A nice two-loop next-to-next-to-MHV amplitude in N $$ \mathcal{N} $$ = 4 super-Yang-Mills

Abstract

Abstract We study a scalar component of the 8-point next-to-next-to-maximally-helicity-violating (N2MHV) amplitude at two-loop level in N $$ \mathcal{N} $$ = 4 super-Yang-Mills theory; it has a leading singularity proportional to the inverse of the four-mass-box square root and receives contributions from only two types of non-trivial integrals with one-loop infrared (IR) divergences. We compute such two-loop 8-point integrals by taking (double-)collinear limits of certain finite, dual-conformal-invariant integrals, and they nicely give the IR-safe ratio function after subtracting divergences. As the first genuine two-loop N2MHV amplitude computed explicitly, we find remarkable structures in its symbol and alphabet: similar to the next-to-MHV (NMHV) case, there are still 9 algebraic letters associated with the square root, and the latter also becomes a letter for the first time; unlike the NMHV case, such algebraic letters appear at either one or all of the second, third and last entry, and the part with three odd letters is particularly simple.

Keywords

• Scattering Amplitudes
• Supersymmetric Gauge Theory