The three-loop singlet contribution to the massless axial-vector quark form factor

Abstract

We compute the three-loop corrections to the quark axial vector form factor in massless QCD, focusing on the pure-singlet contributions where the axial vector current couples to a closed quark loop. Employing the Larin prescription for ${\hat{I}}_5^3$, we discuss the UV renormalization of the form factor. The infrared singularity structure of the resulting singlet axial-vector form factor is explained from infrared factorization, defining a finite remainder function.

6 pages, extended discussion of renormalization