
Johan Bijnens, Nils HermanssonTruedsson, Antonio RodrÃguezSÃ¡nchez
Shortdistance constraints for the HLbL contribution to the muon anomalous magnetic moment
Abstract
We derive shortdistance constraints for the hadronic lightbylight contribution (HLbL) to the anomalous magnetic moment of the muon in the kinematic region where the three virtual momenta are all large. We include the external soft photon via an external field leading to a welldefined Operator Product Expansion. We establish that the perturbative quark loop gives the leading contribution in a well defined expansion. We compute the first nonzero power correction. It is related to to the magnetic susceptibility of the QCD vacuum. The results can be used as modelindependent shortdistance constraints for the very many different approaches to the HLbL contribution. Numerically the power correction is found to be small.
LU TP 1938
