Chiral extrapolation of hadronic vacuum polarization

We study the pion-mass dependence of two-pion channel in hadronic-vacuum-polarization (HVP) contribution to anomalous magnetic moment muon a?HVP, by using an Omnès representation for pion vector form factor with phase shift derived from inverse-amplitude method (IAM). Our results constrain dominant isospin-1 part isospin-symmetric light-quark contribution, and should thus allow one better control chiral extrapolation required lattice-QCD calculations performed at larger-than-physical masses. In particular, comparison one- two-loop IAM allows us estimate associated systematic uncertainties show that these are under good control.