Enhanced creation of high energy particles in colliding laser beams

The creation of particles by two colliding strong laser beams is considered. It is found that the electron-positron pairs created in the laser field via the Schwinger mechanism may recollide after one or several oscillations in the field. Their collision can take place at high energy, which the pair gains from the field. As a result, high energy gamma quanta can be created by inelastic scattering or annihilation of the pair. Moreover, heavy particles such as muon pairs may also be created via the annihilation $e^+ + e^-\rightarrow \mu^+ + \mu^- $. The probability of $e^-e^+$ collision is greatly enhanced due to a strong alignment of the electron and positron momenta with the electric field. The found muon creation rate exponentially exceeds the rate predicted by the direct Schwinger mechanism for muons, while the photon creation rate exponentially exceeds photon emission due to the fermion oscillation.