Lattice calculation of the hadronic light-by-light contribution to the anomalous magnetic dipole moment of muon

Date of Completion

January 2009


Physics, Theory|Physics, Elementary Particles and High Energy




The anomalous magnetic dipole moment of the muon, g-2, has been measured with great accuracy at Brookhaven National Lab. The Standard Model theory prediction for the muon g-2 is of comparable accuracy. However, a small discrepancy remains between the Standard Model prediction and the measured quantity, which may suggest possible new physics. The discrepancy is dominated by hadronic corrections, the O (α2) hadronic vacuum polarization and O (α3) hadronic light-by-light contributions. We report on a first calculation of the light-by-light contribution in full (QED+QCD) numerical simulations. We use domain wall fermions with quenched non-compact QED configurations and 2 + 1 flavor domain wall fermion plus Iwasaki gauge action QCD configurations. The results presented here consist of three non-perturbative lattice gauge theory calculations, in order of increasing difficulty: the lowest order Schwinger term which is well known in perturbation theory, the light-by-light term in pure QED which is also well known perturbatively, and finally, the full hadronic light-by-light contribution. The first two calculations address systematic uncertainties in QED lattice calculations as well as a first test of our method for computing the light-by-light term. In the latter case, we do not find a statistically significant result, but consider improved methods to achieve one with next generation computer resources. ^