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arXiv · 2106.07469

Bhabha scattering at NNLO with next-to-soft stabilisation

Pulak Banerjee·Tim Engel·Nicolas Schalch·Adrian Signer·Yannick Ulrich
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Abstract

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. It is based on the expansion for soft photon energies including the non-universal subleading term calculated with the method of regions. We have applied this method to Bhabha scattering to obtain a stable and efficient implementation within the McMule framework. We therefore present for the first time fully differential results for the photonic NNLO corrections to Bhabha scattering.

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Pulak Banerjee, Tim Engel, Nicolas Schalch, Adrian Signer, Yannick Ulrich. 2021-06-14. Bhabha scattering at NNLO with next-to-soft stabilisation. https://doi.org/10.1016/j.physletb.2021.136547

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