https://doi.org/10.1140/epjc/s10052-022-10001-z
Regular Article - Theoretical Physics
Multiple soft radiation at one-loop order and the emission of a soft quark–antiquark pair
1
INFN, Sezione di Firenze and Dipartimento di Fisica e Astronomia, Università di Firenze, Sesto Fiorentino, 50019, Florence, Italy
2
Instituto de Física Corpuscular, Consejo Superior de Investigaciones Científicas, Universitat de València, Parc Científic, 46980, Paterna, Valencia, Spain
Received:
12
September
2021
Accepted:
10
January
2022
Published online:
1
February
2022
We consider the radiation of two or more soft partons in QCD hard-scattering at one-loop order. The corresponding scattering amplitude is singular, and the singular behaviour is controlled by a process-independent soft current. Using regularization in 
space-time dimensions, we explicitly evaluate the ultraviolet and infrared divergent (
-pole) terms of the one-loop soft current for emission of an arbitrary number of soft partons in a generic hard-scattering process. Then we consider the specific case of soft quark–antiquark (
) emission and we compute the one-loop current by including the finite terms. We find that the one-loop soft- current exhibits a new type of transverse-momentum singularity, which has a quantum (absorptive) origin and a purely non-abelian character. At the squared amplitude (cross section) level, this transverse-momentum singularity produces contributions to multijet production processes in hadron collisions. The one-loop squared current also leads to charge asymmetry terms, which are a distinctive features of soft- radiation. We also extend these results to the cases of QED and mixed QCD
QED radiative corrections for soft fermion–antifermion emission.
© The Author(s) 2022
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