HEP Theory Journal Club

Bootsrapping 2-loop 5-gluon amplitudes from kinematical limits

Mathieu Giroux

McGill

As the CERN’s Large Hadron Collider (LHC) is about to start its third run in 2021, a new era of precision measurements is dawning in front of us. To fully exploit the machine's potential, accurate theoretical predictions are required. These can be obtained through the computation of higher orders in perturbation theory. Unfortunately, for many QCD processes, next-to-leading-order (NLO) precision is insufficient due to the large theoretical uncertainty. At present, only observables involving up to 4 particles are fully available at NNLO. However, at 2-loop, some crucial information is known about 5-parton amplitudes. They all relate to a common set of master integrals (minimal IBP basis): the massless on-shell 5-point functions at 2 loops, which can be evaluated from the canonical differential equations (DE) method. The 5-gluon amplitude is consequently the appropriate theoretical starting point toward analytic results for genuine virtual corrections to 2 -> 3 amplitudes in QCD. In particular, in this talk, I will argue that there exists a web of “highways” in the kinematic space allowing one to recover non-planar 2-loop 5-gluon amplitudes efficiently, from just 1 initial configuration of the external gluons. The upshot is that we think these “highways” are fully determined by how extreme kinematic limits talk to each other.