Feynman diagrams representing processes contributing to the muon's anomalous magnetic moment.
In each diagram, the bottom photon represents coupling to the external magnetic field B.
The first three are standard-model contributions:
(a) A single virtual-photon loop gives the leading QED term.
(b) Virtual hadron pairs contribute to vacuum polarization.
(c) A loop with virtual W bosons and a neutrino contributes to electroweak radiative corrections.
(d) Beyond the standard model, a conjectural contribution involves a sneutrino () loop.
The virtual chargino ()
is a superposition of the supersymmetric partners of the Higgs and W bosons.