What it takes to calculate the magnetic moment of the muon in the standard model

by Stefan Leupold (Uppsala University)

Thursday 5 Sept 2019, 14:00 → 15:00 Europe/Stockholm

Beurlingrummet (Ångstrom)

The magnetic moment of the muon is the observable which shows at the moment the largest discrepancy between experiment and standard-model prediction (3 to 4 standard deviations) [1]. To turn the indication to an observation requires the reduction of both experimental and standard-model uncertainty. The dominant source of the latter resides in the hadronic contributions that enter the magnetic moment via loop corrections that involve strongly interacting fields. At the present level of accuracy the main players are the hadronic vacuum polarization and the hadronic light-by-light (HLbL) scattering contribution. I will report how dispersion theory can be used to relate the hadronic contributions to measurable quantities and obtain in that way a data driven determination including a reliable uncertainty estimate. In particular, I will focus on the most recent determination of the leading contribution to HLbL emerging from the pion-pole diagram [2,3]. 

[1] F. Jegerlehner and A. Nyffeler, Phys. Rept. 477, 1 (2009)

[2] M. Hoferichter, B. L. Hoid, B. Kubis, S. Leupold and S. P. Schneider, Phys. Rev. Lett. 121, 112002 (2018)

[3] M. Hoferichter, B. L. Hoid, B. Kubis, S. Leupold and S. P. Schneider, JHEP 1810, 141 (2018)