Chiral extrapolation of the leading hadronic contribution to the muon anomalous magnetic moment

Understand

A lattice computation of the leading-order hadronic contribution to the muon anomalous magnetic moment can potentially help reduce the error on the Standard Model prediction for this quantity, if sufficient control of all systematic errors affecting such a computation can be achieved.

• One of these systematic errors is that associated with the extrapolation to the physical pion mass from values on the lattice larger than the physical pion mass.
• We investigate this extrapolation assuming lattice pion masses in the range of 200 to 400MeV with the help of two-loop chiral perturbation theory, and find that such an extrapolation is unlikely to lead to control of this systematic error at the 1% level.
• This remains true even if various tricks to improve the reliability of the chiral extrapolation employed in the literature are taken into account.