Analytic two-loop form factors in N=4 SYM

作者：Brandhuber Andreas^*; Travaglini Gabriele; Yang Gang

来源：The Journal of High Energy Physics, 2012, (5): 082.

DOI：10.1007/JHEP05(2012)082

• Supersymmetric gauge theory
• Scattering Amplitudes
• QCD

We derive a compact expression for the three-point MHV form factors of half-BPS operators in N - 4 super Yang-Mills at two loops. The main tools of our calculation are generalised unitarity applied at the form factor level, and the compact expressions for supersymmetric tree-level form factors and amplitudes entering the cuts. We confirm that infrared divergences exponentiate as expected, and that collinear factorisation is entirely captured by an ABDK/BDS ansatz. Next, we construct the two-loop remainder function obtained by subtracting this ansatz from the full two-loop form factor and compute it numerically. Using symbology, combined with various physical constraints and symmetries, we find a unique solution for its symbol. With this input we construct a remarkably compact analytic expression for the remainder function, which contains only classical polylogarithms, and compare it to our numerical results. Furthermore, we make the surprising observation that our remainder is equal to the maximally transcendental piece of the two-loop Higgs plus three-gluon scattering amplitudes in QCD.

• 出版日期2012-5