The anomalous magnetic moment of the muon in the Standard Model
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Abstract
We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant α and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including O(α5) with negligible numerical uncertainty. The electroweak contribution is suppressed by (mμ∕MW)2 and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at O(α2) and is due to hadronic vacuum polarization, whereas at O(α3) the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads aμSM=116591810(43)×10−11 and is smaller than the Brookhaven measurement by 3.7σ. The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future – which are also discussed here – make this quantity one of the most promising places to look for evidence of new physics.
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The record
- Venue
- Physics Reports
- Topic
- Computational Physics and Python Applications
- Field
- Computer Science
- Canadian institutions
- —
- Funders
- Coordinación de la Investigación CientíficaFundação para a Ciência e a TecnologiaJapan Society for the Promotion of ScienceNatural Sciences and Engineering Research Council of CanadaScience and Technology Facilities CouncilHorizon 2020 Framework ProgrammeOffice of ScienceEuropean Research CouncilNational Institute of Standards and TechnologyDanmarks Frie ForskningsfondNuclear PhysicsJunta de AndalucíaHelmholtz AssociationAgence Nationale de la RechercheMinistry of Education and Research, RomaniaCentre National de la Recherche ScientifiqueU.S. Department of EnergyVetenskapsrådetMinisterio de Economía y CompetitividadNational Research FoundationHigh Energy Accelerator Research OrganizationEuropean CommissionMinisterio de Ciencia e InnovaciónIstituto Nazionale di Fisica NucleareGeneralitat de CatalunyaBundesministerium für Bildung und ForschungIsaac Newton TrustStrongSchweizerischer Nationalfonds zur Förderung der Wissenschaftlichen ForschungConsejo Nacional de Ciencia y TecnologíaMinistry of Science and Higher Education of the Russian FederationUniversidad Michoacana de San Nicolás de HidalgoHigh Energy PhysicsDeutsche ForschungsgemeinschaftFermilabNational Science FoundationUniversity of WashingtonRussian Science FoundationLeverhulme TrustUniversity of ConnecticutAix-Marseille Université
- Keywords
- Anomalous magnetic dipole momentHadronElectroweak interactionMuonDispersion relationStandard Model (mathematical formulation)ScatteringMoment (physics)
- Has abstract in OpenAlex
- yes