Theory and phenomenology of non-global logarithms

TL;DR

This paper explores the theoretical understanding and phenomenological implications of non-global logarithms in quantum chromodynamics, focusing on their effects in restricted phase space observables and methods to mitigate their impact.

Contribution

It provides a comprehensive analysis of non-global logarithms, introduces techniques to reduce their numerical significance, and applies these methods to specific event shape and energy flow observables.

Findings

Non-global logarithms significantly affect certain observables in QCD.

Clustering algorithms can reduce the impact of non-global logarithms.

Multiple observable distributions help understand and control non-global effects.

Abstract

We discuss the theoretical treatment of non-global observables, those quantities that are sensitive only to radiation in a restricted region of phase space, and describe how large `non-global' logarithms arise when we veto the energy flowing into the restricted region. The phenomenological impact of non-global logarithms is then discussed, drawing on examples from event shapes in DIS and energy-flow observables in 2-jet systems. We then describe techniques to reduce the numerical importance of non-global logarithms, looking at clustering algorithms in energy flow observables and the study of associated distribution of multiple observables.