Ward Identities for the Radiative Jet in QCD

Abstract

Real gluon emission from amplitudes gives rise to logarithms dependent on the kinematic threshold variable. In the soft limit these logarithms become very large, making convergence of perturbative QCD problematic. It is well understood how these leading power logarithms can be resummed. However, the logarithmic effects of next-to-leading power (NLP) in the soft momentum are not. The emission of just one soft photon or gluon can be related to the non-emitting amplitude up to NLP in the soft momentum (Low's Theorem) \cite{Low}\cite{DelDuca}. This leads to the notion of the radiative jet function. Ward identities for radiative jets are an essential tool to work out Low's theorem at NLP. In this thesis we will illustrate the various concepts involved and construct Ward identities for the radiative jet.