Three-loop helicity amplitudes for quark-gluon scattering in QCD
Fabrizio Caola, Amlan Chakraborty, Giulio Gambuti, Andreas von Manteuffel, Lorenzo Tancredi
Abstract
A bstract We compute the three-loop helicity amplitudes for $$ q\overline{q} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>q</mml:mi> <mml:mover> <mml:mi>q</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> → gg and its crossed partonic channels, in massless QCD. Our analytical results provide a non-trivial check of the color quadrupole contribution to the infrared poles for external states in different color representations. At high energies, the qg → qg amplitude shows the predicted factorized form from Regge theory and confirms previous results for the gluon Regge trajectory extracted from qq ′ → qq ′ and gg → gg scattering.