Electron-positron pair production by linear Breit-Wheeler process in ultra-short petawatt laser-plasma interaction

In this work, we have demonstrated with a help of particle-in-cell simulations that an ultra-short petawatt laser light self-organizes a photon collider in a near critical over-dense plasma and produces a large number of positrons via the linear Breit-Wheeler (BW) process. An ultra- intense laser pulse propagates in an over dense plasma by its relativistic transparency with forming a magnetic channel structure and accumulating electrons in front of the pulse. In the magnetic channel, the laser light drives relativistic electrons and induces collimated gamma-ray photons via synchrotron radiation. While at the pulse front electrons are accelerated backward with relativistic energies by an electrostatic field induced by the electron accumulation. The relativistic electrons moving backward emit photons when they collide the laser pulse. These photons collide with the gamma-ray photons and induce electron-positron pairs via the BW process. We also found that the generated positrons are accelerated by the electrostatic field to GeV energy with a narrow divergence of ±10 degrees. In the talk, we'll report the physics of the collider formation and details of the simulation results.