A note on NMHV form factors from the Grassmannian and the twistor string

In this note we investigate Grassmannian formulas for form factors of the chiral part of the stress-tensor multiplet in N=4 superconformal Yang-Mills theory. We present an all-n contour for the G(3, n + 2) Grassmannian integral of NMHV form factors derived from on-shell diagrams and the BCFW recursion relation. In addition, we study other G(3, n + 2) formulas obtained from the connected prescription introduced recently. We find a recursive expression for all n and study its properties. For n >= 6, our formula has the same recursive structure as its amplitude counterpart, making its soft behaviour manifest. Finally, we explore the connection between the two Grassmannian formulations, using the global residue theorem, and find that it is much more intricate compared to scattering amplitudes.