Two-loop $\mathcal{N}=1$ SYM Amplitudes via SUSY Decomposition and Massive Spinor-Helicity

Abstract

We obtain a color-kinematics-dual representation of the two-loop four-vector amplitude a general renormalizable massless $\mathcal{N}=1$ SYM theory, including internal matter as chiral supermultiplets. The integrand is constructed to be compatible with dimensional regularization and supersymmetry by employing two strategies (implicitly defining our regularization scheme): supersymmetric decomposition and matching to massive spinor-helicity amplitudes. All internal vector components inherit their $D$-dimensional properties by relating them to the previously constructed $D\leq6$, $\mathcal{N}=2$ SQCD amplitude using supersymmetric decomposition identities of individual diagrams. This leaves only diagrams with internal matter lines as unknown masters, which are in turn constrained on $D$-dimensional unitarity cuts by reinterpreting the extra-dimensional momentum components as masses for the chiral supermultiplets. We rely on the massive spinor-helicity formalism and massive on-shell $\mathcal{N}=1$ superspace, generalized here to complex masses. Finally, we extend the kinematic numerator algebra to include three-term identities that are dual to color identities linear in the matter Clebsch-Gordan coefficients, as well as two new optional identities satisfied by mass-deformed $\mathcal{N}=4$ and $\mathcal{N}=2$ SYM theories that preserve $\mathcal{N}=1$ supersymmetry. Altogether, these identities makes it possible to completely reduce the two-loop integrand to only two master numerators.