High-precision calculation of the 4-loop QED contribution to the slope of the Dirac form factor

Understand

We have evaluated with 1100 digits of precision the contribution of all the 891 mass-independent four-loop Feynman diagrams contributing to the slope of the Dirac form factor in QED.

• The total 4-loop contribution is $ m^2 F_1^{(4)'}(0) = 0.886545673946443145836821730610315359390424032660064745...
• \left(\frac{\alpha}{\pi}\right)^4$.
• We have fit a semi-analytical expression to the numerical value.