Observing multiphoton electron–positron pair production (the nonlinear Breit–Wheeler process) requires high-energy γ rays to interact with strong electromagnetic fields. In order for these observations to be as precise as possible, the γ rays would ideally be both mono-energetic and highly polarized. Here we perform Monte Carlo simulations of an experimental configuration that accomplishes this in two stages. First, a multi-GeV electron beam interacts with a moderately intense laser pulse to produce a bright, highly polarized beam of γ rays by inverse Compton scattering. Second, after removing the primary electrons, these γ rays collide with another, more intense, laser pulse in order to produce pairs. We show that it is possible to measure the γ-ray polarization dependence of the nonlinear Breit–Wheeler process in near-term experiments, using a 100 TW class laser and currently available electron beams. Furthermore, it would also be possible to observe harmonic structure and the perturbative-to-nonperturbative transition if such a laser were colocated with a future linear collider.
This paper explores a method to precisely observe the creation of electron-positron pairs from high-energy, polarized gamma rays. By using a high-energy electron beam and two powerful laser pulses, the researchers can generate a bright, highly polarized gamma ray beam and then collide it with another laser to produce the pairs.