The Hadronic Contribution to the Muon Anomalous Magnetic Moment and to the Running Electromagnetic Fine Structure Constant at MZ - Overview and Latest Results

Understand

Quantum loops induce an anomaly, a_mu, in the magnetic moment of the muon that can be accurately measured.

• Its Standard Model prediction is limited in precision by contributions from hadronic vacuum polarisation of the photon.
• The dominant lowest-order hadronic term can be calculated with a combination of experimental cross section data, involving e+e- annihilation to hadrons, and perturbative QCD.
• These are used to evaluate an energy-squared dispersion integral that strongly emphasises low photon virtualities.