QED Physics

QED contributions to four wave mixing are well studied and contribute to the Lamb shift and the anomalous electron and muon magnetic moments where they are measured very precisely. HiPER offers the opportunity to study four wave mixing beyond the lowest order where the Fermion propagators have to be evaluated in the strong field of the laser (essentially as Volkov states) and there are higher order QED and even QCD corrections to the vacuum polarisation.

HiPER also offers the opportunity to combine the ultra-intense light source with high energy electron beams created by laser acceleration in low density plasmas and therefore intrinsically synchronised with the laser pulse. With its associated electron accelerator, HiPER becomes a flexible tool to study a variety of photon scattering and pair creation processes. At an electron energy of 100GeV the Lorentz factor is 2x105 and the laser photons are upshifted by a factor of 4 2 to 160GeV. The gamma ray photons are also polarised so there is a powerful opportunity to build a (single shot!) gamma-gamma collider with photon energies up to 160GeV. It has been argued that the smallness of the photon-photon cross section is a potential window into new physics such as the existence of extra dimensions. HiPER could potentially also extend the QED pair creation studies to and particles and in principle can produce baryon pairs through QCD processes.