Bhabha scattering at NNLO with next-to-soft stabilisation

Understand

A critical subject in fully differential QED calculations originates from numerical instabilities due to small fermion masses that act as regulators of collinear singularities.

• At next-to-next-to-leading order (NNLO) a major challenge is therefore to find a stable implementation of numerically delicate real-virtual matrix elements.
• In the case of Bhabha scattering this has so far prevented the development of a fixed-order Monte Carlo at NNLO accuracy.
• In this paper we present a new method for stabilising the real-virtual matrix element.