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arXiv · 2610.28283

Automation of amplitude-level QED resummation with ACRAIC

Alan Price
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Abstract

Precision electroweak predictions for future $e^+e^-$ colliders will require levels of precision unmatched in collider physics and the modelling of multiple-photon emissions, and the exponentiation of the associated logarithms needs to be carefully considered. The Yennie-Frautschi-Suura theorem subtracts the infrared singularities to all orders and exponentiates them, leaving infrared-finite remainders which can be calculated order-by-order. Coherent exponentiation performs this subtraction at the amplitude level, preserving the interference between emissions, but has so far been available only for fermion-pair production, with hand-coded amplitudes. We present ACRAIC, an automated, amplitude-level realization of this subtraction for general scattering processes in Sherpa. This method allows us to construct an $\mathcal{O}(α)$ and $\mathcal{O}(α^2)$ amplitude level subtraction scheme, in which the infrared-finite remainders are tree-level helicity amplitudes with partition-dependent propagator shifts, computed by the Berends--Giele recursion, and the one-loop electroweak virtual enters through a per-helicity factor from the loop provider. At $\mathcal{O}(α^2)$ two independent matchings agree on the size of the missing higher orders to $\sim10^{-3}$, and the estimated perturbative uncertainty shrinks by about an order of magnitude relative to $\mathcal{O}(α)$.

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Alan Price. 2026-10-20. Automation of amplitude-level QED resummation with ACRAIC. https://arxiv.org/abs/2610.28283

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