### INT Workshop INT-19-74W

## Hadronic contributions to (g-2)_{μ}

### September 9 - 13, 2019

## Overview

The deviation between measurement and Standard-Model (SM) prediction of the anomalous magnetic moment of the muon is one of the few current persistent hints for physics beyond the SM. Because the muon g-2 arises from quantum-mechanical loop contributions in the SM, it is sensitive to virtual effects of new particles, and places important constraints on SM extensions. To leverage the anticipated reduction in the experimental errors of a factor of 4 at the Fermilab E989 experiment, and determine unambiguously whether or not New-Physics effects contribute to this quantity, the theoretical errors must be made more reliable and reduced to a commensurate level. The dominant sources of uncertainty in the SM prediction of the muon g-2 are from the hadronic corrections, in particular, from the hadronic vacuum polarization and hadronic light-by-light scattering contributions. There are a number of complementary theoretical efforts underway to better understand and quantify these hadronic corrections, including dispersive and data-driven methods, lattice QCD, and effective field theories.

## Muon g-2 Theory Initiative:

The Muon g-2 Theory Initiative was formed to facilitate interactions between these different
groups, as well as between the theoretical and experimental g-2 communities. Given the precision
goals and the stakes, fostering the development of several independent methods for each of the two
hadronic corrections with fully quantified uncertainties is an important goal of the initiative, as it will
enable critical cross checks, and, upon combination, may yield gains in precision, to maximize the
impact of E989 and the planned J-PARC E34 experiment.

This workshop will be the third plenary meeting of the initiative. Given the anticipated release of first results of E989 in 2019,
the meeting will kick-off the second stage of the Initiative, the key point being the development of strategies to go beyond a consolidation of the SM prediction at the level of the BNL results
and determine the hadronic contributions at a level of the final goal of the E989 experiment. The workshop, while focused on the hadronic corrections for the muon g-2, will also consider relations to the g-2 of the electron as well as electroweak contributions.

## Workshop format:

We will follow the format of previous Muon g-2 Theory Initiative workshops, featuring a mix of talks and discussion sessions. A workshop registration fee of $55 will apply. The registration fee includes participation in the workshop, lectures, and coffee breaks.

*
*