A planar four-loop form factor and cusp anomalous dimension in QCD

Understand

We compute the fermionic contribution to the photon-quark form factor to four-loop order in QCD in the planar limit in analytic form.

• From the divergent part of the latter the cusp and collinear anomalous dimensions are extracted.
• Results are also presented for the finite contribution.
• We briefly describe our method to compute all planar master integrals at four-loop order.