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  • Open Access

Double Spacelike Collinear Limits from Multi-Regge Kinematics

Claude Duhr*, Aniruddha Venkata†, and Chi Zhang (张驰)‡

  • *Contact author: cduhr@uni-bonn.de
  • †Contact author: avenkata@uni-bonn.de
  • ‡Contact author: czhang@uni-bonn.de
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Phys. Rev. Lett. 135, 241601 – Published 9 December, 2025

DOI: https://doi.org/10.1103/3bxb-zfwc

Abstract

We study scattering amplitudes and form factors in planar N=4 super Yang-Mills theory in the limit where two pairs of gluons become collinear. We find that, when the virtualities of both collinear pairs are spacelike, the collinear factorization of the amplitude involves a generalized splitting amplitude that correlates the two collinear directions, confirming a recent proposal in the literature. Remarkably, we find that our generalized splitting amplitude agrees with the Bern-Dixon-Smirnov subtracted six-point amplitude in multi-Regge kinematics. The latter can be explicitly evaluated using integrability to all orders in the coupling. We also present compelling evidence for the universality of the generalized splitting amplitude by showing that the same function governs the double spacelike collinear limit of scattering amplitudes with up to eight particles and three loops and form factors with up to six particles and two loops.

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Phys. Rev. Lett. 135, 241601– Published 9 December, 2025
  • Received 24 July 2025
  • Revised 24 October 2025
  • Accepted 19 November 2025
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