Amplitude bases in generic EFTs

Abstract

We present for the first time an efficient algorithm to find a basis of kinematically independent structures built of (massless and massive) spinor helicity variables in four dimensions. This method provides a classification of independent contact terms for the scattering amplitudes with generic masses, spins, and multiplicity in any effective field theory (EFT). These contact terms are in one-to-one correspondence with a complete set of irrelevant operators in the EFT. As basic applications of our method, we classify the D2nF4 contact terms in SU(N) Yang-Mills theory for n ≤ 8, dimension-six operators involving five W±, Z and γ vector bosons, and spin-tidal effective interactions for spin-1 massive particles in gravitational theories.