Production of relativistic pairs and hard photons in beam-beam collisions*

The upgrade of the linear collider at SLAC (FACET II) and the next generation of laser wakefield accelerators (LWFA) will deliver high current ultrashort round bunches capable of reaching the quantum regime at 10s of GeV. We investigate the collision of these beams envisaging a secondary source of collimated gamma-ray photons and ultrarelativistic pairs. We determine the photon spectrum and the secondary pairs yield both analytically and with PIC simulations with OSIRIS-QED. Our analytical model and the simulations show excellent agreement. The configuration of the collective fields favors the quantum effects to take place in a localized region resulting in a yield of secondary pairs considerably higher than what previously predicted. Our results demonstrate the potential of this setup as a secondary source of radiation and of relativistic pairs.