Two-Flavor QCD Correction to Lepton Magnetic Moments at Leading Order in the Electromagnetic Coupling

Abstract

We present a reliable nonperturbative calculation of the QCD correction, at leading order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon, and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes, and a broad range of quark masses to control the continuum, infinite-volume, and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modification to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513(43)×10(-12), 5.72(16)×10(-8), and 2.650(54)×10(-6) for the leading-order two-flavor QCD correction to the anomalous magnetic moment of the electron, muon, and tau, respectively, each accurate to better than 3%.

Finite-volume electromagnetic corrections to the masses of mesons, baryons, and nuclei

“…As upcoming experiments, Fermilab E989 and J-PARC E34, plan to reduce the experimental uncertainty down to 0.14 ppm, theoretical calculations of non-perturbative hadronic contributions must be refined in the short term. LQCD is expected to contribute to improving the theoretical prediction of the standard model, and several recent efforts have been directed at obtaining the hadronic vacuum-polarization and hadronic light-by-light contributions to the muon g − 2 [68][69][70][71][72][73][74][75][76][77][78]. Theoretical challenges facing these calculations have been identified and will be addressed during the next few years.…”

Muon g − 2 vs LHC in supersymmetric models

“…The evaluations of the hadronic light-by-light contribution have been improving (see ref. [65] for a recent review), and lattice calculations are in development [66][67][68][69][70][71]. If the anomaly is confirmed in future, SUSY is one of the most attractive candidates for the solution.…”

Computing the hadronic vacuum polarization function by analytic continuation

“…In addition, a number of approaches have been employed to describe the HVP function on the lattice. Here, well-motivated [5][6][7][8][9][10] or even model-independent [11] functional forms to fit the results computed at discrete lattice momenta have been used. They lead to smooth functions that describe well the desired momentum region, including zero momentum, needed to obtain the renormalized HVP function.…”