Soft gluon exponentiation in multiparton gauge theory amplitudes
Wed, Mar. 23rd 2011, 14:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
I present a diagrammatic approach to soft-gluon exponentiation in multiparton scattering amplitudes, as reported in my recent paper with Laenen, Stavenga and White. I show that contributions to the exponent (webs) at any given order are formed through mixing between the kinematic factors and colour factors of a closed set of diagrams, where diagrams in each set are related to each other by permuting the soft-gluon attachments to the hard partons. I explain how the replica trick allows to directly determine the corresponding mixing matrices, thus solve the general problem of non-abelian exponentiation. I then show that web mixing matrices admit some remarkable properties: they are idempotent and have zero sum rows. I discuss the interpretation of these properties in view of the expected singularity structure.