STATUS OF HADRONIC LIGHT-BY-LIGHT SCATTERING IN THE MUON g – 2

We give an update on the status of the hadronic light-by-light scatteringcontribution to the muon g-2. We review recent work by various groups, listsome of the open problems and give an outlook on how to better control theuncertainty of this contribution. This is necessary in order to fully profitfrom planned future muon g-2 experiments to test the Standard Model. Despitesome recent developments, we think that the estimate a_{mu}^{HLbL} = (116 \pm40) x 10^{-11} still gives a fair description of the current situation.Comment: 9 pages, 2 figures, based on presentations at PHIPSI13, Rome; Working Group on Radiative Corrections and Monte Carlo Generators for Low Energies, Frascati; LC13, Trento, September 201