Atlas observes light scattering off light
Light by light scattering was first observed at SLAC in the mid 90s by experiment E-144.https://physicsworld.com/a/light-is-seen-to-scatter-off-ligh...Link to paper from 1997:
Positron Production in Multiphoton Light-by-Light Scattering(published in Phys. Rev. Lett., Vol. 79, p. 1626 (1997).)
http://www.slac.stanford.edu/exp/e144/ps/positron_slacpub.ps