# The 34th International Symposium on Lattice Field Theory (Lattice 2016)

24-30 July 2016
Highfield Campus, University of Southampton
Europe/London timezone

## Lattice calculation of the pion transition form factor $\pi^0 \to \gamma^* \gamma^*$

29 Jul 2016, 18:10
20m
Building B2a Room 2077 (Highfield Campus, University of Southampton)

### Speaker

Dr Antoine Gerardin (Institute for Nuclear Physics, University of Mainz)

### Description

We report on the lattice QCD calculation of the $\pi^0 \to \gamma^\ast \gamma^\ast$ form factor using two flavors of O(a)-improved Wilson fermions with photon virtualities in the range $Q^2 \in [0-1.5]$~GeV$^2$. Different lattice spacings and pion masses are used to extrapolate our result to the physical point. First, we check that our results, once extrapolated to the chiral and continuum limit, are compatible with the chiral anomaly. Then, the shape of the form factor is compared to different phenomenological models proposed in the literature and to experimental data in the single-virtual case when one photon is on-shell. From a phenomenological point of view, this form factor determines the $\pi^0$ pole contribution to hadronic light-by-light (HLbL) scattering in the muon $g-2$,thought to be dominant.

### Primary author

Dr Antoine Gerardin (Institute for Nuclear Physics, University of Mainz)

### Co-authors

Dr Andreas Nyffeler (Institute of Nuclear Physics, University of Mainz) Prof. Harvey Meyer (Institute of Nuclear Physics, University of Mainz)

### Presentation Materials

 Slides
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