  Scattering amplitudes in maximally supersymmetric gauge theory receive a dual
description in terms of the expectation value of the super Wilson loop
stretched on a null polygonal contour. This makes the analysis amenable to
nonperturbative techniques. Presently, we elaborate on a refined form of the
operator product expansion in terms of pentagon transitions to compute
twist-two contributions to NMHV amplitudes. To start with, we provide a novel
derivation of scattering matrices starting from Baxter equations for flux-tube
excitations propagating on magnon background. We propose bootstrap equations
obeyed by pentagon form factors with nonsinglet quantum numbers with respected
to the R-symmetry group and provide solutions to them to all orders in 't Hooft
coupling. These are then successfully confronted against available perturbative
calculations for NMHV amplitudes to three-loop order.
