LBL – Light-by-light scattering

Project leaders


  • Dr. Kristof Schmieden
  • Prof. Dr. Matthias Schott


The direct observation of the \(\gamma \gamma \to \gamma \gamma\) (LbL) process at the ATLAS and CMS experiments at the LHC has opened a new channel for testing the Standard Model.

With the increased precision of the future LHC Run 3 and 4 measurements, one hopes to access exotic mesons, as well as hadronic effects in general. We will provide dedicated theoretical and experimental support for these new measurements. A further aim here is to study the hadronic resonances in the heavy quark sector. We will potentially discover new states and provide an accurate determination of the \(\gamma\gamma\) decay width for the established states.

From the direction of lattice QCD we  plan to generate high-quality lattice data on the eight forward hadronic LbL scattering amplitudes, including their isospin decomposition. We will compare these lattice-determined LbL amplitudes to their respective predictions based on the dispersive
sum rules for LbL scattering, and thereby determine or constrain the \(\gamma^\ast \gamma^\ast \) couplings of scalar, axial-vector and tensor mesons