El-Khadra oversaw the theoretical aspects of the Muon g-2 experiments. The collaboration measured the magnetic moment of the muon with unparalleled precision. El-Khadra has been involved with several theoretical attempts to predict the anomalous magnetic moment based on the Standard Model. In 2021, the experimental component of the collaboration reported a magnetic moment that was considerably larger than the value predicted by the Standard Model. This finding hints at new particles or forces in the Standard Model.