# The 16th International Workshop on Tau Lepton Physics (TAU2021) (Virtual Edition)

September 27, 2021 to October 1, 2021
Indiana University
America/Indiana/Indianapolis timezone

## Two-pion contribution to hadronic vacuum polarization

Sep 30, 2021, 2:00 PM
20m
Virtual (Indiana University)

### Virtual

#### Indiana University

Oral contribution

### Speaker

Peter Stoffer (University of Zurich)

### Description

The largest part of the hadronic-vacuum-polarization (HVP) contribution to the muon anomalous magnetic moment is due to the intermediate state of two pions. Analyticity and unitarity do not only allow us to write this contribution in terms of the pion vector form factor (VFF), but also constrain the VFF itself. I will discuss fits of a dispersive representation of the pion VFF to $e^+e^-$ cross-section data and I will comment on the implications of analyticity and unitarity in view of the tension between data-driven evaluations of HVP and recent lattice-QCD results.

### Primary authors

Peter Stoffer (University of Zurich)