Charge-neutral, GeV-scale electron-positron pair beams produced using bremsstrahlung gamma rays

Matter-antimatter plasmas, such as electron-positron pair plasmas, are frequently observed in various astrophysical phenomena. In laboratory settings, electron-positron pairs have often been generated using high-Z converters irradiated by either direct laser pulses or laser-driven electron beams. Here we generate charge-neutral electron-positron beams with energies in the GeV range, utilizing bremsstrahlung gamma rays. Specifically, intense high-energy gamma rays produced electron-positron pair particles in a lead converter via the Bethe-Heitler process. The produced pair beams exhibited neutrality across all converter thicknesses throughout the energy spectrum spanning from 10 MeV to 1.8 GeV. Pairs with energies surpassing 1 GeV constituted up to 26% of the total kinetic energy within the spectrum. The experimental results were in good agreement with our Geant4 Monte Carlo simulations. These GeV-scale neutral pair particle beams have potential applications for understanding energetic astrophysical phenomena and high-energy particle physics.