energetic radiation (few GeVs, 1022 W/cm2) and more than 105 secondary electron-positron pairs, even for conditions where beam disruption is negligible. We propose a theoretical model for the description of beamstrahlung radiation and pair creation which occur at these interaction points. The model is confirmed by full-scale 3D self-consistent particle-in-cell simulations that include quantum electrodynamics effects. At the threshold of the quantum regime, the yield of secondary pairs is orders of magnitude higher than what is predicted by previous studies, based on the average field approximation. This yield is relevant to near-term laser wakefield (LWFA) experiments and for the design of future TeV colliders based on plasma acceleration.