Lattice determination of the muon's anomalous magnetic moment

Informations projet

MUON

N° de convention de subvention: 101054515

DOI

10.3030/101054515

Date de signature de la CE 9 Decembre 2022

Date de début 1 Octobre 2023

Date de fin 30 Septembre 2028

Financé au titre de

• European Research Council (ERC)

Coût total

€ 2 085 625,00

Contribution de l’UE

€ 2 085 625,00

Coordonné par

FORSCHUNGSZENTRUM JULICH GMBH
Germany

Periodic Reporting for period 1 - MUON (Lattice determination of the muon's anomalous magnetic moment)

Période du rapport: 2023-10-01 au 2026-03-31

Résumé du contexte et des objectifs généraux du projet

The MUON project is designed to span five years, making it a substantial undertaking with well-defined milestones and ambitious objectives. The ultimate goal remained the same as it was in the proposal, namely, significantly improve on the precision of the leading-order hadronic vacuum polarization contribution to the muon's anomalous magnetic moment by reducing its error by approximately 40%. This scientific challenge has far-reaching implications, as it seeks to answer a fundamental question: are there only four forces in nature, or is there yet another unknown interaction at play? To achieve this, a clear plan was necessary for the various computational steps. In fact, both the first year's and the second year's achievements exceeded many of the original milestone expectations.

In year one and year two one of the most crucial and time-consuming tasks is the detailed scientific planning, which involves thorough literature reviews, discussions with international colleagues, and informed decision-making regarding the research steps. In the field of lattice QCD, this last step is particularly critical, as a suboptimal decision about simulation parameters can significantly prolong the project timeline by doubling or tripling it.

A significant amount of time and effort was dedicated to producing a main paper, arXiv:2407.10913 [hep-lat] and to its revised versions, for which I am the corresponding author. The paper spans now close to 100 pages and represents a substantial undertaking. Despite being quite a new paper, it has already generated an impressive 120+ citations.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

The main result of the above mentioned paper is a new determination of the leading order hadronic vacuum polarization to the magnetic moment of the muon. The experimental uncertainty is 1.5e-10 and the theoretical one ist 3.3e-10. The two results show perfect agreement within the uncertainties. This means an eleven digit agreement. The theoretical result is based on four major ingredients: (a) the "tree level result of Dirac"; (b) the high loop calculation of quantum electrodynamics (c) the contribution of the weak interaction with spontaneous symmetry breaking; (d) the non-perturbatively formulated and renormalized strong interaction from the lattice. These are very different forms of quantum results and the astonishing agreement between experiment and theory proves that quantum field theory is correct at least up to 11 digits. This is the strongest proof what we have today.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

The agreement or non-agreement of theory and experiment is a question of uncertainties. Our theoretical method and result is the most precise one in the literature.