Lattice determination of the muon's anomalous magnetic moment

Informazioni relative al progetto

MUON

ID dell’accordo di sovvenzione: 101054515

DOI

10.3030/101054515

Data della firma CE 9 Dicembre 2022

Data di avvio 1 Ottobre 2023

Data di completamento 30 Settembre 2028

Finanziato da

• European Research Council (ERC)

Costo totale

€ 2 085 625,00

Contributo UE

€ 2 085 625,00

Coordinato da

FORSCHUNGSZENTRUM JULICH GMBH
Germany

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

Periodo di rendicontazione: 2023-10-01 al 2026-03-31

Sintesi del contesto e degli obiettivi generali del progetto

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.

Lavoro eseguito dall’inizio del progetto fino alla fine del periodo coperto dalla relazione e principali risultati finora ottenuti

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.

Progressi oltre lo stato dell’arte e potenziale impatto previsto (incluso l’impatto socioeconomico e le implicazioni sociali più ampie del progetto fino ad ora)

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.