Speaker
Description
In this talk I will present a framework for local subtractions of infrared singularities in hadron collider cross sections and amplitudes. The construction is guided by infrared factorization and leads to integrands in loop momentum and phase space that are suitable for integration via numerical methods.
I will focus on electroweak production via quark–antiquark annihilation at NNLO. To achieve infrared factorization for the two-loop amplitude at the local level, a careful construction of the integrand is necessary. Modifications are introduced to cure “loop polarizations” and power-like divergences, which arise in collinear limits from loop corrections to initial-state vertices and obstruct local factorization. The tools developed for amplitude integrands also guide the local subtractions at the cross section level, where initial-state singularities are factorized locally at the level of partonic integrands, while final-state singularities cancel in the sum of real and virtual contributions. All required subtraction terms are predominantly constructed from lower-order building blocks with known analytic integrals.