Journal of High Energy Physics (Jul 2025)

Integral of the double-emission eikonal function for a massive and a massless emitter at an arbitrary angle

  • Dennis Horstmann,
  • Kirill Melnikov,
  • Ming-Ming Long,
  • Andrey Pikelner

DOI
https://doi.org/10.1007/jhep07(2025)138
Journal volume & issue
Vol. 2025, no. 7
pp. 1 – 43

Abstract

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Abstract We present an analytic calculation of the integrated double-emission eikonal function of a massive and a massless emitter whose momenta are at an arbitrary angle to each other. This quantity provides one of the required ingredients for extending the nested soft-collinear subtraction scheme to processes with massive final-state particles. To calculate it, we use the standard methodology involving reverse unitarity and its extension to cases with Heaviside functions, integration-by-parts technology and reduction to master integrals, and differential equations. In addition, we also describe a semi-numerical method based on the subtraction of infra-red and collinear singularities from the eikonal function, allowing us to extract divergences of the integrated eikonal function analytically, and to derive a simple integral representation for the finite remainder.

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