Shedding some light on the light-by-light

by Dr Oscar Catà (Siegen U.)

Thursday 25 Feb 2021, 12:00 → 13:00 Europe/Madrid

IFAE Virtual Seminar Room (IFAE)

 The evaluation of the hadronic light-by-light (HLbL) contribution to the (g-2)_mu is hindered by our limited knowledge of QCD below the confinement scale, where resonances play a major role. Different hadronic models have been proposed in the past to estimate it, where contact with QCD is achieved by fulfilling a varying number of short-distance constraints. Particularly problematic is the so-called Melnikov-Vainshtein (MV) constraint, which is hard to incorporate in hadronic models. In this talk I will use a 5-dimensional model to show that the MV constraint arises from a collective effect of axial resonances and it is a manifestation of the axial anomaly. In light of this result, I will also revisit the Goldstone- and axial-exchange contributions to the HLbL.

IFAE_HLbL.pdf