Apr 25 – 30, 2022
Europe/Berlin timezone

Triple (and quadruple) soft-gluon radiation in QCD hard scattering

Apr 29, 2022, 10:00 AM
Raum Graswangtal

Raum Graswangtal


Dimitri Colferai (University of Florence)


We consider the radiation of three soft gluons in a generic process for multiparton hard scattering in QCD.
In the soft limit the corresponding scattering amplitude has a singular behaviour that is factorized and controlled by a colorful soft current.
We compute the tree-level current for triple soft-gluon emission from both massless
and massive hard partons.
The three-gluon current is expressed in terms of maximally non-abelian irreducible correlations.
We compute the soft behaviour of squared amplitudes and the colour correlations produced by the squared current.
The radiation of one and two soft gluons leads to colour dipole correlations.
Triple soft-gluon radiation produces in addition colour quadrupole correlations
between the hard partons.
We examine the soft and collinear singularities of the squared current in various
energy ordered and angular ordered regions.
We discuss some features of soft radiation to all-loop orders for processes with two and three hard partons.
Considering triple soft-gluon radiation from three hard partons, colour quadrupole interactions break the Casimir scaling symmetry between
quarks and gluons.
We also present some results on the radiation of four soft gluons from two hard partons,
and we discuss the colour monster contribution and its relation with the violation
(and generalization) of Casimir scaling.
We also compute the first correction of ${\cal O}(1/N_c^2)$ to the eikonal formula for multiple soft-gluon radiation with strong energy ordering from two hard gluons.

Primary authors

Dimitri Colferai (University of Florence) Stefano Catani (INFN Firenze)

Presentation materials