
Johan Bijnens and Johan Relefors
Pion lightbylight contributions to the muon g2
Abstract
This paper contains some new results on the hadronic lightbylight contribution (HLbL) to the muon g−2. The first part argues that we can expect large effects from disconnected diagrams in present and future calculations by lattice QCD of HLbL. The argument is based on the dominance of pseudoscalar meson exchange.In the second part, we revisit the pion loop HLbL contribution to the muon anomalous magnetic moment. We study it in the framework of some models studied earlier, pure pion loop, full VMD and hidden local symmetry for inclusion of vector mesons. In addition we study possible ways to include the axialvector meson. The main part of the work is a detailed study of how the different momentum regions contribute. We derive a short distance constraint on the γ∗γ∗→ππ amplitude and use this as a constraint on the models used for the pion loop. As a byproduct we present the general result for integration using the Gegenbauer polynomial method.
LU TP 1644
